Floriculture and Ornamental Nurseries
March 2021
PEST MANAGEMENT GUIDELINES FOR AGRICULTURE
Contents (Dates in parenthesis indicate when each topic was updated)
General Management in an IPM Program ................................................................................................................................... 1
Integrated Pest Management (3/21) .......................................................................................................................................... 1
Diagnosing Plant Problems (3/21) ............................................................................................................................................ 2
Diagnosing the Causes(s) of Unhealthy Plants (3/21) .......................................................................................................... 3
Reflective Mulches (3/21) ........................................................................................................................................................... 6
Managing Pesticide Resistance (3/09) ...................................................................................................................................... 7
Diseases (Section reviewed 11/20) ................................................................................................................................................. 9
General Information......................................................................................................................................................................... 9
Management of Soilborne Pathogens (11/20) ......................................................................................................................... 9
General Properties of Fungicides 11/20)................................................................................................................................ 13
Key Diseases .................................................................................................................................................................................... 15
Armillaria Root Rot (Oak Root Fungus) (11/20) .................................................................................................................. 15
Aster Yellows (11/20) ................................................................................................................................................................. 17
Bacterial Leaf Spots, Blights, Cankers, and Rots (11/20) .................................................................................................... 18
Black Root Rot (11/20) ............................................................................................................................................................... 20
Cottony Rot (11/20) .................................................................................................................................................................... 22
Crown Gall (11/20) ..................................................................................................................................................................... 24
Damping-Off (11/20) ................................................................................................................................................................. 26
Downy Mildew (11/20) ............................................................................................................................................................. 29
Fungal Leaf Spots, Blights, and Cankers (11/20) ................................................................................................................. 31
Fusarium Wilt (11/20) ................................................................................................................................................................ 32
Gray Mold (11/20) ...................................................................................................................................................................... 35
Phytophthora Root and Crown Rots (11/20) ......................................................................................................................... 38
Powdery Mildew (11/20) ........................................................................................................................................................... 40
Pythium Root Rot (11/20) ......................................................................................................................................................... 44
Rust (11/20) .................................................................................................................................................................................. 46
Southern Blight (11/20) ............................................................................................................................................................. 49
Sudden Oak Death and Ramorum Blight (11/20) ................................................................................................................ 51
Verticilium Wilt (11/20) ............................................................................................................................................................ 55
Viruses and Viroid Diseases (11/20) ...................................................................................................................................... 57
Disease Control Outlines .............................................................................................................................................................. 59
Aster, China (Callistephus chinensis) (11/20)................................................................................................................................ 59
Azalea (Rhododendron spp.) (11/20).............................................................................................................................................. 60
Begonia (Begonia spp.) (11/20) .................................................................................................................................................. 61
Calla (Zantedeschia spp.) (11/20) ............................................................................................................................................... 62
Camellia (Camellia spp.) (11/20) ............................................................................................................................................... 63
Carnation (Dianthus caryophyllus) (11/20) ............................................................................................................................... 64
Cattleya (Cattleya spp.) (11/20) ................................................................................................................................................. 66
Chrysanthemum (Chrysanthemum grandiflora) (11/20) .......................................................................................................... 68
Cyclamen (Cyclamen spp.) (11/20) ............................................................................................................................................ 71
Cymbidium orchid (Cymbidium spp.) (11/20) ........................................................................................................................ 72
Dahlia (Dahlia spp.) (11/20) ....................................................................................................................................................... 73
Delphinium (Delphinium spp. and hybrids) (11/20).............................................................................................................. 75
Easter Lily (Lilium longiflorum) (11/20) .................................................................................................................................... 76
Fuchsia (Fuchsia spp.) (11/20).................................................................................................................................................... 77
Geranium (Pelargonium spp.) (11/20)....................................................................................................................................... 78
Gladiolus (Gladiolus spp.) (11/20) ............................................................................................................................................ 80
Gypsophila (Gypsophila paniculata) (11/20) ............................................................................................................................. 82
Heather (Calluna vulgaris, Erica spp.) (11/20) .......................................................................................................................... 83
Iris (Bulbous) (11/20) ................................................................................................................................................................. 84
Iris (Rhizomatous) (11/20) ........................................................................................................................................................ 86
Marguerite Daisy (Chrysanthemum (=Argyranthemum) frutescens) (11/20) ......................................................................... 87
Narcissus (Narcissus spp.) (11/20) ............................................................................................................................................ 88
Peony (Paeonia spp.) (11/20) ...................................................................................................................................................... 90
Poinsettia (Poinsettia spp.) (11/20) ............................................................................................................................................ 91
Pot Marigold (Calendula officinalis) (11/20) ............................................................................................................................. 93
Rose (Rosa spp.) (11/20) ............................................................................................................................................................. 94
Shasta Daisy (Chrysanthemum maximum) (11/20)................................................................................................................... 96
Snapdragon (Antirrhinum majus) (11/20) ................................................................................................................................ 97
Statice (Limonium spp.) (11/20) ................................................................................................................................................. 98
Stock (Matthiola spp.) (11/20) .................................................................................................................................................... 99
Strawflower (Helichrysum bracteatum) (11/20) ...................................................................................................................... 101
Sweet Pea (Lathyrus odoratus) (11/20)..................................................................................................................................... 102
Sweet William (Dianthus barbatus) (11/20) ........................................................................................................................... 103
Host-Pathogen Index (11/20) ...................................................................................................................................................... 104
Insects, Mites, and Other Invertebrates (Section reviewed 3/09) ........................................................................................ 109
General Information..................................................................................................................................................................... 109
Common Signs and Symptoms on Plants Damaged by Pest Insects, Mites, Slugs, and Snails (Arthropods) and
the Probable Causes (3/21) ..................................................................................................................................................... 109
Monitoring With Sticky Traps (3/21) ................................................................................................................................... 111
Establishing Action Thresholds (3/21)................................................................................................................................. 113
Biological Control (3/21) ......................................................................................................................................................... 115
Insect, Mite, and Other Invertebrate Management ................................................................................................................ 117
Aphids (05/10) ........................................................................................................................................................................... 117
Armored Scales (5/10).............................................................................................................................................................. 121
Armyworms and Cutworms (5/10) ....................................................................................................................................... 123
Bulb Mites (3/09) ...................................................................................................................................................................... 126
Cabbage Looper (5/10) ............................................................................................................................................................ 127
Diamondback Moth (5/10) ..................................................................................................................................................... 129
Foliar-Feeding Mealybugs (5/10) .......................................................................................................................................... 131
Fungus Gnats (3/09) ................................................................................................................................................................. 134
Leafhoppers and Sharpshooters (5/10) ................................................................................................................................ 137
Leafminers (5/10) ...................................................................................................................................................................... 141
Leafrollers (5/10)....................................................................................................................................................................... 143
Root Mealybugs (5/10) ............................................................................................................................................................ 146
Shore Fly (5/10) ......................................................................................................................................................................... 148
Snails and Slugs (3/21) ............................................................................................................................................................ 150
Soft Scales (5/10) ...................................................................................................................................................................... 154
Thread-footed (Tarsonemid) Mites (5/10) ........................................................................................................................... 156
Thrips (5/10) .............................................................................................................................................................................. 158
Twospotted Spider Mites (5/10) ............................................................................................................................................ 161
Whiteflies (5/10) ....................................................................................................................................................................... 164
Nematodes (Section reviewed3/21) ........................................................................................................................................... 168
Weeds (Section reviewed 7/20) ................................................................................................................................................... 174
Common And Scientific Names Of Weeds In Floriculture And Nurseries (7/20) ...................................................... 174
General Methods Of Weed Management (7/20) ................................................................................................................ 176
Susceptibility Of Weeds To Herbicide Control (7/20)...................................................................................................... 180
Container Nurseries ..................................................................................................................................................................... 183
Integrated Weed Management For Container Nurseries (7/20) ...................................................................................... 183
Special Weed Problems For Container Nurseries (7/20) .................................................................................................. 186
Herbicide Treatment Table For Containers And Field-Grown Trees And Shrubs (7/20) ......................................... 188
Field-Grown Trees and Shrubs .................................................................................................................................................. 193
Integrated Weed Management For Field-Grown Trees And Shrubs (7/20) ................................................................. 193
Special Weed Problems For Field-Grown Trees And Shrubs (7/20).............................................................................. 194
Herbicide Treatment Table For Containers And Field-Grown Trees And Shrubs (7/20) ......................................... 195
Field-Grown Flowers ................................................................................................................................................................... 196
Integrated Weed Management For Field-Grown Flowers (7/20) .................................................................................... 196
Herbicide Treatment Table For Field-Grown Flowers (7/20) .......................................................................................... 198
Greenhouse-Grown Crops .......................................................................................................................................................... 201
Integrated Weed Management Inside Greenhouses (7/20) ............................................................................................. 201
Special Weed Problems Inside Greenhouses (7/20) .......................................................................................................... 202
Herbicide Treatment Table For Inside Greenhouses (7/20) ............................................................................................ 203
Integrated Weed Management Outside Greenhouses (7/20) .......................................................................................... 204
Herbicide Treatment Table For Outside Greenhouses (7/20) ......................................................................................... 205
Precautions For Using Pesticides ............................................................................................................................................... 207
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Authors and Credits
Suggested Citation
Wilen CA, Koike ST, Ploeg A, Tjosvold SA., Bethke JA, Mathews DM, Stapleton JJ. Revised continuously. UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries. UC ANR Publication 3392. Oakland, CA.
Crop Team: C.A. Wilen (emeritus), UC IPM Program, UCCE San Diego Co. (Crop Team Leader and UC
IPM Facilitator); S.T. Koike (emeritus), TriCal Diagnostics, Hollister; A.T. Ploeg, Nematology, UC
Riverside; S.A. Tjosvold (emeritus), UCCE Santa Cruz Co.
Diseases: S.T. Koike, (emeritus), TriCal Diagnostics, Hollister; S.A. Tjosvold (emeritus), UCCE Santa
Cruz Co., D.M. Mathews, Plant Pathology, UC Riverside
Insects, Mites, and Other Invertebrates: J.A. Bethke (emeritus), UCCE San Diego; C. A. Wilen (emeritus),
UC IPM Program, UCCE San Diego Co. (Snails and Slugs)
Acknowledgment for contributions to Insects and Mites: K.L. Robb, UCCE Mariposa Co.; H.S. Costa,
Entomology, UC Riverside; R.S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT;
M.P. Parrella (emeritus), Entomology, UC Davis
Nematodes: J.J. Stapleton, UC IPM Program, Kearny Agricultural Center; A.T. Ploeg, Nematology, UC
Riverside
Acknowledgment for contribution to Nematodes: J. Ole Becker, UC Riverside; Becky B. Westerdahl, UC
Davis; M.V. McKenry (emeritus), Kearney Agricultural Center, Parlier
Weeds: C.A. Wilen (emeritus), UC IPM Program, UCCE San Diego Co.
Acknowledgment for contributions to Weeds: L.R. Oki, UC Davis; T.M. Bean, UC Riverside; C.L. Elmore
(emeritus), Vegetable Crops/Weed Science, UC Davis
About this publication
Produced and edited by:
UC Statewide IPM Program
University of California, Agriculture and Natural Resources
Coordinator
P. Kosina, UC IPM
S.H. Dreistadt, UC IPM
Production
F.G. Rosa
This material is partially based on work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Crop Protection and Pest Management Competitive Grants Program.
These guidelines represent the best information currently available to the authors and are intended to help you make the best
choices for an IPM program. Not all formulations or registered pesticides are mentioned. Always read the label and check with local
authorities for the most up-to-date information regarding registration and restrictions on pesticide use. Check with your agricultural commissioner for latest restricted entry intervals.
To be used with UC ANR Publication 3402, Integrated Pest Management for Floriculture and Nurseries
This publication has been anonymously peer reviewed for technical accuracy by University of California
scientists and other qualified professionals. This review process was managed by the ANR Associate Editor
for Agricultural Pest Management.
The UC IPM Pest Management Guidelines are available from:
• Online: http://ipm.ucanr.edu
• UC Cooperative Extension County Offices
March 2021
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
General Management in an IPM Program
INTEGRATED PEST MANAGEMENT (3/21)
Integrated pest management (lPM) is an ecosystem-based strategy that focuses on long-term suppression
of pest abundance and prevention of pest damage through a combination of control strategies. Management actions are taken according to established guidelines or action thresholds after monitoring indicates
that control action is warranted. IPM requires knowledge of pest life cycles and pertinent biology and an
understanding of crop production. Pesticides when warranted are selected and applied in ways that minimize risks to workers and other persons, beneficial and nontarget organisms, and the environment (e.g.,
air and water quality). The goal is to suppress the abundance of, or exclude or remove, only the target organism(s) while maintaining the economic viability of the cropping system. Collectively all measures
taken under an IPM strategy should attempt to minimize economic crop losses and environmental impact
while simultaneously minimizing control efforts such that overall profitability is maximized.
Key components of an IPM program in general order of implementation are:
• Take preventive control measures, the start-clean and grow-clean strategy.
• Monitor crops regularly.
• Accurately identifying pests and their natural enemies and correctly diagnose the cause(s) of
plant problems.
• Develop thresholds or guidelines for when and how to take control actions.
• Take appropriate and effective actions, generally both non-chemical and chemical controls in
combination.
For more information see What is Integrated Pest Management (IPM), For Retail Nurseries & Garden Centers,
and University of California (UC) Agriculture and Natural Resources (ANR) printed publications that
include Container Nursery Production and Business Management Manual, Integrated Pest Management for Floriculture and Nurseries, and Water, Root Media, and Nutrient Management for Greenhouse Crops.
General Management in an IPM Program
Integrated Pest Management (3/21) 1
Illustrated version at https://www2.ipm.ucanr.edu/agriculture/floriculture-and-ornamental-nurseries/
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
DIAGNOSING PLANT PROBLEMS (3/21)
Diagnosis is the art and science of identifying the cause of the plant problem under investigation. Problem causes can be
• abiotic (cultural and environmental) including chemical injury, inappropriate temperatures or
soil moisture, mechanical injury, nutrient deficiency or excess, and salt damage
• biotic (living organisms, pests) including insects, nematodes, mites, mollusks, plant pathogens,
and weeds
• combinations of causes including both abiotic and biotic (e.g., drought stress and spider mite
damage) or a pest insect and plant pathogen it vectors (glassy-winged sharpshooter and Xylella
fastidiosa)
To diagnose the cause(s) of unhealthy plants
• Ask and answer appropriate questions to define the problem and obtain information relevant to
the situation under investigation. See DIAGNOSING THE CAUSE(S) OF UNHEALTHY PLANTS
for a detailed example of this.
• Thoroughly examine the plants, production areas, and plant care practices.
• Use appropriate field diagnostic (quick-test) kits and properly collected samples for laboratory
analyses of specific, suspected causes of abiotic and biotic maladies.
• Compile the information and consult additional references and resources including local University of California Cooperative Extension (UCCE) Advisors and their publications.
• Make an informed diagnosis.
For example, to diagnose whether an insect is the cause of damage, it is important to
• Learn the pest's life cycle.
• Be able to identify each of development stages of the pest.
• Know how that pest feeds on the crop or otherwise damages plants.
• Learn which pest life stages are susceptible to the available management methods.
Note that the most apparent life stage (e.g., flying adults captured in sticky traps, or adult female pests)
can differ from the stage(s) that feed on and damage plants and are susceptible to control actions (commonly the immatures, larvae or nymphs). To help you diagnose pest problems, consult COMMON
SIGNS AND SYMPTOMS ON PLANTS DAMAGED BY PEST INSECTS, MITES, SLUGS, AND SNAILS
(ARTHROPODS) AND THE PROBABLE CAUSES.
See DIAGNOSING THE CAUSE(S) OF UNHEALTHY PLANTS for a detailed example.
General Management in an IPM Program
Diagnosing Plant Problems (3/21)
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Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
DIAGNOSING THE CAUSES(S) OF UNHEALTHY PLANTS
(3/21)
Diagnosing the cause(s) of plant problems can be done by asking a series of pertinent questions and investigating the answers:
Questions About the Plant
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What are the genus, species, and cultivar of the plant in question?
Is this particular plant suited to the production area?
Is the cultivar resistant or especially susceptible to diseases or other problems?
Is the plant sensitive to certain environmental factors (e.g., salinity, excess or deficient soil moisture)?
How does the plant normally appear when grown under various conditions (full sun,
shadehouse, greenhouse, coastal versus inland production locations, winter versus summer) or at
different stages of growth and development?
What is the normal growth rate?
What are the characteristics, appearance, and growth habits of a healthy plant, and could these
features be confused with an unhealthy plant?
Questions About the Symptoms
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What are the symptoms of the affected plant?
What plant parts are affected?
Are symptoms restricted to external plant surfaces or are there also internal symptoms (vascular
streaking, discolored crown tissue)?
Are symptoms present only on exposed plant surfaces or also on protected covered tissues such
as unexpanded inner leaves or unopened flowers?
What is the distribution of the symptoms on any one particular plant (do symptoms occur on one
side of the plant, only on older or newer leaves, on secondary roots but not on primary roots,
etc.)?
How did the symptoms first start?
How do early symptoms differ from more advanced symptoms?
How long have the symptoms been present?
What is the extent (distribution and severity) of symptoms in the population of plants of a given
species or cultivar?
Growth Stage
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What is the growth stage of the affected plant (seedling, cutting, newly transplanted, mature
flowering or fruiting plant, senescent plant)?
Is a particular growth stage associated with the problem?
What was the condition of the plant when first placed in the production area?
How does the growth rate of the affected plant compare to that of a healthy plant?
Symptoms on Other Plants
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Are symptoms restricted to one species or one cultivar of plant?
Do the same symptoms occur on one type of plant that is located in different growing areas?
Alternatively are there different plantings of the same plant type that are symptomless?
What other plant species and cultivars appear affected?
Do adjacent plantings, weeds, or nearby landscape plants exhibit similar symptoms?
If other plants are affected, do they belong to a common group or family of plants?
Patterns
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How are the symptoms distributed within the specific production area(s) of concern?
Are there patterns (repeating numbers of plants or plant rows) to the symptoms or do symptoms
occur randomly throughout the planting?
Are symptomatic plants found in clustered groups?
General Management in an IPM Program
Diagnosing the Cause(s) of Unhealthy Plants (3/21)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
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Do the symptoms occur in lines, streaks, or circles?
Are symptomatic plants found mostly along the edges of the planting?
Are affected plants next to buildings, ditches, roads, weedy areas, or other crops or production
areas?
Are symptoms associated with subsets of plants within the planting, indicating an association
with plants from certain transplant trays, different sources of plant material, or other production
factors?
Are symptoms associated with physical features at the nursery, such as low or high spots of the
field, places where water does not drain well, presence or absence of underlying gravel, or particular soil types?
Do such areas become flooded after rains or receive irrigation runoff?
Are affected areas under sprinklers or watered by drip irrigation?
Timing
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What temporal factors are important?
When did the symptoms first occur?
Are there various stages of symptoms indicating new infections versus older ones?
Have the features or severity of the symptoms changed over time?
Do symptoms appear to have developed gradually over a period of time or rapidly and all at
once?
Biotic or Abiotic
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Do symptoms resemble those caused by biotic agents, such as pathogens, nematodes, arthropods,
or vertebrate pests?
Alternatively, are symptoms more suggestive of physiological or abiotic factors, such as nutritional problems, physiological disorders, genetic mutations (chimeras), chemical damage, or environmental extremes?
Do the symptoms provide evidence that more than one factor or pathogen is involved?
Signs
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A sign is the visible presence of a causal agent or factor. Are such signs present?
Examples of signs are bacterial ooze, chemical residue, fungal growth (e.g., mycelia or spores),
and insect bodies or excrement (frass).
Are there multiple signs indicating that more than one factor may be involved?
What is the distribution of signs on the affected plant (present on all or only on certain plant
parts)?
Are signs present on all symptomatic plants and do they appear to be associated with the symptoms?
Are signs present on adjacent plantings or nonsymptomatic plants?
Timing and Context
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What time of year did the problem occur?
If the problem occurred before, did it take place during the same time of year?
What are the current and past weather conditions?
Have there been any unusual weather patterns or developments recently or in the past few weeks
or months?
Have there been any conditions that would hinder plant growth or favor arthropod or pathogen
development?
Is there evidence of abiotic stress factors (e.g., mineral deficiencies and toxicities, pollution, temperature extremes, salt buildup, water stress or excess, wind or other mechanical damage, etc.)?
What is the general location of the nursery (coastal versus inland, next to other crops or nurseries,
next to roads, etc.)?
Biotic Factors
•
Which arthropod pests, nematodes, pathogens, snails and slugs, and vertebrate pests are known
to occur on the host or cause feeding damage or other injury to the host?
General Management in an IPM Program
Diagnosing the Cause(s) of Unhealthy Plants (3/21)
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Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
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Which biotic agents occur in the geographic area of concern?
Compile a list of common pests that occur in the area and may be the cause(s) of the current
problems. For sources of this information see COMMON SIGNS AND SYMPTOMS ON PLANTS
DAMAGED BY PEST INSECTS, MITES, SLUGS, AND SNAILS (ARTHROPODS) AND THE
PROBABLE CAUSES, the "Crop Tables" at the back of Integrated Pest Management for Floriculture and Nurseries and the similar information online: Flowers; Fruit Trees, Nuts, Berries, and
Grapevines; Trees and Shrubs; and Vegetables and Melons.
Source: Container Nursery Production and Business Management Manual. See this publication for more
detailed help with problem diagnosis, such as example answers and problem-solving steps for the questions above.
General Management in an IPM Program
Diagnosing the Cause(s) of Unhealthy Plants (3/21)
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Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
REFLECTIVE MULCHES (3/21)
Reflective mulch delays or prevents certain flying insects from infesting plants because reflected ultraviolet light confuses insects’ ability to locate their hosts. Reflective mulches have been effectively used to
greatly reduce colonization of young crops by winged aphids, leafhoppers, thrips, and whiteflies. Although few floral crops have been studied, reflective mulches have been shown to be effective in various
vegetable row crops against melon aphid, silverleaf whitefly, and western flower thrips. In field-grown
crops especially sensitive to viruses or other insect-vectored pathogens, the added cost of reflective mulch
may be justified because the mulch can be significantly more effective than insecticides in preventing
pathogen infection. Insects that migrate onto a crop often have time to feed long enough to transmit viruses before being killed by pesticide residue on treated crops; reflective mulches can prevent such pests
from alighting on the crop. Reflective mulches also conserve soil moisture and can improve crop growth
beyond that provided by pest control, possibly due to warmer night soil temperatures, additional available soil moisture, more even soil moisture, and increased (reflected) light levels.
Reflective mulch is most effective during early growth when plants are small. As plants grow larger, reflective mulch becomes less effective and other management methods may be warranted. Reflective
mulches cease to repel insects when the plant canopy covers more than about 60% of the soil surface.
Note that working around reflective mulches can be annoying to workers and require protective eyewear.
Transplant through holes in the mulch or apply the mulch before seeded plants emerge from the soil by
leaving a thin mulch-free strip of soil along the planting row. Reflective mesh is also available for application over the top of a crop; light-weight material is lifted as plants grow. Various materials, such as plastic
(polyethylene or nylon) film, can be used. Silver or gray are the most effective colors for reflective mulch
or mesh. White also works, but may not sufficiently suppress weed growth beneath it. Commercially
available products include aluminum-metalized or silver embossed polyethylene. Aluminum foil is also
effective, but it is expensive, delicate to handle, and not economically feasible on a large scale. Reflective
material can also be sprayed onto planting beds.
General Management in an IPM Program
Reflective Mulches (3/21) 6
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
MANAGING PESTICIDE RESISTANCE (3/09)
Pesticide resistance can become a problem when the same chemicals are used over and over to control a
particular pest. After a period, the pest may develop resistance to a chemical so that the chemical no
longer effectively controls the pest at the same rate, and higher rates and more frequent applications become necessary until eventually the chemical provides little or no control. The best way to manage pesticide resistance is to focus on three strategies: avoid, delay, and reversal. Avoid the development of pesticide resistance problems with the use of Integrated Pest Management (IPM) programs, which reduce reliance on chemical control. Delay resistance by using pesticides only when needed, as indicated by monitoring, and when pests are at a susceptible stage. Delay can also be achieved by using pesticides from different chemical classes (e.g., organophosphates, carbamates, pyrethroids, biologicals, etc.) and rotating
their use. Reversal of some resistance can occur by allowing time between applications of a class of pesticide to permit resistant populations to become diluted by pesticide-susceptible individuals. Key elements
of resistance management include minimizing pesticide use, avoiding tank mixes, avoiding persistent
chemicals, and using long-term rotations of pesticide from different chemical classes.
Minimize Pesticide Use. Minimizing pesticide use is fundamental to pesticide resistance management.
IPM programs incorporating pest monitoring in California, New York, Maryland, Canada, and elsewhere
have demonstrated 25 to 50% reduction in pesticide use with an increase in crop quality. Ask your farm
advisor for information on setting up and maintaining an IPM monitoring program. Such a program will
help determine the best application timing for pesticides (when they will do the most good), thus helping
to reduce the number of applications.
The use of nonchemical strategies, such as pest exclusion (e.g., screening), host-free periods, crop rotation,
biological control, and weed control may reduce the need to use chemicals and consequently slow the development of pesticide resistance.
Avoid Tank Mixes. Avoid combinations (mixes) of two insecticides or miticides in a single application.
Especially avoid mixing two insecticides with the same mode of action, such as the organophosphates
acephate and malathion; this increases selection for resistant pests. Such a 'super dose' often increases the
chances of selection for resistant individuals. In some cases, mixing pesticides from two different classes
provides superior control. However, long-term use of these two-class pesticide mixes can also give rise to
pesticide resistance, if resistance mechanisms to both pesticides arise together in some individuals. Continued use of the mixture will select for these multiple-pesticide-resistant pests.
In specific situations the simultaneous application of two different types of chemicals may be necessary,
but even in these cases tank mixes should be avoided. For example, insect growth regulators (IGRs) only
control the immature stages of insects. If the adult stage must also be controlled, it will be necessary to
apply another insecticide. Rather than applying an adulticide in the same manner as the IGR, however,
choose a formulation that requires a different type of application. For instance, if the IGR is applied as a
spray, it would be preferable for the adulticide to be applied as an aerosol or smoke with rapid kill of the
adults and little residual that might select for resistance buildup in surviving immatures.
Avoid Persistent Chemicals. Insects with resistant genes will be selected over susceptible ones whenever
insecticide concentrations kill only the susceptible pests. An ideal pesticide quickly disappears from the
environment so that persistence of a 'selecting dose' does not occur. When persistent chemicals must be
used, consider where they can be used in a rotation scheme to provide the control needed and with a
minimum length of exposure. One example of a persistent material that must be carefully timed to avoid
prolonged exposure is the use of imidacloprid for control of whiteflies on poinsettias. Application of this
material early in the crop prolongs the exposure of the whitefly population to this material. It may be best
to use natural enemies and/or insect growth regulators early in the crop followed by imidacloprid, if
needed. Applications that are too late do not allow the plant to adsorb the material to provide effective
control. The best time to apply this material is not later than 3 weeks before poinsettia color initiation.
Use Long-term Rotations. Resistance management strategies for insects, weeds, and fungal pathogens all
include rotating classes of pesticides (e.g., pesticides with the same mode of action such as pyrethroids,
organophosphates, carbamates, etc.). Pesticides with the same modes of action have been assigned the
same group number by their respective pesticide resistance action committees (IRAC [Insecticide Resistance Action Committee], FRAC [Fungicide Resistance Action Committee], and HRAC [Herbicide Resistance Action Committee]). These group numbers have been included in the treatment tables of this
guideline to help clarify when rotating pesticides, which ones can be rotated. However, the strategies
General Management in an IPM Program
Managing Pesticide Resistance (3/09)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
used in rotations differ. For example, with fungicides, it is suggested that classes be rotated every application. With insecticides, a single chemical class should be used for a single generation of the target pest followed by a rotation to a new class of insecticide that will affect the next generation and any survivors
from the first generation. Longer use of a single chemical class will enhance the chance of resistance since
the survivors of the first generation and the next will most likely be tolerant to that class. Rotating
through many chemical classes in successive generations will help maintain efficacy.
If there is only one chemical that is effective against a pest and other available products are only marginally effective, a good strategy to follow is to use the marginally effective materials at times when pest
pressure is less severe and to reserve the effective material for those periods of time when control must be
most effective. For more information watch the videos on Fungicide Resistance Management, Herbicide
Resistance Management, and Insecticide Resistance Management.
General Management in an IPM Program
Managing Pesticide Resistance (3/09)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Diseases
(Section reviewed 11/20)
General Information
MANAGEMENT OF SOILBORNE PATHOGENS (11/20)
Soil is a reservoir for many plant pathogens and plants are under regular attack by these soilborne organisms. If inoculum levels are high enough and environmental conditions become favorable for infection,
susceptible plants will develop disease. Soilborne pathogens are readily spread if infested soil or contaminated water moves into other fields or planting areas. Levels of soilborne pathogens, including bacteria,
fungi, nematodes, and some viruses can be reduced in the soil by appropriate treatments.
Learn which pathogens attack the crop to be grown. Examine the crop regularly, at least weekly, for
symptoms of disease or signs of pathogens.
To monitor for root diseases in floriculture and ornamental nurseries
• Select a few plants from different locations, remove plants from their containers, and gently
scrape or wash away soil.
• Examine roots and crowns for discoloration, softness, shriveling, or other early indications of disease.
• Know what healthy roots look like so diseased roots can be detected early. Healthy root characteristics may change or be different depending on species, root age, or growing conditions.
• Look for discolored or wilted plants and fungal growths aboveground, which may indicate more
advanced stages of disease.
• Use test kits in combination with other information to make good pest management decisions.
Test kits are readily available for detecting Phytophthora pathogens infecting greenhouse and container-grown nursery plants. Agdia (Elkhart, IN) supplies simple immunological test kits that detect Phytophthora species in minutes. A positive detection can usually help with the diagnostic
process and get you quickly on the path to managing the problem. Sometimes, however, a positive result might be deceiving because these tests are not entirely accurate and can occasionally
react to certain Pythium or Phytopythium species. These latter two groups of species may or may
not be the primary cause of root disease or even a problem at all. Some of these are soil microbes
that only break down already dead material, and many we do not fully understand yet. A nonpositive reaction of the immunological test might be deceiving also. Sometimes the tested root
tissue may not have been sampled from infected root pieces, and certain Phytophthora species do
not react with the tests.
• Send a sample of diseased plants and their roots to an appropriate laboratory to test for the presence and identification of pathogens. Proper diagnosis is vital to making the correct management
decisions.
Understand the conditions and practices that promote disease and regularly examine for and remedy disease-promoting conditions and practices. Poor sanitation, inadequate drainage, and improper irrigation
are the primary conditions that promote diseases of roots. Remove crop residue and old or low-quality
plants that will not be marketed.
Soil Solarization
In warmer climatic areas, solarization has been effective for disinfesting containerized soil or growing
medium, soil in cold frames, and soil in open fields.
For soil in containers
• Use either in bags or flats covered with transparent plastic or in layers 3- to 9-inches wide sandwiched between two sheets of plastic to solarize planting media. A double layer of plastic can increase soil temperature by up to 50°F.
Diseases: General Information
Management of Soilborne Pathogens (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
•
•
Monitor the temperature of the growing medium closely by placing a temperature-measuring
probe into the center of the mass of the soil mix to ensure the temperature is high enough to control pests.
In warmer areas of California, soil inside black plastic sleeves can reach 158°F (70°C) during solarization, equivalent to target temperatures for soil disinfestation by aerated steam. At this temperature, soil is effectively solarized within 30 minutes. At 140°F (60°C), soil is solarized in 1
hour.
In open fields, soil is more easily covered with a single layer of transparent plastic. Soil temperatures will
be highest at the soil surface (first 12 inches). The plastic needs to be left in place for 4 to 6 weeks. For
maximum effectiveness and treatment predictability, solarize open fields only in warmer climatic areas,
unless previous testing has given consistently desirable results. The effectiveness of solarization, especially in cooler climatic areas, can be improved by adding various botanical products containing glucosinolates, such as mustard seed meal, broccoli, and cabbage. Solarization is acceptable where a non-chemical
approach is desired.
Heat
Heating the soil is very effective and the soil can be used immediately after cooling, unlike chemically
treated soil. Many plant pathogens are killed by short exposures to high temperatures. Most plant pathogens can be killed by temperatures of 140°F (60°C) for 30 minutes. However, some viruses such as Tobacco
mosaic virus (TMV) may survive this treatment. Where weed seeds are a problem, a higher treatment temperature is required, and even then, some weed seeds may still survive.
Although pure steam at sea level is at 212°F (100°C), the temperature of the steam used to treat soil is usually about 180°F because of air that is present in the steam or soil being treated. If air is mixed with steam,
the temperature of the steam-air mixture can be closely controlled, depending on the ratio of air to steam.
It has been demonstrated that some diseases, such as Rhizoctonia damping-off, are much less severe in soil
that has been treated at 140°F rather than at 180°F. Experience will tell the grower which temperature will
best treat the soil, but as a starting point try 140°F (60°C) for 30 minutes.
If a cement mixer is used to heat a bulk quantity of soil, generally it is not necessary to introduce air into
the steam because a large amount of air is present in the mixer and the temperature can be controlled by
simply regulating the flow of steam. Expensive air blowers are not required for this method.
Steam heating of containers filled with soil in vaults likewise may not require the introduction of air into
the steam to control the temperature. However, circulation within the vault is important to ensure even
distribution of heat. Circulating fans can be located within, or external to, the vault and the steam can be
introduced into the recirculating air. Leave space between the vaults and check temperatures throughout
the vault to ensure that there is good circulation of steam air.
Soil Fumigants
Only three fumigants with very limited suitability for soil fumigation remain allowed in California. Registered fumigants are chloropicrin, 1,3-dichloropropene (1,3-D), and methyl isothiocyanate (MITC) generators such as metam sodium, metam potassium, and Basamid. However, these products have many
statewide regulatory restrictions and are also subject to local regulations. In the absence of methyl bromide, the most promising registered fumigants are chloropicrin alone or chloropicrin mixed with 1,3-dichloropropene applied sequentially in combination with metam sodium or metam potassium. These fumigants can be applied to the raised beds through drip irrigation systems. In drip fumigation, it is critical
to distribute the water evenly throughout the field and throughout the target soil treatment zone. Chloropicrin and 1,3-dichloropropene should not be applied simultaneously with metam sodium to avoid their
rapid degradation in the irrigation water. Only certified applicators can apply fumigants.
Metam-sodium (Vapam), and dazomet (Basamid) alone are not very effective for controlling many soilborne pathogens, including Verticillium and Fusarium oxysporum. See the Activity of Soil Fumigants table
for how effective each fumigant is against various types of pests.
Chloropicrin (trichloronitromethane) is the best fumigant for controlling Verticillium dahliae. In the past it
was combined with methyl bromide in various mixtures depending upon the organisms in the soil. If
used alone, a water seal may be used to confine the gas; however, the gas is very objectionable and irritating (it is commonly known as tear gas) and, if not effectively confined, it may drift to inhabited areas.
Diseases: General Information
Management of Soilborne Pathogens (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
This is a restricted use material and requires a permit from the county Agricultural Commissioner to be
purchased or applied.
Activity of soil fumigants.
Common name
chloropicrin
Activity against
Nematodes
Fungi
fair
excellent
fair
excellent
fair
excellent
excellent
very good
excellent
excellent
excellent
excellent
excellent
excellent
good
good
good
good
good
good
good
good
good
good
Trade name
TriClor
TriClor EC
Telone II
Telone C35
InLine
Pic-Clor60
Pic-Clor60EC
Vapam HL
Sectagon 42
K-Pam HL
Sectagon-K54
Basamid
1,3-dichloropropene
1,3 dichloropropene plus chloropicrin
chloropicrin plus 1,3 dichloropropene
metam sodium
metam potassium
dazomet
Weeds
poor
fair*
fair
fair
good*
good*
good*
good
good
good
good
good
* Using high rates or retentive plastic mulch (especially totally impermeable film) improves weed control.
Soil Fungicides
Some fungicides work best if incorporated before planting. Others may be incorporated or applied after
sowing or planting. Some soil fungicides control a narrow range of organisms while others control a wide
range of organisms. Some of the narrow range chemicals are the most effective in controlling a specific
organism. Combinations are used to increase the number of organisms controlled.
The Examples of Conventional and Biological Fungicides table is not a complete list of available and active fungicides against soilborne pathogens. It provides examples of conventional and biological fungicides.
Salts or esters of phosphorous acid (Aliette)
Gliocladium virens
(SoilGard)
Iprodione
(Chipco 26019)
Mefenoxam
(Subdue Maxx)
PCNB - pentachloronitrobenzene or quintozene (Terraclor)
Streptomyces griseoviridis
(Mycostop)
Thiabendazole
(Mertect)
Thiophanate-methyl
(Talaris)
C
C
Diseases: General Information
C
C2
C
C
C
N
Seed rot
Sclerotium rolfsii
Sclerotinia
Root & stem rot
P
C
C
Rhizoctonia
Pythium
Phytophthora
Penicillium blue mold
Fusarium sp.
Foliar downy mildew
Damping-off
Cylindrocladium spp.
Cottony rot
Black root rot
Common name
(Example trade name)
Alternaria and Phomopsis wilt
Examples of conventional and biological fungicides.
C
C
C
C
C
C
N
N
C
P1
P1
P1
N
N
C
C
C
C
C2
N
Management of Soilborne Pathogens (11/20)
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Trichoderma spp.
(RootShield)
C
C
C
Triflumizole
C
(TerraGuard)
C = control; P = partial control/suppression; N = no control
1 In the greenhouse it may suppress root rots of Pythium, Phytophthora, and Rhizoctonia.
2 Used for bulb or corm dips to control Fusarium basal rot and Penicillium blue mold
Seed Treatments
Streptomyces griseoviridis (Mycostop) is used as a seed treatment for damping-off and early root rots for
ornamentals planted in fields or greenhouse. Captan is also a seed treatment, but offers only a limited
protection.
Treatment of Containers and Equipment
Debris, soil, and plant material cling to containers and equipment; thoroughly wash equipment to remove all soil or planting mix particles. Heat treatment is effective in killing the plant pathogens that adhere to containers or that are in the debris. Where steam is not available, hot water or solarization can be
very effective. Most plastic can be treated with hot water at temperatures that cause minimal softening.
The minimum water temperature should be 140°F (60°C) whenever possible. Treatment time can be as
short as 1 minute. Longer treatment times are more reliable, and the container or equipment must reach
at least 140°F (60°C). For solarization, containers should be moistened, stacked, and placed beneath a
double-layer tent. Incubate for 30 minutes at or above 158°F (70°C), or 1 hour at or above 140°F (60°C).
Sodium hypochlorite (the active ingredient in bleach) is effective in killing most types of fungal spores
and bacteria. However, it penetrates clinging soil and plant material very poorly. It is effective only as a
surface disinfectant, so containers, tools, etc. must be free of soil and plant material and clean before treatment. Sodium hypochlorite is generally used as a surface disinfectant at 0.5%. To achieve this concentration of sodium hypochlorite, household bleach can be diluted 1 part bleach to 9 parts water. For known
contaminated materials, a stronger solution diluted 1 part bleach to 4 parts water (1% sodium hypochlorite), may be more effective in killing pathogens. Allow the solution to be in contact with nonporous
materials for a minimum of 5 to 10 minutes, then rinse well with clean water to remove bleach and avoid
phytotoxicity. Bleach dilutions must be made fresh each day because once diluted, the effectiveness of the
solution diminishes over time (50% loss occurs every 2 hours). Debris, potting mix, and other residues left
over in bleach washes will also greatly reduce bleach concentration and effectiveness.
Quaternary ammonia compounds are excellent bactericides and viricides and are effective in killing some
kinds of fungal spores. They penetrate plant material and soil poorly, so containers, tools, etc. must be clean
before treatment.
Diseases: General Information
Management of Soilborne Pathogens (11/20)
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GENERAL PROPERTIES OF FUNGICIDES 11/20)
Common name
(trade name)
ametoctradin/dimethomorph
(Orvego)
azoxystrobin (Heritage)
boscalid/pyraclostrobin (Pageant)
Chemical class
QoSI/carboxylic acid amides
Activity
systemic
(local)
single-site
multi-site
Qol2
carboximide/QoI2
Resistance
potential
low
11
7/11
high
medium
M 04
low
M 05
21
low
—
Captan (Captan)
phthalimides
chlorothalonil (Daconil)
cyazofamid (Segway)
chloronitrile
cyanoimidazole
cyprodinil/fludioxonil (Palladium)
dicloran (Botran)
dimethomorph (Stature)
etridiazole (Terrazole CA)
fenamidone (Fenstop)
anilinopyrimide/phenylpyrrole contact
9/12
aromatic hydrocarbon
systemic (local) 14
carboxylic acid amines
—
40
heteroaromatic
—
14
QoI2-imidazolinones
contact
11
low to medium
medium
low-medium
low-medium
high
fenhexamid (Decree)
fixed copper (Kocide)
fludioxonil (Medallion)
fluopicolide (Adorn)
hydroxyanilide
inorganic
phenylpyrroles
pyridinylmethyl-benzamides
—
multi-site
—
systemic
(locally)
17
M 01
12
43
low-medium
low
low-medium
low
fluoxastrobin (Disarm)
QoI2–dihydro-dioxazines
systemic
11
high
flutolanil (Prostar)
succinate-dehydrogenase
inhibitor
biological
dicarboximide
inorganic
—
7
medium
—
multi-site
multi-site
NC
2
M 02
low
medium-high
low
Gliocladium virens (SoilGard)
iprodione (Chipco 26019 N/G)
lime sulfur
multi-site
(contact)
multi-site
contact
Mode of
action1
45/40
mancozeb (Dithane)
dithio-carbamate (EBDC)4
mandipropamid (Micora)
mandelic acid amides
mefenoxam (Subdue Maxx)
acylalanine
myclobutanil (Rally)
DMI3-triazole
neem oil (Triact)
oil
PCNB (Terraclor)
aromatic hydrocarbon
piperalin (Pipron)
amines
potassium bicarbonate (Kaligreen)
inorganic
propiconazole (Banner Maxx)
DMI3-triazole
Reynoutria sachalinensis - knotweed, biological
plant extract (Regalia)
Salts or esters of phosphorous acid phosphonate
(Aliette)
Streptomyces griseoviridis (Mycostop)biological
stylet oil (JMS)
oil
tebuconazole (Torque)
DMI3–triazole
thiabendazole (Mertect)
benzimidazole
Diseases: General Information
multi-site
—
single-site
single-site
—
single-site
—
—
single-site
—
M 03
40
4
3
NC
14
5
NC
3
NC
low
low to medium
high
medium
none
low-medium
low-medium
none
medium
low
multi-site
P 07
low
—
—
single–site
BM 02
NC
3
low
none
medium
single-site
1
high
Comments
resistance to FRAC 7 has been
documented
resistance risk unknown, but
assumed to be medium to high
cross-resistance to fungicides of
QoI group documented
cross-resistance to fungicides of
QoI group documented
incompatible with most other
pesticides
Resistance is known in several
fungal species, cross-resistance
is present in DMI–group
General Properties of Fungicides (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
thiophanate-methyl (Talaris)
triadimefon (Bayleton)
Trichoderma spp. (RootShield)
trifloxystrobin (Compass O)
triflumizole (TerraGuard)
wettable sulfur
—
NC
1
2
3
4
thiophanate
DMI3-triazole
biological
Qol2
DMI3-imidazole
inorganic
single-site
single-site
—
single-site
single-site
multi-site
1
3
BM 02
11
3
M 02
high
medium
low
high
medium
low
= no information
= not classified
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see
http://frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action group number; for fungicides
with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
Qol
= quinone outside inhibitor
DMI
= demethylation (sterol) inhibitor
EBD
= ethylene bisdithiocarbamate
C
Diseases: General Information
General Properties of Fungicides (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Key Diseases
ARMILLARIA ROOT ROT (OAK ROOT FUNGUS) (11/20)
Armillaria mellea and other species
SYMPTOMS AND SIGNS
Infected field-grown plants can be stunted, show poor growth, have smaller than normal leaves, and can
have other symptoms associated with diseased roots and crowns. Eventually, foliage will wilt, turn
brown, and die. The disease usually results in the complete collapse and death of the plant. Diseased
crowns and main roots will have white to cream-colored fan-shaped mycelial mats, growing underneath
the outer tissues. Dark brown to black stringy mycelial structures (rhizomorphs) are rarely seen on the
root surface.
COMMENTS ON THE DISEASES
Armillaria mellea is a soilborne pathogen that is only found in field soil. The fungus survives on dead roots
left in the ground. Woody crops, planted in areas that were formerly oak woodland, can become infected
many years after infested oaks were removed. The fungus can spread from one plant to another through
the contact of diseased roots with healthy roots. Wet soil conditions resulting from heavy rainfall or excessive irrigations can exacerbate the disease. Under suitable conditions, the mushroom stage of the fungus can emerge from buried diseased roots. The mushroom is large (cap diameter up to 6 inches wide),
has a cap with variable coloration (yellow, tan, honey-colored, brown), and bears typical radiating gills
with white spores.
MANAGEMENT
For field grown ornamental crops the only treatment is fumigation. Before chemical treatment, remove all
infected plants and as many large roots as possible. Complete eradication is rarely achieved, and retreatment may be necessary in localized areas. If the soil is wet or if it has extensive clay layers to the depths
reached by the roots, fumigant treatment may not be successful. Other management options include rotating crops and planting ornamentals that are not hosts to this pathogen.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
SOIL FUMIGATION
A.
Label rates
See label
CHLOROPICRIN*§
COMMENTS: Inject into soil and cover immediately with plastic tarps. Fumigants are a source of volatile organic compounds (VOCs) but are not reactive with other air contaminants that form ozone.
B.
Sequential application of:
(Note: Fumigants such as 1,3-dichloropropene and metam products are a source of volatile organic compounds (VOCs)
but minimally reactive with other air contaminants that form ozone.
CHLOROPICRIN*§/1,3 DICHLOROPROPENE*§
(Pic-Clor60)
300–332 lb (shank)
See label
(Pic-Clor60 EC)
200–300 lb
See label
COMMENTS: Very effective for control of soilborne fungal pathogens and insects. Drip irrigation requires an
emulsifier. For shank fumigation, using higher rates or plastic mulch, especially virtually impermeable film
(VIF), improves weed control. For drip fumigation the use of VIF will improve both nematode and weed control. According to state permit conditions, the maximum application rate of 1,3-dichloropropene is 332
pounds active ingredient per acre. Pic-Clor60: One gallon of weighs 12.1 lb; Pic-Clor60 EC: One gallon of
weighs 11.8 lb.
Key Diseases
Armillaria Root Rot (Oak Root Fungus) (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Following 5–7 days after fumigation:
METAM SODIUM*§
(Vapam HL, Sectagon 42)
37.5–75 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy
affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains
4.26 lb of metam sodium.
. . . or . . .
METAM POTASSIUM*§
(K-Pam HL, Sectagon–K54)
30–45 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy
affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains
5.8 lb of metam potassium.
. . . or . . .
DAZOMET*§
(Basamid)
200 lb
See label
COMMENTS: Powder incorporated into the soil, followed by irrigation or tarping. It decomposes to a gaseous fumigant (methyl isothiocyanate).
*
1
§
‡
Permit required from county agricultural commissioner for purchase or use.
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to
a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than
two consecutive applications before rotating to fungicide with a different mode of action group number.
Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements, which may be lower than maximum label rates.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Armillaria Root Rot (Oak Root Fungus) (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
ASTER YELLOWS (11/20)
Aster yellows phytoplasma
SYMPTOMS AND SIGNS
Symptoms of aster yellows includes yellowing, dwarfed or distorted foliage, and the abnormal production of shoots. Flowers may not develop normally and are often replaced by green leafy structures. Aster
yellows symptoms may closely resemble those caused by viruses.
COMMENTS ON THE DISEASE
Aster yellows is caused by a microscopic organism called a phytoplasma. Phytoplasmas are closely related to bacteria but are somewhat smaller in size and do not have a rigid cell wall.
Initially, the aster yellows phytoplasma was thought to be a virus. Phytoplasmas are vectored by leafhoppers, plant hoppers, and psyllids and invade the phloem of infected plants. The aster yellows phytoplasma is vectored by leafhoppers, in which it can multiply. It has a very wide host range, which includes many ornamentals, food crops, and weeds.
MANAGEMENT
Aster yellows is difficult to control, in part, because of the extensive host range of the pathogen. Over 300
species of food, forage, ornamental, and weed plants are susceptible. While weed management should be
practiced, this will have little effect on aster yellows. Plant pathogen-free plants and use good sanitation.
Remove and destroy infected plants. There are no chemical controls for the aster yellows phytoplasma.
Control of the leafhopper vector could reduce transmission of the phytoplasma.
EXAMPLES OF HOSTS OF ASTER YELLOWS PHYTOPLASMA
Ornamental hosts
alyssum, calceolaria, calendula, China aster, chrysanthemum, cineraria, daisies, delphinium, gladiolus, gloxinia, gypsophila, larkspur, petunia, statice, sweet william,
tagetes, veronica, zinnia, and many others
Key Diseases
Crop plant hosts
Weeds and native plant hosts
buckwheat, carrots, celery, lettuce, onion, California poppy, dandelion, plantain,
parsley, parsnip, potato, safflower, spin- and many others
ach, tomato, and many others
Aster Yellows (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
BACTERIAL LEAF SPOTS, BLIGHTS, CANKERS, AND ROTS
(11/20)
Bacterial blight of chrysanthemum: Dickeya (=Erwinia) chrysanthemi
Bacterial blight of geranium: Xanthomonas axonopodis pv. pelargonii (formerly X. campestris pv. pelargonii)
Bacterial leaf spot of begonia: Xanthomonas axonopodis pv. begoniae (formerly X. campestris pv. begoniae)
Bacterial leaf spot of poinsettia: Curtobacterium flaccumfaciens pv. poinsettiae
Bacterial wilt of carnation: Burkholderia (=Pseudomonas) caryophylli
Black leaf spot of delphinium: Pseudomonas syringae pv. delphinii
SYMPTOMS AND SIGNS
Foliar diseases caused by plant pathogenic bacteria result in a wide range of symptoms that vary greatly
depending on the particular pathogen and the host plant. Leaf spots (also called leaf lesions) are discrete
diseased sections of leaves that initially appear water-soaked, but later turn yellow, brown, or black. Leaf
spots are usually angular in shape and bordered by the veins in the leaf. Leaf petioles can also develop
such spots. Merging of numerous leaf spots results in the infection of large portions of the foliage; such
symptoms are called blights. Rots occur when the bacteria infect fleshy stems, crown, bulbs, corms, and
other parts of plants and cause a soft, watery decay. Infections on twigs and branches can cause cankers,
which are sunken, discolored, and cracked areas in the woody tissue. In some cases, bacteria inside the
diseased tissue will ooze to the surface of the plant and are visible as cream to yellow colored exudates,
collecting outside the plant.
COMMENTS ON THE DISEASES
There are many different kinds of bacterial diseases of flower and nursery crops. In many cases these bacteria are host specific and will only infect one plant species. In other cases, for example with soft rot bacteria, the pathogen is able to infect a larger number of plant hosts. All bacteria in this section can be spread
through infected cuttings and other propagative material, and some of these bacteria may be carried in
seed and irrigation water. Bacteria are dependent on splashing water for their dispersal and for creating a
suitable environment for infection and disease development.
MANAGEMENT
Use pathogen- and disease-free seed, cuttings, transplants, and other propagative materials.
• Implement sanitation measures when dealing with containers, flats, benches, pruning tools, and
other items that come in contact with plants.
• Avoid using overhead sprinkler irrigation.
• Rogue out (remove) diseased cuttings, transplants, and plants.
• Sanitize hands or use disposable gloves when handling diseased plants.
• Prevent injuring bulbs, corms, and other fleshy parts of plants to avoid soft rot problems.
Copper-based fungicides may provide some control but can be phytotoxic to some ornamentals.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. FIXED COPPER
(Kocide 2000)#
Label rates
48
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 01)
COMMENTS: A protectant fungicide. Growth of some plants may be reduced by this material; follow label
directions carefully to reduce the risk of phytotoxicity. Check label for registered use ornamental species list
in California. Not all copper compounds are approved for use in organic production; be sure to check individual products.
1
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. In
Key Diseases
Bacterial Leaf Spots, Blights, Cankers, and Rots (11/20)
18
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
‡
#
California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before
rotating to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no
more than two consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Acceptable for use on organically grown ornamentals. Check with your certifier.
Key Diseases
Bacterial Leaf Spots, Blights, Cankers, and Rots (11/20)
19
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BLACK ROOT ROT (11/20)
Thielaviopsis basicola
SYMPTOMS AND SIGNS
Black root rot is also called Thielaviopsis root rot. Plants are stunted and grow poorly. Infected roots may
initially have small dark brown to black bands where infection has taken place. As the disease progresses,
roots can become badly rotted. Stems below ground may enlarge and develop black, rough, longitudinal
cracks. Characteristic dark brown to black, thick-walled, barrel-shaped chlamydospores form in infected
tissues and may be visible under magnification.
COMMENTS ON THE DISEASE
The fungus has a wide host range: 120 species in 15 families are known to be susceptible. Strains of the
fungus are known that differ in pathogenicity and virulence. Important ornamental hosts include begonia, cyclamen, geranium, gerbera, kalanchoe, pansy, petunia, poinsettia, primula, snapdragon, sweet
pea, verbena, and viola. The disease is favored by wet, cool soil and any condition that weakens plants; it
is most severe from 55° to 61°F, while only a trace of disease develops at 86°F. Alkaline soil favors the disease, which can be prevented at pH 4.8 and greatly reduced at pH 5.5 or below. However, many plants
do not grow well under such acidic conditions.
The fungus is soilborne and capable of prolonged survival in the absence of susceptible plants. Two kinds
of spores are formed:
• barrel-shaped chlamydospores (resting spores) in short chains of three to seven and
• rectangular-shaped endoconidia.
The fungus can be spread in water, soil, by infected plants or vectored by fungus gnats and shore flies.
Some sources of peat are known to harbor Thielaviopsis spores.
MANAGEMENT
Use appropriate sanitation measures to prevent spread of the pathogen via diseased plant material, contaminated soil mixes and containers, and contaminated water runoff. The use of pathogen-free plants,
along with improved sanitation and cultural practices, has reduced the importance of this disease, which
at one time was widespread, especially in poinsettias. The fungus can still be troublesome in field-grown
flowers. The benzimidazole fungicides such as thiophanate-methyl are very active against the fungus and
are used as soil treatments to control it.
To treat container media, steam (at 140°F for 30 minutes), or solarize (double-tent at 160°F for 30 minutes
or 140°F for 1 hour). For flower production in outdoor fields, solarization in warmer climates has been
successful for control of Thielaviopsis in many crops. Solarization and steaming are acceptable for organic
production. For more information, see MANAGEMENT OF SOILBORNE PATHOGENS.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. THIOPHANATE-METHYL
(Talaris 4.5 F)
20 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
COMMENTS: Apply as a drench or heavy spray. Generally applied after sowing. Absorbed by plant parts
exposed to the chemical. Roots may absorb the fungicide (or its breakdown product carbendazim), which
moves in the xylem to transpiring leaves.
B.
TRIFLUMIZOLE
(TerraGuard SC)
Key Diseases
2–8 fl oz/100 gal water
12
Black Root Rot (11/20)
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MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: Apply as a cutting soak or soil drench at 3 to 4 week intervals as needed on potted plants. A
protectant fungicide; use is restricted to enclosed commercial structures such as greenhouses and shade
houses.
C.
1
‡
FLUDIOXONIL
(Medallion WDG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrroles (12)
12
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating
to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more
than two consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can
be safely entered without protective clothing.
Key Diseases
Black Root Rot (11/20)
21
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Cottony Rot (11/20)
Sclerotinia sclerotiorum
SYMPTOMS AND SIGNS
Under high humidity the fungus produces a mass of white cottony mycelia on the soil or plant surface.
Later, large (1/4 to 1 inch long), black sclerotia (hard, dark masses of hyphae) are formed on and inside
infected plant parts. Frequently the sclerotia are found inside hollow stems. Plant tissues killed by the
fungus often take on a bleached appearance. Gray mold (Botrytis cinerea) causes a similar bleaching and
also has black sclerotia, but they are much smaller than those of Sclerotinia. Additionally, Botrytis produces gray mycelium and spores instead of the mass of white, cottony growth that Sclerotinia does.
COMMENTS ON THE DISEASE
Cottony rot, also called Sclerotinia rot or white mold, affects many kinds of plants. It is also a disease of
vegetables, such as beans, carrots, celery, and lettuce. Moisture and high humidity are necessary for development of the disease and this is one reason the disease is found lower in the plant canopy. Infection
can either be soilborne or airborne.
Sclerotinia sclerotiorum does not produce asexual conidia. Sclerotia formed by the fungus undergo a
dormant period that is broken by low temperatures (optimal is 56° to 59°F) and high soil moisture. In fall
and spring, when temperatures are in the optimal range, sclerotia germinate and can infect the plant near
the soil line either directly by producing vegetative strands (hyphae) or by forming apothecia (saucershaped, dime-sized structures on stalks) that produce ascospores (sexual spores). Ascospores are discharged forcibly into the air and are carried by air currents. They do not directly infect healthy tissue, but
if they land on injured tissue in the presence of moisture, infection can occur on any aboveground part.
Flower petals of many plants are susceptible. Foliage may become infected if there is an injury or if the
tissue is senescent. If diseased tissue comes in contact with healthy tissue, the fungus can invade the
healthy tissue.
MANAGEMENT
Protective fungicides, as well as steaming (at 140°F for 30 minutes), solarization (double-tent at 160°F for
30 minutes or 140°F for 1 hour), or fumigation of the growing medium can be helpful. For flower production in open fields, solarization in warmer climates has been successful for control of Sclerotinia diseases
in many crops. Solarization and steaming are acceptable for organic production. In open fields airborne
spores can blow in from outside the field, so soil treatment may be limited in its effectiveness.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a
pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
A. BOSCALID/PYRACLOSTROBIN
(Pageant)
12–18 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
B.
CYPRODINIL/FLUDIOXONIL
(Palladium)
2–4 oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Amino acids and protein synthesis (9) and signal transduction
(12)
C.
IPRODIONE
(Chipco 26019 N/G)
6.5 oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
COMMENTS: Apply as a drench (1–2 pt/sq ft) at seeding or transplanting. Effective against Rhizoctonia damping-off and Sclerotinia. Some iprodione is absorbed by plant parts.
Key Diseases
Cottony Rot (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
D. PCNB
(Terraclor 400)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)
COMMENTS: Inhibits germination of sclerotia when incorporated into top two inches of soil. Insoluble in water.
Must be thoroughly mixed with soil to reach its desired depth of control. Works through vapor action and has
good residual action. Germination of some seeds may be inhibited and small plants may be stunted by this fungicide.
E.
1
‡
THIOPHANATE-METHYL
(Talaris 4.5 F)
20 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
COMMENTS: Apply as a drench or heavy spray (1–2 pt/sq ft) after sowing. Absorbed by plant parts exposed to
the chemical. Roots may absorb the fungicide (or its breakdown product carbendazim), which moves in the xylem to transpiring leaves.
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action.
Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no
more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with
a different mode of action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Cottony Rot (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
CROWN GALL (11/20)
Agrobacterium tumefaciens
SYMPTOMS AND SIGNS
Crown gall is caused by a bacterium that produces galls at the base of the stem, root crown or on other
plant parts. The bacterium infects only through fresh wounds. If infected at a young age, plants may be
stunted and not grow properly.
COMMENTS ON THE DISEASE
A wide variety of both woody and herbaceous plants are susceptible. The disease is most damaging to
trees because the galls are perennial and increase in size with growth of the tree. Galls may occur on
roots, stems, and even leaves. Aerial galls are common on grapes and caneberries. Under moist conditions aerial galls are often seen on chrysanthemum. The disease may have further impact on growers, because regulations prohibit the sale of some plant materials infected with crown gall.
Gall tissue is disorganized growth with an enlarged cambium layer and irregular vascular tissue. Movement of water and nutrients is severely impaired by galls. The early stages of gall formation can be difficult to distinguish from normal callus tissue. Isolation of the pathogenic bacterium is the most common
method of confirming that the bacterium is present. Callus tissue, which is soft and easily wounded, can
be a common site of infection.
The bacterium Agrobacterium tumefaciens is common in many agricultural soils. When the plant is
wounded, the bacterium attaches to an exposed plant cell and transfers a portion of its genetic material,
DNA (deoxyribonucleic acid), into the cell where it is incorporated into the genetic material of the host
cell. The host cell is induced to become a tumor cell and also to produce a unique substance (opine) that
only the crown gall bacterium can readily utilize. Agrobacterium tumefaciens is then able to multiply between cells and in cracks of the gall with somewhat less competition from other microorganisms.
MANAGEMENT
The only useful method of treating soil for crown gall pathogen is with heat. The common soil fumigants
reduce the amount of bacteria but do not result in satisfactory control of the disease. Steam (at 140°F for
30 minutes) or solarize (double-tent at 160°F for 30 minutes or 140°F for 1 hour) the soil. For flower production in open fields, solarization in warmer climates has been successful for control of crown gall.
Steaming and solarization are acceptable for organic production.
Sanitation is very important in a control program, especially where cuttings are produced. Rose propagative material and work areas are often soaked or cleaned with hypochlorite solution to kill any bacteria
that may be present on the surface. Grape propagative material, and perhaps some others, have also been
treated in this manner. In some plants, such as grape, the bacterium may occasionally enter the xylem.
Cuttings taken from such plants may develop crown galls.
Tools and surfaces that contact the propagative material should be cleaned and periodically treated with
a disinfectant.
Monitoring and Treatment Decisions
The K-84 strain of Agrobacterium tumefaciens (formerly A. radiobacter), which is available for use in preventing infection by the crown gall pathogen, is an excellent biological control agent.
Galls on many woody plants can be treated with a mixture of chemicals that are toxic to and kill crown
gall tissue but are safe on uninfected woody tissue. The mixture, which is currently marketed under the
name Gallex, was previously sold as Bacticin. It has been used with success on rose crown galls.
Common name
(Example trade name)
Key Diseases
Amount to use
REI‡
(hours)
Crown Gall (11/20)
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Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. AGROBACTERIUM TUMEFACIENS K-84
(Galltrol)#
Label rates
4
. . . or . . .
AGROBACTERIUM TUMEFACIENS K-1026
(Nogall)
Label rates
4
COMMENTS: Products may list bioagent under former name A. radiobacter. Prevents infection by the crown
gall pathogen if it is applied to fresh wounds. It must be applied as soon as possible after wounding; i.e.,
within 24 hours. It has been used with success on Prunus spp. and Rosa spp.
B.
#
‡
2,4-XYLENOL/META-CRESOL
(Gallex)
Label rates
COMMENTS: For killing of existing galls; apply directly to galls winter through spring.
24
Acceptable for use on organically grown ornamentals.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Crown Gall (11/20)
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DAMPING-OFF (11/20)
Damping-off: Pythium spp., Rhizoctonia solani, and others
SYMPTOMS AND SIGNS
Emerging seedlings rot at or below the soil line and are killed. Some seedlings may be infected before
emergence and therefore not appear above ground. If the problem is caused by Pythium, it usually begins
at the root tips. Damping-off pathogens can also infect planted seeds and cause death of the seed before it
germinates.
COMMENTS ON THE DISEASE
Damping-off is the name given to seedling diseases most often caused by fungi and oomycetes (funguslike organisms). As the name implies, the disease is associated with damp conditions. Some Pythium species are favored by cool, wet conditions, but Rhizoctonia and other Pythium species can cause disease under drier and warmer conditions.
MANAGEMENT
Vigorous seedlings grown from the best seed under ideal light and temperature conditions may survive
in the presence of these fungi, while seedlings low in vigor will succumb under unfavorable conditions.
Damping-off can be minimized by providing good drainage (raised beds, properly graded fields), careful
irrigation, planting when soil and air temperatures are favorable for rapid seedling emergence, proper
depth and spacing of planting, seed treatments, and drenches of soil fungicides. For more information,
see MANAGEMENT OF SOILBORNE PATHOGENS.
For container media, steam (at 140°F for 30 minutes) or solarize (double-tent at 160°F for 30 minutes or
140°F at 1 hour). For flower production in open fields, solarization in warmer climates has been successful for control of damping-off in many crops. Reports of inadequate control of some high temperature
species (e.g., P. aphanidermatum) have been made. Solarization and steaming are acceptable for organic
production.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
SEED TREATMENT
A. STREPTOMYCES GRISEOVIRIDIS
(Mycostop)#
0.08 oz/lb of seed
4
MODE OF ACTION GROUP NAME (NUMBER1): Microbial (BM 02)
COMMENTS: For control of seed rots, root and stem rots, and wilt diseases of ornamental crops caused by
Alternaria, Fusarium, and Phomopsis. Suppresses also Botrytis, Pythium, and Phytophthora. May be used for
both field-grown and greenhouse ornamentals.
SOIL FUNGICIDE – Pythium spp.
A. CYAZOFAMID
(Segway)
1.5–3.0 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone inside inhibitor (21)
COMMENTS: Toxic to aquatic organisms.
B.
C.
FENAMIDONE
(Fenstop)
7–14 fl oz/50–100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Toxic to aquatic organisms.
FLUOPICOLIDE
(Adorn)
1–4 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Benzamides (43)
Key Diseases
12
12
12
Damping-off (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
COMMENTS: Toxic to aquatic organisms.
D. MEFENOXAM
(Subdue Maxx)
Label rates
48
MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)
COMMENTS: Applied at planting as a drench and periodically thereafter as needed. Available also in a
granular formulation to use before planting. It is water-soluble and readily leached from soil. It is absorbed
primarily through roots and is translocated in the plant through the xylem. Use of this material over a period of time may lead to resistance.
SOIL FUNGICIDE – Rhizoctonia solani
A. FLUDIOXONIL
(Medallion WDG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrroles (12)
B.
C.
12
IPRODIONE
(Chipco 26019 N/G)
6.5 oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
COMMENTS: Apply as a drench at seeding at the rate of 1–2 pt/sq ft
12
FLUTOLANIL
(Prostar 70 WG)
3–6 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Succinate-dehydrogenase inhibitor (7)
D. PCNB
(Terraclor 400)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)
COMMENTS: Insoluble in water. Must be thoroughly mixed into the top 2 inches of soil to reach its desired
depth of control. It works through vapor action and has good residual action. Germination of some seeds
may be inhibited, and small plants may be stunted by this fungicide.
E.
THIOPHANATE-METHYL
(Talaris 4.5 F)
20 fl oz/100 gal for 800 sq ft bench area
12
MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
COMMENTS: Generally applied after sowing, as a drench or heavy spray. Thiophanate-methyl is absorbed
by plant parts exposed to the chemical. Roots may absorb the fungicide (or its breakdown product carbendazim), which moves in the xylem to transpiring leaves.
F.
TRIFLUMIZOLE
(TerraGuard SC)
4–8 fl oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: For use in enclosed commercial structures only; less effective against Rhizoctonia than other
materials. Apply as a soil drench at 3 to 4 week intervals as needed.
SOIL FUNGICIDE – Pythium spp. and Rhizoctonia solani
A. BOSCALID/PYRACLOSTROBIN
(Pageant)
12–18 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
B.
TRICHODERMA spp.
(RootShield)#
Label rates
NA
MODE OF ACTION GROUP NAME (NUMBER1): microbial (BM 02)
COMMENTS: Formulated as a seed protectant, a soil drench, and as granules. This biological fungicide may
provide some protection against both Pythium and Rhizoctonia.
1
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating
to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more
than two consecutive applications before rotating to fungicide with a different mode of action group number.
Acceptable for use on organically grown ornamentals.
#
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can
be safely entered without protective clothing.
Key Diseases
Damping-off (11/20)
27
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
N
A
Not applicable.
Key Diseases
Damping-off (11/20)
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DOWNY MILDEW (11/20)
Downy Mildew: Bremia sp., Peronospora spp., Plasmopara spp.
SYMPTOMS AND SIGNS
The name downy mildew is somewhat descriptive of the fluffy appearance of the white, lavender, or purple sporulation that occurs usually on the undersides of diseased leaves. Downy mildew leaf lesions are
often angular in shape and delimited by veins. Paleyellow, purple, or necrotic areas often are visible from
the upper side of the leaf. Extensive disease can result in the death of large portions of the leaves.
In some plants, when young shoots are infected, the fungus may become systemic and the resultant
growth is stunted, malformed, and discolored.
COMMENTS ON THE DISEASE
In contrast to powdery mildews, the downy mildews require very wet or humid conditions to flourish.
Water is required for infection, and humidity above 90% is needed for sporulation. Growth of the pathogens is favored by cool temperatures.
Downy mildew spores are usually short-lived, although they may survive several days under cool, moist
conditions. They are airborne, and when they land on a susceptible plant with free water present, germination and infection generally occur within 8 to 12 hours. Some downy mildews also produce a sexual
spore (oospore) that can survive dry conditions. This enables the pathogen to survive in the absence of a
host. Downy mildews are favored by moist and cool conditions (40° to 60°F).
MANAGEMENT
Use varieties resistant to downy mildew. Avoid sprinkler irrigation and reduce relative humidity in
greenhouses. Fungicide treatment of susceptible varieties is needed when the disease occurs on transplants or early in crop development in the field; repeated applications may be required to protect new
growth. Treatment during early flowering is required on some seed crops.
Organically Acceptable Methods
Resistant varieties and some copper sprays are suitable for organically grown crops.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. AMETOCTRADIN/DIMETHOMORPH
(Orvego)
11–14 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Mitochondrial respiration inhibitor (45) and cell wall synthesis inhibitor (40)
B.
BOSCALID/PYRACLOSTROBIN
(Pageant)
12–18 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
C.
FIXED COPPER
(Kocide 2000)#
Label rates
48
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 01)
COMMENTS: A protectant fungicide. Growth of some plants may be reduced by this material; follow label
directions carefully to reduce the risk of phytotoxicity. Not all copper compounds are approved for use in organic production; be sure to check individual products.
D. CYAZOFAMID
(Segway)
2.1–3.5 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Ubiquinone reductase, Qi site (21)
COMMENTS: Toxic to aquatic organisms.
Key Diseases
12
Downy Mildew (11/20)
29
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
E.
F.
FENAMIDONE
(Fenstop)
7–14 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Toxic to aquatic organisms.
FLUOPICOLIDE
(Adorn)
1–4 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Benzamides (43)
COMMENTS: Toxic to aquatic organisms.
12
12
G. SALTS OR ESTERS OF PHOSPHOROUS ACID
(Aliette WDG)
2.5–5 lb/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Phosphonate (P 07)
COMMENTS: For control of downy mildew on roses. Spray to wet using no more than 400 gal/acre.
H. MANCOZEB
(Dithane 75DF)
1–1.5 lb/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 03)
COMMENTS: A protectant fungicide. Thorough coverage is important for control.
I.
J.
K.
1
#
‡
MANDIPROPAMID
(Micora)
4–8 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Carboxylic acid amides (40)
MEFENOXAM
(Subdue Maxx)
0.5–1.0 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)
COMMENTS: Tank-mix with a non-Group 4 fungicide labeled for downy mildew.
REYNOUTRIA SACHALINENSIS#
(Regalia CG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): anthraquinone elicitor (P 05)
24
4
48
4
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California,
make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a
fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two
consecutive applications before rotating to fungicide with a different mode of action group number.
Acceptable for use on organically grown ornamentals.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Downy Mildew (11/20)
30
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
FUNGAL LEAF SPOTS, BLIGHTS, AND CANKERS (11/20)
Leaf spot of aster: Stemphylium callistephi
Ovulinia petal blight of azalea: Ovulinia azaleae
Alternaria blight of carnation: Alternaria saponariae (formerly A. dianthi)
Leaf blotch of peony: Cladosporium paeoniae
Black spot of rose: Diplocarpon rosae
Cercospora leaf spot of statice: Cercospora insulana
SYMPTOMS AND SIGNS
Foliar diseases caused by plant pathogenic fungi result in a wide range of symptoms that vary greatly depending on the particular pathogen and the host plant. Leaf spots (also called leaf lesions) are discrete,
diseased sections of leaves that initially may be dull green or yellow in color, but later turn brown, black,
or display another abnormal color. Leaf spot shapes also vary greatly, but usually are oval, oblong, or
round. Leaf petioles can also develop such spots. The occurrence and merging of numerous leaf spots results in the infection of large portions of the foliage; such symptoms are called blights. Infections on twigs
and branches can cause cankers, which are sunken, discolored, and cracked areas in the woody tissue. In
many cases, the mycelium and fruiting structures of the pathogenic fungi will grow on top of the diseased leaf spot, blight, and canker areas.
COMMENTS ON THE DISEASE
There are many different kinds of foliar fungal diseases of flower and nursery crops. In many cases these
fungi are host specific and will only infect one plant species. Most of these organisms produce spores that
are spread by wind currents and splashing water from rain or sprinklers. Moist, humid conditions are
needed for infection and disease development. Some of these fungi are carried in the seed; all can be carried in infected cuttings and other propagative material.
MANAGEMENT
Use pathogen- and disease-free seed, cuttings, transplants, and other propagative materials. Implement
sanitation measures when dealing with containers, flats, benches, pruning tools, and other items that
come in contact with plants. Avoid using overhead sprinkler irrigation. Rogue out diseased cuttings,
transplants, and plants. Sanitize hands or gloves after handling diseased plants. Fungicides provide some
control.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. Strobilurins such as AZOXYSTROBIN, PYRACLOSTROBIN, TRIFLOXYSTROBIN and FLUOXASTROBIN
(Heritage, Compass O 50WDG)
Label rates
See label
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
1
‡
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California,
make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a
fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two
consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Fungal Leaf Spots, Blights, and Cankers (11/20)
31
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
FUSARIUM WILT (11/20)
Fusarium oxysporum
SYMPTOMS AND SIGNS
Symptoms include yellowing, stunting, and death of seedlings and yellowing and stunting of older
plants. Infected plants wilt readily, lower leaves yellow and dry, the xylem tissues turn brown, and the
plant may die. In the early stages of disease, the roots are not rotted. In many plants such as carnation
and gladiolus, the symptoms may be one-sided at first.
COMMENTS ON THE DISEASE
The fungi that cause Fusarium wilt diseases are composed of a group of host-specific forms (forma specialis) abbreviated f. sp. For example, the fungus that causes wilt of carnations is Fusarium oxysporum f. sp.
dianthi and infects only carnations and closely related plants. Generally, the f. sp. relates to the host; e.g.,
callistephi (China aster), pisi (pea), cyclaminis (cyclamen), etc.
Within the specialized forms are races of the fungus that are characterized by specialization on different
cultivars of a host species. Cultivar A may be susceptible to race 1 and resistant to race 2, while cultivar B
may be susceptible to both race 1 and race 2. This complicates the grower’s task of selecting which cultivars to grow, as well as making it more difficult to select a breeding strategy for developing resistant cultivars.
There are many saprophytic forms of F. oxysporum, and recovery of this fungus from diseased plant material does not mean that the isolate is a wilt pathogen. For example, it is quite common to recover a saprophytic F. oxysporum from the roots of chrysanthemum plants killed by Pythium spp. or other pathogens.
There are also strains of F. oxysporum that cause root rots but are not wilt pathogens.
The fungus can produce several different kinds of spores. Chlamydospores have thick walls and are resistant to drying and adverse conditions, enabling the fungus to survive for extended periods (years) in
the soil. Conidia are thin–walled spores that can be either long and multi-celled (macroconidia) or short
and only one- or two-celled (microconidia). Conidia are produced in a sporodochium, which is a mass of
conidiophores (conidia-bearing stalks) growing tightly together. However, sporodochia are rarely seen in
Fusarium wilt diseases. Conidia are spread in contaminated soil, by splashing water, and on contaminated tools and hands. Conidia are generally not airborne, but the fungus can become airborne on bits of
infected plant debris or in dust.
In the presence of roots, chlamydospores or conidia germinate and penetrate susceptible plants. The fungus enters the xylem and grows upward, plugging the tissue and reducing the movement of water. Toxins are produced that cause the foliage to turn yellow.
Fusarium wilts are favored by high air and soil temperatures (75° to 86°F). Disease may not occur at low
soil temperatures (below 68°F), or an infected plant may remain symptomless at lower temperatures. The
fungus can be spread with infected cuttings or other forms of vegetative propagation taken from healthy
appearing but infected plants.
MANAGEMENT
If seed is taken from infected plants, the seed itself is usually healthy, but the seed coat often becomes
contaminated by microscopic pieces of infected tissue and by spores. Many important Fusarium wilt diseases are spread in this manner.
• Treat seed with a fungicide or heat to destroy the fungus on the seed and to protect the emerging
seedlings from infection.
• Dip bulbs and corms in fungicide or hot water (or both) to reduce Fusarium.
Presence of pathogenic Fusarium in the soil can be reduced by heat treatments and chemical fumigation.
These treatments are more effective in controlling the fungus in annual plantings than in perennial plantings. In general, however, Fusarium wilt diseases are best controlled by using resistant or tolerant cultivars, not by using soil applied fungicides. Liming soils and using nitrate nitrogen fertilizer have been effective for management of F. oxysporum on chrysanthemum, aster, gladiolus, cucumber, tomato, and
Key Diseases
Fusarium Wilt (11/20)
32
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
watermelon. In greenhouse production use steam from boilers and apply to raised field beds or raised
benches to control soil borne diseases such as Fusarium wilt. In field production use long rotations or try
to follow a fumigated crop like strawberry.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
SOIL FUMIGATION
A. CHLOROPICRIN*
Label rates
See label
COMMENTS: Inject into soil and cover immediately with plastic tarps. Fumigants are a source of volatile organic compounds (VOCs) but are not reactive with other air contaminants that form ozone. Fumigate only as a
last resort when other management strategies have not been successful or are not available.
B.
Sequential application of:
(Note: Fumigants such as 1,3-dichloropropene and metam products are a source of volatile organic compounds (VOCs) but
minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management
strategies have not been successful or are not available.)
CHLOROPICRIN*/1,3 DICHLOROPROPENE*
(Pic-Clor60)
300–332 lb (shank)
See label
(Pic-Clor60 EC)
200–300 lb
See label
COMMENTS: Very effective for control of soilborne fungal pathogens and insects. Drip irrigation requires an
emulsifier. For shank fumigation, using higher rates or plastic mulch, especially virtually impermeable film
(VIF), improves weed control. For drip fumigation the use of VIF will improve both nematode and weed control. According to state permit conditions, the maximum application rate of 1,3-dichloropropene is 332 pounds
active ingredient per acre. Pic-Clor60: One gallon of weighs 12.1 lb; Pic-Clor60 EC: One gallon of weighs 11.8
lb.
Following 5 to 7 days after fumigation:
METAM SODIUM*
(Vapam HL, Sectagon 42)
37.5–75 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy
affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains
4.26 lb of metam sodium.
. . . or . . .
METAM POTASSIUM*
(K-Pam HL, Sectagon–K54)
30–45 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy
affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains 5.8
lb of metam potassium.
. . . or . . .
DAZOMET*
(Basamid)
200 lb
See label
COMMENTS: Powder incorporated into the soil, followed by irrigation or tarping. It decomposes to a gaseous
fumigant (methyl isothiocyanate).
*
#
§
Permit required from county agricultural commissioner for purchase or use.
Acceptable for use on organically grown ornamentals.
Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements,
which may be lower than maximum label rates.
Key Diseases
Fusarium Wilt (11/20)
33
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Fusarium Wilt (11/20)
34
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
GRAY MOLD (11/20)
Botrytis cinerea
SYMPTOMS AND SIGNS
Gray mold is one of the most destructive plant pathogens and attacks a wide variety of plants. Flower
petals and ripening fruits and vegetables are particularly susceptible to infection, but leaves and stem
tissues may also get infected. Young seedlings of several crops can be killed if infected with gray mold. In
high relative humidity, the fungus may sporulate on infected tissues and produce masses of characteristic
gray or brownish spores that become airborne, which is primarily how the fungus is disseminated.
Spores must have moisture to germinate and infect.
COMMENTS ON THE DISEASE
Botrytis does not invade healthy green tissue such as leaves and stems unless (a) an injured or dead area
is present, or (b) it grows directly from a food base such as a fallen petal or leaf. The fungus will first colonize the food base and then attack healthy green tissues. However, flower petal tissue differs significantly
from leaf and stem tissue, and Botrytis can directly invade petals of African violet, aster, begonia, carnation, chrysanthemum, cyclamen, cymbidium, gerbera, geranium, gladiolus, hydrangea, marigold, orchid,
petunia, poinsettia, primrose, ranunculus, rose, snapdragon, zinnia, and others.
Although the fungus is capable of growth within a wide range of temperatures from about 28° to 90°F,
growth is very slow at the extremes. Optimum temperature range for growth is 70° to 77°F. The fungus,
which is more active below 70° than it is above 77°F, is particularly troublesome under conditions of
moderate temperature and high humidity.
MANAGEMENT
Refrigeration at temperatures near 32°F will retard but not completely stop the development of gray
mold; when infected tissue is warmed, decay can proceed rapidly.
Moisture often is more of a limiting factor than temperature. Free moisture is necessary for germination
of Botrytis spores. Moisture is also necessary for growth within plant tissues, and low humidity may result in arrested growth of the fungus. However, growth can resume when moisture again becomes available.
Gray mold is most severe during times of the year when the humidity is high. In California, this is usually in the late fall and winter months, when rainfall is common. The worst time for disease development
is from September to December, because there is an abundant amount of herbaceous vegetative material
(crop refuse and dying summer plants) available for fungal colonization and, as a consequence, many
spores are present in the air and on plant parts.
Cultural Control
Botrytis cinerea produces innumerable asexual spores (conidia) that are moved by air currents. Because
spores may readily develop in decaying vegetation and old flowers, elimination or reduction of sources
of the spores is an important part of any control program.
• Remove old flowers before they become infected and function as spore sources. The fungus can
develop and sporulate at low temperatures, so do not overlook old flowers and foliage in refrigerators.
• Avoid condensation of water on susceptible plant parts, as free moisture is necessary for germination and infection
• Avoid overhead watering during blooming. If this is the only method of irrigation available, irrigate early in the day so that the foliage can dry as rapidly as possible.
• Maximize the period between irrigations to further enhance drying of foliage and flowers.
• Increase plant spacing to increase ventilation and minimize leaf wetness. This can help reduce
both disease incidence and severity.
Key Diseases
Gray Mold (11/20)
35
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Chemical Control
Numerous fungicides are effective against B. cinerea but not all of them can be used on all crops. Some
products can damage plants. To avoid damage and the development of fungal strains that are resistant to
fungicides, growers should alternate different fungicides. The fungicides are preventives and must be applied before infection. In some crops, such as chrysanthemum, the lower foliage of crowded plants becomes infected and acts as a source of spores that then infect the flowers. In these crops, it is important to
apply fungicides at an early stage when the lower foliage can be adequately covered by the chemical.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
A. AZOXYSTROBIN
4–8 oz/100 gal water
4
(Heritage)
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Apply as a broadcast or banded spray targeted at the foliage or crown of the plant. A locally systemic fungicide.
B.
BOSCALID/PYRACLOSTROBIN
12–18 oz/100 gal
12
(Pageant)
1
MODE OF ACTION GROUP NAME (NUMBER ): Carboximide (7) and quinone outside inhibitor (11)
C.
CHLOROTHALONIL
1.375 pt/100 gal water
12
(Daconil WeatherStik)
1
MODE OF ACTION GROUP NAME (NUMBER ): Multi-site contact (M 05)
COMMENTS: Do not apply to either green or variegated Pittosporum or to Schefflera. Effective for the control
of Botrytis spp., Alternaria spp., Rhizoctonia spp., as well as other leaf-spotting fungi on many ornamentals.
D. CYPRODINIL/FLUDIOXONIL
12
(Palladium)
4–6 oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Amino acids and protein synthesis (9) and signal transduction (12)
E.
F.
FENHEXAMID
0.75-1.5 lb/100 gal water
(Decree 50 WDG)
MODE OF ACTION GROUP NAME (NUMBER1): Hydroxyanilide (17)
COMMENTS: Apply as a spray; very effective and can be applied after infection.
FLUDIOXONIL
Label rates
(Medallion WDG)
MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrroles (12)
G. FLUOXASTROBIN
4–8 fl oz/100 gal
(Disarm 480 SC)
1
MODE OF ACTION GROUP NAME (NUMBER ): Quinone outside inhibitor (11)
COMMENTS: Preventative application.
H. IPRODIONE
6.5 oz/100 gal water
(Chipco 26019 N/G)
MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
Key Diseases
12
12
12
12
Gray Mold (11/20)
36
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
COMMENTS: Apply as a drench (1–2 pt/sq ft) at seeding or transplanting. Some resistance has been reported
with this material. Effective against Rhizoctonia damping-off, Sclerotinia, and gray mold. Some iprodione is
absorbed by plant parts.
I.
MANCOZEB
1–1.5 lb/100 gal water
24
(Dithane 75DF)
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 03)
COMMENTS: Protects against leaf spots, Botrytis, rusts, and blight. Not systemic so thorough coverage is important for control.
J.
THIOPHANATE-METHYL
20 fl oz/100 gal water
12
(Talaris 4.5 F)
1
MODE OF ACTION GROUP NAME (NUMBER ): Methyl benzimidazole (1)
COMMENTS: Apply as a drench or heavy spray (1–2 pt/sq ft) after sowing. Some resistance has been reported
with this material. Thiophanate-methyl is absorbed by plant parts exposed to the chemical. Roots may absorb
the fungicide (or its breakdown product carbendazim), which moves in the xylem to transpiring leaves.
K.
DICLORAN
(Botran 75-W)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): AH-fungicides (14)
1
‡
12
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California,
make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a
fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two
consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Gray Mold (11/20)
37
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
PHYTOPHTHORA ROOT AND CROWN ROTS (11/20)
Phytophthora spp.
SYMPTOMS AND SIGNS
Many, if not most, Phytophthora species can infect roots in the same manner as Pythium species. In addition, Phytophthora species infect crowns, stems, and larger roots, particularly in woody plants. Infection of
the roots, crowns, and lower stems result in dark, discolored tissues. Tissues of diseased roots become
soft and mushy and outer layers of the root may slough off. Plants with infected roots and crowns become stunted, are low in vigor, wilt, and appear as if they were water stressed. Foliage turns yellow,
leaves fall off, and the plant may wilt and die.
Aerial plant parts, including branches and shoots, can also be infected by some species of Phytophthora
under wet conditions if infested soil, water, or airborne spores contact these aboveground parts.
COMMENTS ON THE DISEASE
The pathogens that cause Phytophthora root and crown rots are related to Pythium species. Pythium and
Phytophthora are sometimes collectively referred to as the water molds and are grouped in the family
Pythiaceae. Root and crown rots are most common under wet or over-irrigated soil conditions. Ideal soil
conditions for the growth of Phytophthora are wet soils with temperatures in the range of 59° to 74°F. Like
Pythium spp., these fungi can be spread by fungus gnats and shore flies.
Phytophthora species have the same type of reproductive structures as Pythium species (i.e., oospores, sporangia, chlamydospores, and zoospores). Sporangia of some Phytophthora species (e.g., P. infestans and P.
nicotiana) are airborne and aerial plant parts are the principal infection sites. ELISA test kits are available
for detecting Phytophthora.
MANAGEMENT
Emphasis in control of Phytophthora diseases is placed on providing good drainage and water management. In addition, because aerial parts often are infected, propagative material can be a source of infection. Deep planting where soil covers the base of the stem encourages infection by Phytophthora. The same
fungicides active against Pythium species also have activity against Phytophthora species. Copper-containing fungicides are also useful in protecting aerial parts of plants from infection by Phytophthora spp.
Both Pythium and Phytophthora species can be introduced to planting areas via contaminated surface water and soil. Aerial infections by Phytophthora species of a number of plants have been observed where
overhead irrigation with water from streams is practiced or where untreated, recirculated water is used.
For more information, see MANAGEMENT OF SOILBORNE PATHOGENS.
Steam (at 140°F for 30 minutes), solarize (double-tent at 160°F for 30 minutes or 140°F for 1 hour), or
chemically treat growing medium. Sanitation is important because Phytophthora spp. can survive in dust,
planting medium, or soil particles on greenhouse floors and in flats and pots. Remove and discard diseased plants. Use of properly composted pine bark as 20% of potting mix is reported to provide some
control of Pythium and Phytophthora root rots. For flower production in open fields with warmer climates,
solarization has successfully controlled most Phytophthora species in many crops. Care must be taken not
to re-infest treated soil via contaminated plants, soil, media, or water. Solarization, steaming, and composting are acceptable for organic production.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
A. AMETOCTRADIN/DIMETHOMORPH
(Orvego)
Key Diseases
11–14 fl oz/50–100 gal water
12
Phytophthora Root and Crown Rots (11/20)
38
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
MODE OF ACTION GROUP NAME (NUMBER1): Mitochondrial respiration inhibitor (45) and cell wall synthesis inhibitor (40)
B.
C.
CYAZOFAMID
(Segway)
3.0–6.0 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Ubiquinone reductase, Qi site (21)
COMMENTS: Toxic to aquatic organisms.
FENAMIDONE
(Fenstop)
7–14 fl oz/50–100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Toxic to aquatic organisms.
D. FLUOPICOLIDE
(Adorn)
1–4 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Benzamides (43)
COMMENTS: Toxic to aquatic organisms.
E.
F.
FLUOXASTROBIN
(Disarm 480 SC)
0.15–0.60 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
12
12
12
12
SALTS OR ESTERS OF PHOSPHOROUS ACID
(Aliette WDG)
2.5–5 lb/100 gal water for foliar application
12
MODE OF ACTION GROUP NAME (NUMBER1): Phosphonate (P 07)
COMMENTS: Foliar spray is more effective than the soil drench. When applied as a foliar spray it is absorbed
by foliage and moves into roots.
G. MANDIPROPAMID
(Micora)
4–8 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Carboxylic acid amides (40)
4
H. MEFENOXAM
(Subdue Maxx)
0.5–1.0 fl oz/100 gal water
48
MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)
COMMENTS: Applied at planting as a drench and periodically thereafter as needed. Available also in a granular formulation to use before planting. It is water-soluble and readily leached from soil. It is absorbed primarily
through roots and is translocated in the plant through the xylem. Use of this material over a period of time
may lead to resistance.
I.
1
#
‡
REYNOUTRIA SACHALINENSIS
(Regalia CG)#
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): anthraquinone elicitor (P 05)
4
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action.
Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make
no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide
with a different mode of action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
Acceptable for use on organically grown ornamentals.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Phytophthora Root and Crown Rots (11/20)
39
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
POWDERY MILDEW (11/20)
Powdery mildew: Erysiphe spp., Golovinomyces spp., Leveillula (=Oidiopsis) taurica, Oidium sp., Podosphaera
spp.
SYMPTOMS AND SIGNS
Powdery mildew is the name given to diseases resulting from infection by fungi that produce a white to
gray, powdery growth on the surfaces of leaves and sometimes other plant parts. Leaves may yellow,
then brown and die. Infected tissues may be distorted and misshapen.
COMMENTS ON THE DISEASE
There are many kinds of powdery mildew fungi, and most are highly specialized. For example, the powdery mildew that infects squash plants will infect some other plants in the cucurbit family but will not
infect roses, and the powdery mildew from roses will not attack zinnias (and vice versa), although the
fungus that infects zinnias also infects many other members of the composite family. Powdery mildew
fungi are obligate parasites; that is, they can grow only on living plant tissue. When the mildew-infected
plant part dies, so does the mildew unless chasmothecia (spherical, resting stages of the fungus) are
formed.
Most powdery mildew fungi grow over the surface of the leaf, sending short food-absorbing projections
(haustoria) into the epidermal cells. The fungi produce masses of spores (conidia), which become airborne and spread to other plants. Powdery mildew spores require no external moisture for germination,
while most other fungi require free water in the form of dew, guttation, rain, or water from overhead irrigation for germination and infection. Conidia of powdery mildew (except those that infect grasses) die in
water. Spores may be dispersed, however, by splashing water.
The fungus survives in the absence of susceptible host tissues by forming a sexual stage (chasmothecia)
resistant to drying and other adverse environmental conditions. With many perennial plants, such as
rose, the fungus survives as mycelium in dormant buds or actively on plant tissues. Powdery mildews
are particularly severe in semiarid regions, such as most of California, and are less troublesome in high
rainfall areas.
Powdery mildews are favored by warm days and cool nights and moderate temperatures (68° to 86°F). At
leaf temperatures above 90°F, some mildew spores and colonies are killed. Shade or low light intensities
as well as high relative humidity (greater than 95%) favor powdery mildew fungi. Greenhouse conditions
are often ideal for development of the disease.
MANAGEMENT
The best control is through the use of resistant cultivars. However, little attention has been paid to the development of resistant cultivars in flower and nursery crops. Increased air movement around the plants
in the greenhouse tends to reduce infection potential of mildews. Plants that have been treated with antitranspirants are less likely to develop powdery mildew infections
Monitoring and Treatment Decisions
In general, there are two types of fungicidal control: eradication of existing infections and protection of
healthy tissues. In practice, some products provide both protection and eradication, especially when good
wetting of the plant is achieved. To achieve good wetting, some of these products may require the addition of surfactants.
The fungus has developed resistance to some of these fungicides. Rotate the different fungicides to help
slow down the development of fungicide resistance within fungal strains.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
Key Diseases
Powdery Mildew (11/20)
40
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
PROTECTANTS (Must be applied to healthy tissues before infection takes place)
A. TEBUCONAZOLE
(Torque)
4–10 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant.
B.
CYPRODINIL/FLUDIOXONIL
(Palladium)
4–6 oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Amino acids and protein synthesis (9) and signal transduction (12)
C.
BOSCALID/PYRACLOSTROBIN
(Pageant)
6–12 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
D. FLUOXASTROBIN
(Disarm 480 SC)
1–4 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
12
E.
WETTABLE SULFUR#
3 lb/100 gal water
24
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 02)
COMMENTS: Use a wetting agent. Effectiveness of sulfur increases with increasing temperature, but the likelihood of plant injury increases also. Plant damage may result if sulfur is applied at temperatures exceeding
90°F. Some plants, such as melons, are sensitive to sulfur. Sulfur can be applied as a dust or as a spray. Repeated applications are generally necessary to protect new growth and also to renew deposits removed by rain
or irrigation.
F.
MYCLOBUTANIL
(Rally 40WSP)
3 oz/50 gal water
24
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant of rusts or powdery mildew on carnations, crape myrtle, gerbera, roses, and snapdragons.
G. AZOXYSTROBIN
(Heritage)
1–4 oz/100 gal water
4
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Acts as a protectant but has some eradicant properties. A locally systemic fungicide that is an
eradicant and protectant against some powdery mildews.
H. TRIADIMEFON
(Bayleton Flo)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): DMI (Group 3)1 triazole fungicide
COMMENTS: A long-lasting systemic fungicide that provides for general control of some powdery mildews,
some rusts, and leaf blight and spots in greenhouses and commercial nurseries.
I.
THIOPHANATE-METHYL
(Talaris 4.5 F)
10–20 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
Key Diseases
12
Powdery Mildew (11/20)
41
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
COMMENTS: Not as effective against powdery mildew as other materials. Thiophanate-methyl is absorbed by
plant parts exposed to the chemical. Roots may absorb the fungicide (or its breakdown product carbendazim),
which moves in the xylem to transpiring leaves.
J.
K.
L.
PROPICONAZOLE
(Banner Maxx II)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A preventive fungicide.
REYNOUTRIA SACHALINENSIS#
(Regalia CG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Anthraquinone elicitor (P 05)
12
4
POTASSIUM BICARBONATE
(Kaligreen)#
1–3 lb/100 gal water/acre
4
MODE OF ACTION GROUP NAME (NUMBER1): Inorganic salt (NC)
COMMENTS: Primarily a protectant but it eradicates some existing infections with thorough coverage. Apply
at first signs of infection. Thorough coverage is essential for good protection. Labeled for use on roses, field
ornamentals, and greenhouse ornamentals.
ERADICANTS
A. LIME SULFUR 28%
(Rex lime sulfur solution)#
0.5 gal/100 gal water
48
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 02)1
COMMENTS: Primarily an eradicant but has some protectant properties. Plant damage may result if applied
when temperatures exceed 80°F. Not as effective against powdery mildew as other materials. Not for use in
greenhouses.
B.
NEEM OIL
(Triact 70)#
Label rates
4
MODE OF ACTION GROUP NAME (NUMBER1): (NC)
COMMENTS: A broad-spectrum botanical pesticide derived from the neem tree that is effective against various fungal diseases including black spot on roses, powdery mildew, downy mildew, anthracnose, and leaf
spot. Registered for landscape and nursery ornamentals; oils work best as eradicants but also have some protectant activity. When using as a protectant, apply on a 14-day schedule; as an eradicant, apply on a 7-day
schedule. Do not repeat oil applications frequently as multiple applications may burn leaves and flowers.
Never apply any oil within 2 weeks of a sulfur spray or plants may be injured.
C.
PIPERALIN
(Pipron)
4–8 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Amine (morpholine) (5)1
COMMENTS: Requires thorough coverage. For use in greenhouses only. A foliar spray that eradicates powdery mildew on rose, lilac, dahlia, phlox, zinnia, chrysanthemum, and catalpa.
D. STYLET OIL
(Organic JMS Stylet Oil)#
1 oz/gal water
4
MODE OF ACTION GROUP NAME (NUMBER1): (NC)
COMMENTS: A good eradicant for mild to moderate powdery mildew infections; oils work best as eradicants
but also have some protectant activity. Registered for use on chrysanthemum, dieffenbachia, philodendron,
poinsettia, and roses. May be phytotoxic, especially on greenhouse roses. Do not repeat oil applications frequently as multiple applications may burn leaves and flowers. Do not apply to plants suffering from heat or
moisture stress. Never apply any oil within 2 weeks of a sulfur spray or plants may be injured.
Key Diseases
Powdery Mildew (11/20)
42
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
E.
TEBUCONAZOLE
(Torque)
4–10 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant.
1
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action.
Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make
no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
#
Acceptable for use on organically grown ornamentals.
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Powdery Mildew (11/20)
43
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
PYTHIUM ROOT ROT (11/20)
Pythium spp.
SYMPTOMS AND SIGNS
Pythium attacks juvenile tissues such as the root tip and newly germinated seedlings. After gaining entrance to the root the fungus may cause a rapid, brown to black rot of the entire primary root and may
even move up into the stem tissue. As the soil dries, new roots may be produced and the plant may recover or never show symptoms of disease. Under wet conditions brought about by poor soil drainage or
excess irrigation, more and more roots are killed and the plant may wilt, stop growing, or even collapse
and die. Bulbs of susceptible plants turn brown to black, gradually desiccate, and form a hard mummy.
COMMENTS ON THE DISEASE
The pathogens that are responsible for Pythium root rot, also known as water molds, are present in practically all cultivated soils and attack plant roots under wet conditions. These fungi can be spread by fungus gnats and shore flies and end up contaminating potting mixes in containers. There are many species
of Pythium; a few of these species are beneficial in that they compete with or parasitize the pathogenic
species. Of the many pathogenic species, some have limited host ranges while others, such as Pythium ultimum, have very wide host ranges.
Some Pythium species, such as P. aphanidermatum, are pathogens only at high temperatures (above 77°F),
and some are active only at low soil temperatures. Soil moisture conditions of 70% or higher of available
water capacity are conducive to infection by Pythium. It is likely that soil from a field contains several
pathogenic Pythium species.
Pythium species form several types of spores, but not all species form all types. Zoospores, which are produced in sporangia, are motile in water. Oospores, which result from a sexual process, usually undergo a
period of dormancy and can withstand long periods of drying. Some species also form chlamydospores,
which are asexual and have thick cell walls. These structures can serve as survival or overwintering structures. Sporangia and zoospores in general do not survive in air or dry soil for long periods of time.
MANAGEMENT
In the control of Pythium diseases, emphasis is placed on providing good drainage and water management.
• Steam (at 140°F for 30 minutes), solarize (double-tent at 160°F for 30 minutes or 140°F at 1 hour),
or chemically treat the growing medium.
• Sanitize well because Pythium spp. can survive in dust, planting medium, or soil particles on
greenhouse floors and in flats and pots.
• Remove and discard diseased plants.
• Use of properly composted pine bark as 20% of a potting mixture is reported to provide some
control of Pythium and Phytophthora root rots. Additionally, the mycoparasite Gliocladium virens
is used as a Pythium biocontrol agent.
For flower production in outside fields, solarization has been successful for control of damping–off in
many crops that are grown in warmer climates. There are reports of inadequate control of some high temperature species (e.g. P. aphanidermatum). Solarization and steaming are acceptable for organic production.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. FLUOPICOLIDE
(Adorn)
Key Diseases
1–4 fl oz/100 gal water
12
Pythium Root Rot (11/20)
44
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
MODE OF ACTION GROUP NAME (NUMBER1): Benzamides (43)
COMMENTS: Toxic to aquatic organisms.
B.
C.
CYAZOFAMID
(Segway)
1.5–3.0 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Ubiquinone reductase, Qi site (21)
COMMENTS: Toxic to aquatic organisms.
FENAMIDONE
(Fenstop)
7–14 fl oz/50–100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Toxic to aquatic organisms.
12
12
D. BOSCALID/PYRACLOSTROBIN
(Pageant)
12–18 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
E.
F.
REYNOUTRIA SACHALINENSIS#
(Regalia CG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Anthraquinone elicitor (P 05)
4
MEFENOXAM
0.5–1.0 fl oz/100 gal water
(Subdue Maxx)
48
MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)
COMMENTS: Applied at planting as a drench and periodically thereafter as needed. Available also in a
granular formulation to use before planting. It is water-soluble and readily leached from soil. It is absorbed
primarily through roots and may be translocated in the plant through the xylem. Use of this material over a
period of time may lead to resistance.
G. SALTS OR ESTERS OF PHOSPHOROUS ACID
(Aliette WDG)
2.5–5 lb/100 gal water for foliar application
12
MODE OF ACTION GROUP NAME (NUMBER1): Phosphonate (P 07)
COMMENTS: When applied as a foliar spray, it is absorbed by foliage and moves into roots. Soil drench is
less effective than a foliar application.
H. ETRIDIAZOLE
(Terrazole CA)
4–6 oz/100 gal
1
MODE OF ACTION GROUP NAME (NUMBER ): Heteroaromatics (14)
I.
GLIOCLADIUM VIRENS#
(SoilGard)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Microbial (BM 02)
12
4
1
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California,
make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a
fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two
consecutive applications before rotating to fungicide with a different mode of action group number.
#
Acceptable for use on organically grown ornamentals.
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Pythium Root Rot (11/20)
45
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
RUST (11/20)
Rust: Phragmidium spp., Puccinia spp., and others
SYMPTOMS AND SIGNS
Rust pustules appear as powdery masses of yellow, orange, purple, black, or brown spores on leaves and
sometimes on stems. Depending on the particular plant host, pustules can be found on either side of
leaves. Severe rust can result in dried, dead foliage. The most significant impact of rust disease is the reduction of quality and marketability of the commodity.
COMMENTS ON THE DISEASE
The rust fungi are obligate parasites in the order Uredinales. Some have complicated life cycles that include up to five different spore stages and two distinctly different hosts. Other rusts produce less than
five or sometimes only one type of spore and infect only one kind of plant. Stem rust (Puccinia graminis)
of wheat alternates between barberry (Berberis spp.) and wheat (Triticum vulgare) and all five spore stages
are produced. Rose rust produces four spore stages but only roses (Rosa spp.) are infected.
Urediniospores ("repeating" spores) are produced in pustules that appear yellow, orange, or brown as a
result of masses of spores. These spores can re-infect the same host that produces them, making them the
damaging phase of most rust diseases. Urediniospores are windborne and infect the plant through stomata. Water is required for short periods (6–8 hours or less) for germination and infection. Heavy dew is
often sufficient. Once infection has occurred, water is no longer needed for continued development, and
the infection and spore production will continue for the life of the leaf.
Some rusts, including rose (Phragmidium tuberculatum) may survive the winter on leaves that do not fall
off the plant. Rose rust also survives as teliospores (dark, thick–walled, overwintering spores) that form
in fall. These spores survive in a dormant stage on fallen leaves.
MANAGEMENT
Rust diseases are favored by moderate temperatures that favor the growth of the host. Rust spores can be
killed by high temperatures. Some rust infections, such as geranium rust (Puccinia pelargonii-zonalis), can
be eradicated by hot water treatment of cuttings, although some damage to the host can occur.
Because water is necessary for infection, overhead irrigation should be avoided when rust is a problem.
Eliminate alternate hosts.
Chrysanthemum white rust, caused by Puccinia horiana, and Gladiolus rust, caused by Uromyces transversalis, are under an eradication program in California. Gladiolus rust also causes disease on other members
of the iris family such as Crocosmia, Tritonia, and Watsonia. See specific guidelines under the DISEASE
CONTROL OUTLINE FOR CHRYSANTHEMUM and DISEASE CONTROL OUTLINE FOR
GLADIOLUS.
There are several fungicides that can be used to protect plants from infection. Mancozeb as a protectant
and myclobutanil as an eradicant are generally effective against all rusts while triadimefon is effective
against only specific rusts.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
A. TEBUCONAZOLE
(Torque)
4–10 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant.
Key Diseases
Rust (11/20)
46
Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
B.
MANCOZEB
(Dithane 75 DF)
1–1.5 lb/100 gal water
24
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 03)
COMMENTS: Provides protection only; must be applied before infection. Protects against leaf spots, Botrytis,
rusts, and blight. Thorough coverage is important for control.
C.
MYCLOBUTANIL
(Rally 40WSP)
3 oz/50 gal water
24
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant of rusts or powdery mildew on carnations, crape myrtle, gerbera, roses, and snapdragons.
D. BOSCALID/PYRACLOSTROBIN
(Pageant)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
E.
F.
FLUOXASTROBIN
(Disarm 480 SC)
1–4 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
12
TRIADIMEFON
(Bayleton Flo)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A long-lasting systemic fungicide that provides for general control of some powdery mildews,
some rusts, and leaf blight and spots in greenhouses and commercial nurseries. Because this material is closely
related to growth retardant materials, it can have a toxic effect on certain plants, such as greenhouse roses.
G. AZOXYSTROBIN
(Heritage)
1–4 oz/100 gal water
4
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Apply as a broadcast or banded spray targeted at the foliage or crown of the plant. A locally
systemic fungicide that is effective against rusts.
H. REYNOUTRIA SACHALINENSIS#
(Regalia CG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Anthraquinone elicitor (P 05)
4
I.
WETTABLE SULFUR#
1–3 lb/100 gal water
24
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 02)
COMMENTS: Use a wetting agent. Not as effective as other materials. Apply this material with caution when
temperatures exceed 85°F.
J.
CHLOROTHALONIL
(Chlorothalonil 720 SFT)
1.375 pt/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M 05)
COMMENTS: Provides protection only; must be applied before infection.
12
K.
PROPICONAZOLE
(Banner Maxx II)
2–16 fl oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: Controls white rust of chrysanthemums but may cause phytotoxic symptoms on some cultivars.
L.
NEEM OIL
(Triact 70)#
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): (NC)
Key Diseases
4
Rust (11/20)
47
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
COMMENTS: Registered for landscape and nursery ornamentals, neem has some protectant properties against
rust, but is not effective for rust on rose. Apply on a 14-day schedule.
*
1
Permit required from county agricultural commissioner for purchase or use.
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action.
Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make
no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
#
Acceptable for use on organically grown ornamentals.
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
Key Diseases
Rust (11/20)
48
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
SOUTHERN BLIGHT (11/20)
Sclerotium rolfsii
SYMPTOMS AND SIGNS
Southern blight, also called southern wilt, southern stem rot, southern root rot and other names, results
from infection by the soilborne fungus Sclerotium rolfsii. The fungus survives in the soil as small (0.04–0.08
inch), tan to brown, round sclerotia. The sclerotia resemble mustard seeds in size and color and the fungus is sometimes referred to as the "mustard seed fungus." Plants are attacked at the soil line or below
ground. The fungus produces abundant white hyphae or mycelia around infected parts and in and on the
soil. Sclerotia are formed by the mycelia on infected plant parts and in the soil; their presence is the main
diagnostic feature of the disease. The initial symptoms are similar to those caused by other basal stem rots
(cottony rot, Rhizoctonia stem rot, etc.): discolored crown/stem lesion at the soil line, discoloration of
lower leaves, wilting, plant collapse, and death.
COMMENTS ON THE DISEASE
The disease is favored by warm moist soil, hence it occurs in the summer months. The fungus has a wide
host range and includes many field, vegetable, and ornamental crops. This pathogen is a regulated pest in
California nurseries and must be eradicated. Contact your County Agricultural Commissioner for details.
MANAGEMENT
Steam (at 140°F for 30 minutes), solarize (double-tent at 160°F for 30 minutes or 140°F for 1 hour), or
chemically treat growing medium for container-grown plants.
For outdoor field production, soil fumigation or soil solarization (in warmer climatic areas) is effective in
killing soilborne sclerotia. Bulbs and other planting stock may carry the fungus. The fungus is killed by
exposure to 122°F for 30 minutes and some plant materials such as caladium tubers, iris rhizomes, and
gladiolus corms can be treated successfully with hot water. Use of heat treatment (steam, solarization,
and/or hot water) is acceptable for organic production.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing
a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and
environmental impact. Always read the label of the product being used.
SOIL FUMIGATION
A. CHLOROPICRIN*
Label rates
See label
COMMENTS: Inject into soil and cover immediately with plastic tarps. Fumigants are a source of volatile organic compounds (VOCs) but are not reactive with other air contaminants that form ozone. Fumigate only as a
last resort when other management strategies have not been successful or are not available.
SOIL FUNGICIDE
A. TEBUCONAZOLE
(Torque)
4–10 fl oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
COMMENTS: A systemic fungicide applied as a foliar spray; both a protectant and eradicant.
B.
CYPRODINIL/FLUDIOXONIL
(Palladium)
2–4 oz/100 gal water
12
MODE OF ACTION GROUP NAME (NUMBER1): Amino acids and protein synthesis (9) and signal transduction (12)
C.
FLUTOLANIL
(Prostar 70 WG)
3–6 oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Succinate-dehydrogenase inhibitor (7)
Key Diseases
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D. PCNB
(Terraclor 400)
Label rates
12
MODE OF ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)
COMMENTS: Helpful in preventing infection when incorporated into top 2 inches of soil. Best available material for southern blight caused by Sclerotium rolfsii. Insoluble in water and must be thoroughly mixed with
soil to reach its desired depth of control. Works through vapor action and has good residual action. Germination of some seeds may be inhibited and small plants may be stunted by this fungicide.
*
1
§
‡
Permit required from county agricultural commissioner for purchase or use.
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action.
Fungicides with a different group number are suitable to alternate in a resistance management program. In California,
make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a
fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two
consecutive applications before rotating to fungicide with a different mode of action group number.
Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements, which may be lower than maximum label rates.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing.
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SUDDEN OAK DEATH AND RAMORUM BLIGHT (11/20)
Phytophthora ramorum
SYMPTOMS AND SIGNS
Although hosts of P. ramorum show a range of foliar symptoms, the disease is generally characterized by
irregular, necrotic leaf lesions, instead of distinct leaf spots. Leaf infections can spread to the petiole and
twigs, but diseased leaves often fall off before the lesion reaches the petiole. Sometimes infections occur
initially on stems or develop into stems, where associated leaves eventually wilt, become necrotic, and
die. On some hosts, a fairly distinct dark line can mark the advance of leaf infection, especially in cool and
wet conditions.
Symptoms are most often found on leaf tissue where free water remains for long periods: leaf tips, leaves
hanging down or located deep within the canopy, leaves near or touching the soil, or leaves that overlap
or are cupped. Root infections are possible on some hosts, but the roots often appear more or less healthy.
Root rot symptoms, typical of infections by other Phytophthora species, are not seen. The importance of
these cryptic root infections in the spread of P. ramorum in the nursery trade is not yet clear.
While not commonly seen on nursery hosts, bark cankers on the trunks of woodland trees, such as oak
and tanoak, are also associated with this disease. Cankers have red-brown to black discoloration, dark
black to reddish colored sap, and often develop 3 to 6 feet above the ground, although they can be higher
or lower. Symptoms caused by fertilizer burn, chemical injury, drought injury, freeze damage, sunburn,
and root damage can sometimes look like P. ramorum foliar infection. However, these abiotic injuries are
often found distributed over the entire plant, while lesions caused by P. ramorum are often only found initially on a few leaves or on one portion of the plant. There are many damaging species of Phytophthora
other than ramorum, so diagnosis by a qualified lab is extremely important.
COMMENTS ON THE DISEASE
In the mid to late 1990s, portions of woodlands in Marin, Santa Cruz, and Monterey counties changed
dramatically. Tree crowns turned brown within a few weeks, giving the impression of instantaneous
mortality. Since then more than a million tanoaks, (Notholithocarpus [=Lithocarpus] densiflorus), California
black oaks (Quercus kelloggii), coast live oaks (Quercus agrifolia), and other oak species have died as a result of P. ramorum infection in northern and central California. The pathogen also causes mortality in forested regions of southern Oregon. Additionally, it can be found in streams as well as the natural waterways of Washington.
A distinct European lineage of P. ramorum is causing similar diseases on ornamentals in some nurseries,
botanic gardens, and landscapes in Europe. It has been infecting Vaccinium spp. in the heathlands of Scotland and Wales. Oak, and especially Japanese larch plantations, have been heavily impacted in the United
Kingdom.
Camellias, rhododendrons, viburnums, Pieris spp., and other popular ornamental plants are susceptible
to P. ramorum infection, and the pathogen can move long distances through shipments of infected nursery
stock. Federal and state quarantines are in effect that require nursery inspections. If the pathogen is
found, affected nursery stock must be destroyed. For a current host list and additional regulatory information, refer to the U.S. Department of Agriculture Animal and Plant Health Inspection Service’s website
on P. ramorum.
BIOLOGY
Phytophthora ramorum, while having many features in common with fungal organisms, is not a true fungus. Phytophthora species are Oomycetes or "water molds" and require a moist environment to actively
grow and reproduce. Phytophthora ramorum produces several reproductive structures important for pathogen spread and survival, including sporangia, zoospores, and chlamydospores. Sporangia give rise to
the zoospores, which can swim in water. Chlamydospores are resting spores that help the pathogen survive extreme temperatures, dryness, and other harsh conditions. Phytophthora ramorum can grow within a
temperature range of 36° to 80° F with an optimum temperature of 68° F.
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Spores can form on leaf surfaces of susceptible leaves and twigs following prolonged wetting. They are
moved from plant to plant via windblown or splashed rain or by direct contact with infected leaves.
Spores produced on infected plants can move to healthy plants in water runoff created by rain or sprinkler irrigation water. In California forests the pathogen sporulates prolifically on California bay laurel
trees (Umbellularia californica), which serve as reservoirs for inoculum. Infected California bay laurel can
also be an important source of inoculum when near the nursery stock.
MANAGEMENT
There are federal and state quarantines that require inspections for nursery stock in regulated California
counties. If the pathogen is detected, the affected plants are destroyed and the pathogen is eradicated.
Disease symptoms may take weeks to several months to develop and become apparent, so infected plants
may appear healthy at first. Fungicides that have activity on Phytophthora might prevent new infections
and therefore interfere with detection of this pathogen; it is best not to apply fungicides while evaluating
the disease status.
For most nurseries, the foremost objective of pest management programs is to prevent the introduction of
the pathogen into the nursery via infected plant material. This can be partly accomplished by careful inspection of all incoming host propagative material and stock.
• Monitor new outside source stock at least biweekly in summer and at least weekly during rainy
periods when environmental conditions are highly conducive to pathogen infection and development.
For nurseries surrounded by native host trees and shrubs and in the vicinity where P. ramorum is found,
monitor areas surrounding the nursery, especially wet areas, near puddles, or rain runoff zones. It is very
important to detect the pathogen early, while it is still at very low levels.
• Periodically inspect nearby native hosts for disease symptoms. Infected California bay laurel trees
near the perimeter of nurseries may produce inoculum that can spread and cause infection of
nearby host plants, so removal of these trees may be warranted.
• Consider building berms to prevent water and soil movement into production areas from hillsides
surrounding the nursery that may contain infected hosts.
• Irrigation water pumped from streams and ponds in areas of infected native hosts may be contaminated with P. ramorum. Consider having this water periodically tested to detect P. ramorum. If it is
found to be present, use alternative irrigation sources, such as well water or water disinfection
treatments.
For more information on developing a detection and monitoring program, see Nursery Guide for Diseases
Caused by Phytophthora ramorum on Ornamentals: Diagnosis and Management, UC ANR Publication 8156.
Cultural Practices
Cultural practices that can be useful to reduce disease risk:
• Avoid irrigation practices that leave foliage wet for prolonged periods. If sprinklers are used, irrigate in the morning to allow for thorough and quick drying of foliage.
• Monitor and maintain irrigation systems to insure the most uniform application of water to the
crop. Correct low spots, areas of poor drainage, and clogged or leaking irrigation heads.
• Monitor irrigation-water sources, other than well water, for P. ramorum. Use disinfection systems
if using recycled water.
• Wounded leaves (even tiny wounds or scratches) are much more susceptible to infection. Avoid
handling host plants if they might be wounded when environmental conditions favor disease.
• Avoid splashing water from soil to foliage, as well as from foliage to soil or container soil. Use
raised benches, gravel, or other means to elevate susceptible plants above soil. Transplants, even
on gravel beds, appear to be very susceptible to disease because of the close proximity of foliage to
soil, runoff water, or rain splash. Raised benches may be warranted for transplants.
• Remove plants or plant parts that are suffering from poor vigor, disorders, or other serious problems from production areas and destroy them. A small number of plants or plant parts could be
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•
•
bagged and disposed. If a cull pile is needed temporarily, cover it with a clear polyethylene sheet
until the culls can be destroyed or composted.
Propagate cuttings only from disease-free hosts.
Use only new or disinfested containers and soil. Place potting soil piles as far from infected native
hosts or cull piles as possible and covered with clear polyethylene sheeting. Do not mix potting
soil components on bare soil.
Monitoring and Treatment Decisions
Fungicides used to protect nursery stock from P. ramorum function as preventive treatments only. Currently, even the most active fungicides do not stop the development of P. ramorum once foliar lesions are
present. The use of Phytophthora-specific fungicides may be warranted for high risk situations, such as
where a nursery is exposed to local inoculum sources from surrounding infected native hosts or where P.
ramorum has been detected previously in the nursery. Fungicides should only be used after other management strategies and preventive steps have been fully implemented.
When applying fungicides, good coverage over the foliage is important; add a wetting agent to prevent
significant run-off and loss of fungicides on the hard-to-wet leaves of certain plant species. Apply treatments before environmental conditions favor pathogen infection; for example, spraying before a period of
rainy weather will allow water to linger on leaf surfaces for many hours.
Some fungicides applied to the foliage move into leaves and are not washed off by rain or sprinkler irrigation, while others provide a protective layer of chemical on the leaf surface. Some can be applied to the
soil, where they are absorbed and moved upward to the leaves, to protect them from infection. Some
have residual activity that can last for several weeks after they are applied. Read fungicide labels and
technical information provided by the fungicide manufacturer to learn how the fungicide can be used
most effectively. See PHYTOPHTHORA ROOT AND CROWN ROTS and management in this section.
Resistance management.
To help reduce the potential for the development of resistance by P. ramorum to fungicides, alternate or
tank mix fungicides with different mode-of-action group numbers. Fungicides active on P. ramorum may
already be used in the nursery to control other foliar or soil-inhabiting Phytophthora species or related
pathogens (such as downy mildews), and their use should be considered in planning the overall fungicide resistance management program.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees,
and environmental impact. Always read the label of the product being used.
A. CYAZOFAMID
(Segway)
3.0–6.0 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Ubiquinone reductase, Qi site (21)
COMMENTS: Toxic to aquatic organisms.
B.
C.
DIMETHOMORPH
(Stature SC)
12.25 fl oz/100 gal
MODE OF ACTION GROUP NAME (NUMBER1): Carboxylic acid amides (40)
12
12
MEFENOXAM
(Quali-Pro Mefenoxam 2 AQ)
Label rates
48
MODE OF ACTION GROUP NAME (NUMBER1): Phenyl amides (4)
COMMENTS: The granular formulation may be applied preplant or the liquid formulation can be applied as
a drench at planting. Mefenoxam is water-soluble and readily leached from soil. It is absorbed primarily
through roots and may be translocated in the plant through the xylem.
D. MANDIPROPAMID
(Micora)
Key Diseases
4–8 fl oz/100 gal
4
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MODE OF ACTION GROUP NAME (NUMBER1): Carboxylic acid amides (40)
E.
F.
FLUOPICOLIDE
(Adorn)
1–4 fl oz/100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Benzamides (43)
COMMENTS: Toxic to aquatic organisms. Drench application.
12
FENAMIDONE
(Fenstop)
7–14 fl oz/50–100 gal water
MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
COMMENTS: Toxic to aquatic organisms.
12
G. BOSCALID/PYRACLOSTROBIN
(Pageant)
12–18 oz/100 gal
12
MODE OF ACTION GROUP NAME (NUMBER1): Carboximide (7) and quinone outside inhibitor (11)
H. SALTS OR ESTERS OF PHOSPHOROUS ACID
(Aliette WDG)
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): Phosphonate (P7)
1
‡
12
Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating
to a fungicide with a different mode of action group number; for fungicides with other Group numbers, make no more
than two consecutive applications before rotating to fungicide with a different mode of action group number.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can
be safely entered without protective clothing.
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Sudden Oak Death (11/20)
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VERTICILIUM WILT (11/20)
Verticillium wilt: Verticillium albo-atrum, Verticillium dahliae
SYMPTOMS AND SIGNS
Symptoms vary somewhat with the kind of plant and the environment, but some symptoms are common to
most situations. The leaves may wilt and turn yellow, first at the margins and between the veins, then they
turn tan or brown and die starting from the base to the tip of the plant or branch. Dead leaves can either fall off
or remain attached to the plant. Woody plants often are affected first on one side, and affected branches usually die. The water-conducting tissues (xylem) of infected plants are often discolored with dark brown to black
streaks. In some plants, including olive, ash, and roses, there is little or no discoloration.
COMMENTS ON THE DISEASE
Verticillium wilt, one of the most widespread and destructive soilborne diseases of plants, affects a large
number of herbaceous and woody species throughout the world. The causal fungus, Verticillium dahliae,
infects susceptible plants through the roots and plugs the water conducting tissues.
Susceptible flower crops include China aster, chrysanthemum, cineraria, dahlia, geranium, gerbera, heather,
marigold, peony, pelargonium, rose, snapdragon, statice, stock, and strawflower. The V. dahliae fungus forms
microscopic black resting structures (microsclerotia) capable of surviving in soil for many years in the absence
of a susceptible plant. When a susceptible plant is planted in infested soil, the microsclerotia germinate and infect the plant. Long rotations with nonsusceptible plants are not effective in controlling the fungus.
The fungus also produces conidia that can be transported in irrigation water; however, they are not longlived. The fungus can be disseminated by leaves dropping from infected plants and being blown around
by the wind.
MANAGEMENT
Many horticultural crop plants have been selected or bred for resistance to the fungus. Use resistant cultivars
and pathogen-free plants whenever possible.
Steam (at 140°F for 30 minutes), solarize (double-tent at 160°F for 30 minutes or 140°F for 1 hour), or chemically treat growing medium. For outdoor cut flower or nursery production, avoid fields previously used for
susceptible crops (e.g., tomato, cotton, potatoes, strawberries, as well as the ornamentals listed above) unless
disinfected. Soil fumigation or soil solarization (in warmer climatic areas) can be useful. During the growing
season, remove and destroy any plants that exhibit symptoms of Verticillium wilt.
Common name
(Example trade name)
Amount to use
REI‡
(hours)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value
listed first–the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide’s properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
SOIL FUMIGATION
A. CHLOROPICRIN*
Label rates
See label
Allowable for use under a Critical Use Exemption only. Fumigants are a source of volatile organic compounds
(VOCs) but are not reactive with other air contaminants that form ozone. Fumigate only as a last resort when
other management strategies have not been successful or are not available.
B.
Sequential application of:
(Note: Fumigants such as 1,3-dichloropropene and metam products are a source of volatile organic compounds (VOCs) but
minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management
strategies have not been successful or are not available.)
CHLOROPICRIN*/1,3 DICHLOROPROPENE*
(Pic-Clor60)
(Pic-Clor60 EC)
Key Diseases
300–332 lb (shank)
200–300 lb
See label
See label
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COMMENTS: Very effective for control of soilborne fungal pathogens and insects. Drip irrigation requires an
emulsifier. For shank fumigation, using higher rates or plastic mulch, especially virtually impermeable film
(VIF), improves weed control. For drip fumigation the use of VIF will improve both nematode and weed control.
According to state permit conditions, the maximum application rate of 1,3-dichloropropene is 332 pounds active
ingredient per acre. Pic-Clor60: One gallon of weighs 12.1 lb; Pic-Clor60 EC: One gallon of weighs 11.8 lb.
Following 5 to 7 days after fumigation:
METAM SODIUM*
(Vapam HL, Sectagon 42)
37.5–75 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains 4.26 lb
of metam sodium.
. . . or . . .
METAM POTASSIUM*
(K-Pam HL, Sectagon–K54)
30–45 gal
See label
COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains 5.8 lb of
metam potassium.
C.
DAZOMET*
(Basamid)
200 lb
See label
COMMENTS: Powder incorporated into the soil, followed by irrigation or tarping. It decomposes to a gaseous
fumigant (methyl isothiocyanate).
SOIL FUNGICIDES
A. REYNOUTRIA SACHALINENSIS
(Regalia CG)#
Label rates
MODE OF ACTION GROUP NAME (NUMBER1): anthraquinone elicitor (P 05)
*
§
‡
4
Permit required from county agricultural commissioner for purchase or use.
Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements,
which may be lower than maximum label rates.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely
entered without protective clothing.
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VIRUSES AND VIROID DISEASES (11/20)
SYMPTOMS AND SIGNS
Virus diseases are recognized by several characteristic symptoms. Light and dark green mosaic patterns,
mottles, ringspots, distortion of leaves and other plant parts, vein clearing, and vein enations are some of
the symptoms seen in the leaves. Deformed, yellow, stunted growth, or overall stunting are other possible symptoms.
COMMENTS ON THE DISEASE
Viruses multiply only in living cells. They are too small to be seen with a light microscope and are therefore considered to be submicroscopic. Viruses are composed of a nucleic acid (most plant viruses contain
ribonucleic acid [RNA]) and are enclosed in a protein coat. The nucleic acid of a few plant viruses (Carnation etched ring virus, Dahlia mosaic virus) is deoxyribonucleic acid (DNA). Viroids consist of low molecular
weight RNA that lacks a protein coat. Chrysanthemum stunt viroid and Chrysanthemum chlorotic mottle viroid are examples of viroids.
Positive identification of virus infection involves several procedures, including visualization of virus particles with the electron microscope, serological techniques such as ELISA (enzyme-linked immunosorbance assay), sap inoculations of indicator plants, budding and grafting to indicator plants, microscopic
examination for inclusion bodies (aggregates of virus particles or virus-induced protein structures), RNA
and DNA hybridization, polymerase chain reactions (PCR), and gel electrophoresis.
Many viruses enter the host plant via the feeding activity of vectors that transmit the virus into plant
cells. Insects, especially aphids, whiteflies, and leafhoppers, vector many viruses. Thrips vector Tomato
spotted wilt virus and Impatiens necrotic spot virus. Mites, nematodes, and lower fungi also serve as vectors
of a few viruses. See the Viruses With Wide Host Ranges table for a list of common plant viruses and
their hosts, how they are spread, and links to photographs of their damage.
Most viruses are transmitted by vegetative propagation of new plant material from infected mother
plants. Many plant viruses and viroids are spread by physical contact or by tools. Some orchid viruses are
spread when healthy plants come in contact with diseased ones. Some viruses are pollenborne (Cherry leaf
roll virus, Prunus necrotic ringspot virus). A few viruses are seedborne (Squash mosaic virus in muskmelons,
Tomato mosaic virus in tomato, and others). Several viruses, including Tobacco mosaic virus, can survive in
water run-off from infected plants, which, when recycled and used as irrigation water, can result in new
infections.
MANAGEMENT
Control of virus diseases is a matter of prevention–the use of virus-free planting stock and resistant varieties. Once a plant is infected by a virus it usually remains infected for the life of the plant as there are no
available pesticide treatments. Plants vegetatively propagated from infected mother stock are usually infected. However, virus-free plants can be obtained from infected plants by a combination of heat treatment and shoot tip (meristem) culture, and sometimes with the aid of chemical inhibitors of virus multiplication. Some viruses are transmitted from plant to plant by means of the feeding activity of insects.
Once an insect has acquired a virus, it may retain it in a persistent (up to lifetime) or non-persistent (usually means minutes to hours) manner. Controlling insect vectors may help in reducing the spread of persistently transmitted viruses; however, with non-persistently transmitted viruses, insects can often spread
the virus before they are inactivated by insecticides. Remove weeds and other plants that may harbor the
virus and/or the vector.
Disinfection of pruning or propagation tools between cuts, or at least between different plant sets, varieties, or species, and the use of disposable gloves can help reduce the spread of virus diseases in a greenhouse operation. A solution of 1 part household bleach in 4 parts of water, applied for 5 minutes, acts as
an effective disinfectant for virus-contaminated materials (tools, benches, etc.). Bleach solutions must be
rinsed off with clean water to avoid toxicity to plants. (Note: Bleach treatments are corrosive to metal
tools.) See MANAGEMENT OF SOILBORNE PATHOGENS section for more details.
Cultural Control
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In outdoor field crop production, silver reflective mulch has been shown to repel aphids and whiteflies,
thus reducing their numbers in and around plant canopies. In addition, virus transmission by these insects was greatly reduced. For best results, apply mulches at the time of planting or transplanting the
crop. Apart from reducing aphid and virus incidence, silver reflective mulch increased cut flower production and reduced the crop requirement for irrigation water and fertilizer. This method is acceptable for
organic production.
Viruses with wide host ranges.
Ornamental hosts
Crop plant hosts
Weed and native
plant hosts
Virus
Transmission
Bean yellow mosaic
(potyvirus group)
aphids; mechanically gladiolus, sweet pea, violets legumes, bean, clovers,
to an extent in gladiofava bean, pea, soybean,
lus
sweet clover
legumes, Chenopodium, clovers, sweet clover
Beet curly top (geminivirus group)
leafhoppers
cosmos, coreopsis, geranium, nasturtium, petunia,
strawflower, stock, viola,
zinnia
bean, beets, borago, buckwheat, celery, clovers,
cress, cucurbits, fava bean,
fennel, flax, horseradish,
pepper, potato, radish, rhubarb, tobacco, tomato, vetch
Atriplex spp., Chenopodium
spp., clovers, Polygonum
spp., Rumex spp., Russian
thistle, shepherd's-purse
Cauliflower mosaic
(caulimovirus group)
aphids
honesty (lunaria), stock
crucifers, broccoli, cabbage, mustard, Raphanus spp.,
cauliflower, Chinese cabshepherd's-purse
bage, mustard
Cucumber mosaic
(cucumovirus group)
aphids; mechanically
in many hosts
begonia, buddleia, calenbuckwheat, carrot, celery,
dula, China aster, columcucurbits, cowpea, pepper,
bine, dahlia, daphne, delpotato, tobacco, tomato
phinium, geranium, gerbera,
gladiolus ligustrum, lily, lobelia, nasturtium, passionvine, primula, snapdragon,
vinca, viola, zinnia
commelina, lambsquarters, lupine, milkweed, nightshade,
penstemon, pigweed, pokeweed, tree tobacco (Nicotiana
glauca)
Prunus necrotic ringspot
(ilarvirus group)
grafting; pollen
Prunus spp., rose
apple, hops, Prunus spp.
Prunus spp.
Tobacco mosaic (tobamovirus group)
mechanical; seeds
delphinium, petunia, phlox,
may be externally
wisteria, flowering tobacco
contaminated, can be
soilborne
beans, tobacco, tomato,
peppers
Emilia, tree tobacco
artichoke, basil, bean, celery, clover, cowpea, endive,
fava bean, lettuce, papaya,
pea, peanut, pepper, pineapple, spinach, tobacco, tomato, and others
bindweed, chickweed, emilia,
jimsonweed, knotweed, lupine, malva, Mesembryanthemum, miner's lettuce, physalis, pigweed, nightshade,
shepherd's-purse, and others
Impatiens necrotic
thrips
spot and tomato spotted wilt (tospovirus
group)
amaryllis, aster, ageratum,
begonia, calendula, calla,
chrysanthemum, coreopsis,
cosmos, dahlia, forget-menot, gerbera, gladiolus, gloxinia, gypsophila, impatiens,
kalanchoe, lily, nasturtium,
nemesia, papaver, petunia,
phlox, primula, ranunculus,
salvia, stock, sweet pea, tagetes, verbena, zinnia, and
others
Turnip mosaic (potyvirus group)
anemone, nasturtium, petu- Brussels sprouts, cabbage, cruciferous weeds
nia, statice, stock, sweet wil- cauliflower, cress, horseradliam, wallflower, zinnia
ish, lettuce, mustard, radish,
rape, rhubarb, swede turnip
Key Diseases
aphids
Viruses and Viroid Diseases (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Disease Control Outlines
ASTER, CHINA
Callistephus chinensis (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Fusarium wilt*
(Fusarium oxysporum f. sp. callistephi)
Plants yellow and wilt, often on one side. Brown discoloration of vascular system develops. Disease also
causes damping-off of young seedlings at soil temperatures of 75° to 80°F.
Commonly seedborne. In soil for many years. Disease is
most severe when soil and/or air temperatures are high.
Use disease-free seed. Fumigate the seedbed with chloropicrin
or a sequential application of chloropicrin/1,3 dichloropropene
and metam sodium or solarize soil. Grow on clean land, or only
once every 5 years on infested land. Treat seed with a fungicide.
Gray mold*
(Botrytis cinerea)
Brown, water-soaked decay of flowers. Fuzzy gray
fungus spores form on rotted tissues. Fungus also attacks base of plant.
In plant debris. Favored by cool, wet conditions.
Avoid overhead irrigation. Mist blooms with iprodione or
fenhexamid.
Leaf spots
(Stemphylium callistephi)
Circular, irregular, brown spots appear on lower
leaves. Leaves may die.
In plant debris. Airborne spores require long (48 hrs),
damp periods for infection.
Avoid low-lying areas where air movement is poor. Do not use
overhead irrigation. Protect foliage with a fungicide such as
mancozeb.
Root rot
(Pythium* and
Phytophthora spp.*)
Plants wilt or suddenly collapse. Roots decay. Blackish discoloration of leaves, stems, and roots occurs.
Also causes damping-off of seedlings.
In soil. Favored by heavy, waterlogged soils.
Rust*
(Coleosporium asterum)
Orange pustules of powdery spores form on undersides of leaves. On living plants and possibly from
spores from alternate host (three-needle pines).
Favored by free moisture from rain, dew, or fog.
Avoid overhead irrigation. Treat at the first signs of rust and
continue until conditions are no longer favorable for the disease. Grow seedlings away from main crop.
Cottony rot or Sclerotinia rot
Infection girdles stems. Cottony, white fungal growth
and large, black sclerotia develop on and inside
stems. Stems take on a bleached-white color.
Airborne spores produced by sclerotia in soil, but infection
more common from growth of hyphae from sclerotia. Favored by wet weather.
Avoid overhead irrigation. Treat planting area with PCNB.
Spray plants with iprodione or thiophanate-methyl before rainy
periods and at 2- to 4-week intervals during wet weather. Remove plant debris from field.
Stem rot
(Rhizoctonia solani, Botrytis cinerea)
A brown decay develops at the soil line and affects
the basal leaves and stem.
Soilborne and in plant debris. Gray mold (B. cinerea) favored by cold, damp conditions. Disease development
can be rapid under high temperature conditions.
Before planting or transplanting, mix PCNB or Trichoderma
spp. into top inch of soil. Spray bases of seedlings with thiophanate-methyl, iprodione, or Trichoderma spp.
Verticillium wilt*
(Verticillium dahliae)
Symptoms are almost identical to Fusarium wilt. Not a
common disease of asters in California.
In soil for many years. Symptoms most severe during
warm weather that follows a cool period.
Avoid planting in fields where fungus has occurred or fumigate
soil as described for Fusarium wilt.
Virus or viruslike diseases
Symptoms
Host range and natural spread
Comments on control
Aster yellows*
(Aster yellows phytoplasma)
Infected plants produce an upright basal rosette of
yellow shoots. Sometimes one-sided. Flowers are deformed and remain green. Sporadic disease of asters
in California.
Aster yellows phytoplasma has a wide host range. Vectored by leafhoppers.
Locate seedbed away from weedy areas. Control weeds and
leafhoppers in noncropped areas.
(Sclerotinia sclerotiorum)
Disease Control Outlines
Aster, China (11/20)
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Illustrated version at http://ipm.ucanr.edu/PMG/selectnewpest.floriculture.html
UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
AZALEA
Rhododendron spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Cutting rot and graft decay
(Rhizoctonia solani and
Cylindrocladium scoparium)
Basal rot of cuttings occurs. Under humid conditions,
tops are rotted and covered with fungal strands (mycelium).
In soil and plant debris. Favored by moist conditions and
temperatures of 75° to 80°F.
Steam or chemically treat propagating media, flats, etc. Grow
stock plants in treated media and observe strict sanitation.
Spray or drench cuttings in rooting media with thiophanate-methyl or iprodione. Cylindrocladium is difficult to control
with fungicides; triflumizole can be used in enclosed commercial structures.
Flower blight
(Ovulinia azaleae)
Small, round spots rapidly enlarge and cause entire
flower to collapse. Rotted flower becomes soft and
clings to leaves or stems.
Black fungal structures (sclerotia) produced in diseased
flowers and survive in soil. Favored by cool, rainy weather
and by moisture on flowers. Spores are airborne.
Avoid overhead irrigation. Remove and burn diseased blossoms. Mulch soil with 4-inch layer. Treat soil with PCNB several weeks before plants bloom. Protect blossoms with thiophanate-methyl or triadimefon.
Leaf gall
(Exobasidium vaccinii)
All or part of leaf becomes greatly thickened, distorted, and crisp. Also affects flowers. Infected parts
are covered with a white or pinkish bloom of fungal
spores.
On living plants. Airborne spores produced only during
wet weather.
Hand-pick galls where practical before they turn white. Avoid
overhead irrigation. Protect foliage with a fungicide, such as
mancozeb, during wet weather.
Ramorum blight*
(Phytophthora ramorum)
Leaf lesions that vary in size from 0.2 inches to covering nearly half the leaf. Lesions primarily at leaf tip or
edge; can be surrounded by diffuse margins or thick
black zone line. Infected leaves drop prematurely and
lower part of plant can defoliate. Symptoms may be
confused with leaf scorch in areas of high heat/sun.
Spore structures commonly form on leaf surfaces and
twigs, following prolonged wetting. They are moved in
contaminated soil, from plant to plant via windblown rain,
or by direct contact with infected leaves.
Monitor incoming stock and areas surrounding the nursery for
symptoms, follow good cultural and sanitation practices, and
use preventive treatments before environmental conditions favor development of the pathogen.
Root rot
(Pythium* and
Phytophthora spp.*)
Plants are low in vigor. Leaves wilt and turn dull
green and fall prematurely, so only a few terminal
leaves remain on the plant. Plants frequently die.
Wood under bark at soil line is discolored. Roots become discolored and rotten (Pythium). Root and basal stem rot
(Phytophthora).
Water molds occur in soil. Favored by overwatering, poor
drainage, and other factors that weaken plants.
Treat growing media with chloropicrin or other recommended
fumigants. Select cuttings from high on stock plants. Drench
plants with oomycete (water mold) specific fungicide, or spray
with fosetyl-Al.
Septoria leaf spot or leaf scorch
(Septoria azaleae)
Dark, reddish brown, angular spots appear on leaves,
which fall prematurely. Leaves yellow on some cultivars.
On living and dead leaves. Favored by wet weather. Fungal spores spread in splashing water.
Avoid overhead irrigation. Protect foliage with a fungicide such
as mancozeb or thiophanate-methyl.
Azaleas are also susceptible to crown gall* (Agrobacterium tumefaciens), gray mold* (Botrytis cinerea), powdery mildew* (Erysiphe sp.), and web blight (Rhizoctonia solani).
* For additional information, see section on Key Diseases.
Disease Control Outlines
Azalea (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
BEGONIA
Begonia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial leaf spot
(Xanthomonas campestris pv.
begoniae)
Circular, necrotic spots start as small, water-soaked,
blisterlike spots. Premature abscission occurs when
spots are numerous.
Systemic as well as in dead begonia leaves. Favored by
splashing water or overhead irrigation and high temperatures (80° to 90°F).
Keep humidity low. Avoid wetting foliage. Do not crowd plants.
Remove and destroy infected plants.
Gray mold*
(Botrytis cinerea)
Soft, brown rot of leaves, stem, and flowers occurs.
Fuzzy gray fungal spores form on decayed tissues.
Fungus is common on weakened plants. Botrytis may
also start in powdery mildew spots, sunburned tissues, tissues injured by other means, or in ligules.
In plant debris; common on any dead plant material on
soil if moist. Resting sclerotia favored by high moisture
conditions and low temperatures.
Control root rots and powdery mildew*. Pick up dead flowers
and leaves. Keep humidity low. Protect plants with fungicide
such as fenhexamide. Avoid overhead irrigation.
Powdery mildew*
(Erysiphe begoniicola,
Golovinomyces orontii)
White, powdery spots develop on upper and lower
leaf surfaces and small, greasy spots occur on undersides of leaves. Also may appear on flowers of some
fibrous begonias.
On living begonia leaves; rarely as resistant fungal structures (chasmothecia). Spores are airborne as well as
spread in water, but do not survive in free water. Favored
by moderate temperatures and shade. Common on plants
as they senesce in fall.
Increase air movement; some resistant cultivars available.
Spray at the first sign of mildew and at 2- to 3-week intervals
thereafter. Use myclobutanil, or triadimefon. Triadimefon is
very effective but expect stunting of some plants.
Root and stem rot*
(Pythium spp.)
Plants are stunted, unthrifty, and may die. Root system is small and discolored. Also invades tubers of
tuberous begonias. Stem rot phase: stems become
water soaked and discolored, and collapse. Disease
also causes damping-off of seedlings. Plants are predisposed to sunburning.
In soil. Spores spread in water and when infested soil is
moved to uninfested areas. Favored by excess water.
Steam or chemically treat soil. Observe strict sanitary
measures. Drench plants with oomycete (water mold) specific
fungicide. Do not drench very young seedlings.
Virus or viruslike diseases
Symptoms
Host range and natural spread
Comments on control
Spotted wilt
(Tomato spotted wilt virus)
Rings or zoned spots develop on leaves. Plants are
stunted; flowers are of poor quality.
Infects begonias, nasturtiums, callas, dahlias, and some
weeds. Transmitted by thrips.
Eliminate nearby weeds and susceptible ornamental plants.
Control thrips.
Begonias are also susceptible to Armillaria root rot (Armillaria mellea), anthracnose (Gloeosporium sp.), black root rot (Thielaviopsis basicola), cottony rot* (Sclerotinia sclerotiorum), crown gall* (Agrobacterium tumefaciens), foliar nematode**
(Aphelenchoides olesistis), leaf spot (Phyllosticta sp.), Rhizoctonia stem rot (Rhizoctonia solani), root knot nematode** (Meloidogyne spp.), soft rot (Pectobacterium (=Erwinia) carotovorum), and Verticillium wilt* (Verticillium dahliae).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
Begonia (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
CALLA
Zantedeschia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Crown rot (Rhizoctonia solani)
Base of stems of callas are infected at or below the
soil line, causing a general chlorosis of foliage.
Favored by warm, moist conditions. Fungus is present in
most field soils.
Avoid deep planting and overwatering. Treat soil with PCNB
before planting.
Pythium rot* (Pythium ultimum)
Roots may rot first. Pink and yellow corms develop irregular-shaped, shallow, water-soaked lesions that
may coalesce. Infection spreads into interior tissues
of root structures, producing irregular-shaped gray lesions that are sharply delimited.
Pathogen enters root structures through wounds. It is present in many field soils and has a wide host range. Disease is favored by warm, moist conditions, heavy soils,
and poor drainage.
Avoid injuries to the rhizomes. Clean and dry root structures
soon after digging. Store below 50°F. Some of the water mold
fungicides would probably be effective in controlling the disease.
Phytophthora root rot*
Yellowing of leaf margins of outer leaves followed by
general yellowing and wilting. Feeder rootlets are rotted.
Pathogen is present in some field soils. Several other
types of plants may be infected. Favored by wet soil conditions.
Grow on raised beds and provide good drainage. Do not overirrigate. Treat with oomycete (water mold) specific fungicide.
A soft rot of the rhizomes. Plants may rot off at the
soil line. Bacterium is a common secondary invader
of succulent plant parts and generally requires some
sort of injury to cause disease. Has odor.
Bacterium is present in some field soils. Favored by
warm, moist conditions and plant parts attacked by other
organisms.
Avoid injuries to the rhizomes. Do not overwater. Yellow callas
are more susceptible than others, but there are new yellow
cultivars that are more resistant.
(Phytophthora cryptogea)
Soft rot (Pectobacterium (=Erwinia) carotovorum)
Virus or viruslike diseases
Symptoms
Host range and natural spread
Comments on control
Dasheen mosaic
(Dasheen mosaic virus)
Mosaic patterns in leaves, which may be severely distorted. Infects plants low in vigor.
Common because callas frequently propagated vegetatively, which spreads the virus. Virus is spread by aphids.
Spread in a planting can be rapid. Can be transmitted by
sap but not by seed.
Obtain or develop virus-free plants by heat treatment and tissue culture. Control aphids. Remove infected plants.
Spotted wilt
(Tomato spotted wilt virus and
Impatiens necrotic spot virus)
Foliage, petioles, and flower stalks are streaked or
spotted by whitish or yellowish areas, and sometimes
by small, concentric rings. Necrotic areas that develop in leaves may be colonized by secondary fungi.
Sometimes the necrotic areas are attributed to fungi,
but usually they are secondary invaders.
Common because callas frequently propagated vegetatively, which spreads the disease. Both viruses are also
transmitted by several thrips species. Virus is acquired by
nymphal stage and transmitted by adult throughout its life.
The virus has a very wide host range including many
weeds and ornamental plants.
Control weeds and thrips. Destroy infected callas.
Callas are also susceptible to leaf spots (Gloeosporium callae, Coniothecium richardiae, and Cercospora richardiae), powdery mildew* (Oidiopsis taurica), Armillaria root rot* (Armillaria mellea), gray mold* (Botrytis cinerea), Phytophthora spp.,
seedling rot (Rhizoctonia solani), southern blight* (Sclerotium rolfsii), and root knot nematode** (Meloidogyne spp.)
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
CAMELLIA
Camellia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Dieback
(Glomerella cingulata)
Wilting and dying of branches. Leaves darken and often remain attached. Branch is girdled by fungus that
enters through injuries, including leaf scars.
Found in warmer areas of California. Favored by wet,
warm conditions, weakened plants, and injuries. Fungus
spores (conidia) are spread by splashing water. Fungus
has a wide host range.
Prune diseased tissues and protect wounds with a fungicide
such as captan. Avoid overwatering.
Flower blight
(Ciborinia camelliae)
Flowers have dry rot with accented veins. Only petal
tissues are infected. First symptoms are small tan or
brown necrotic spots in the center of the flower that
enlarge and move rapidly to the base of flower. Rotted
flowers are heavy and easily fall to ground. The fungus continues to develop, forming sclerotia in the calyxes of infected flowers.
Sclerotia survive on or in soil and germinate for several
years producing fruiting bodies (apothecia) that discharge
spores (ascospores) forcibly into the air.
Where practical, pick up all blossoms because fallen blossoms
either may be infected or may become infected while on the
ground. Prevent sclerotia from germinating by spraying ground
with PCNB annually. Thiophanate-methyl will protect petals
from infection but sprays must be applied frequently as new
flowers open. Mulches 4 inches or more deep will help prevent
apothecia from reaching the surface.
Gray mold*
(Botrytis cinerea)
Necrotic, brown spots. Rot does not move to the base
of the flower as rapidly as the flower blight fungus.
Fuzzy gray fungus spores form on decayed blossoms
under high humidity.
Favored by cool wet weather. Spores are airborne. Fungus survives on and in old flowers.
Avoid overhead irrigation. Clean up plant debris, especially floral tissues. Protect flowers with a fungicide effective against
Botrytis such as fenhexamid.
Phytophthora root rot*
(Phytophthora spp.)
Plants stunted and low in vigor. Foliage yellows, plant
wilts and dies. Roots rotted. When plants collapse, the
stem is girdled at or below the soil line. Phytophthora
cinnamomi is often involved but other species also infect camellias.
Phytophthora spp. survive in soil as resting spores. They
are common in stream and ditch water. Infective spores
(zoospores) swim very short distances in soil water. Disease is favored by poor drainage, long wet periods, and
standing water.
Heat or chemically treat propagation and growing media.
Drench plants on a preventative basis with oomycete (water
mold) specific fungicide.
Ramorum blight1
Leaf lesions that vary in size from 0.2 inches to covering nearly half the leaf. Lesions primarily at leaf tip or
edge; can be surrounded by diffuse margins or thick
black zone line. Infected leaves drop prematurely and
lower part of plant can defoliate. Symptoms may be
confused with leaf scorch in areas of high heat/sun.
Spore structures commonly form on leaf surfaces of susceptible leaves and twigs following prolonged wetting.
They are moved in contaminated soil, from plant to plant
via windblown rain, or by direct contact of infected leaves.
Monitor incoming stock and areas surrounding the nursery for
symptoms, follow good cultural and sanitation practices, and
use preventive treatments before environmental conditions favor development of the pathogen.
(Phytophthora ramorum)
Camellias are also susceptible to several viruses and viroids such as color break virus and golden ring spot complex.*
* For additional information, see section on Key Diseases.
1
Phytophthora ramorum was isolated from the following C. japonica cultivars on two or more occasions: Bob Hope, Mrs. Charles Cobb, Daikagura var. Debutante, Elegans Splendor, Glen 40, Kumasaka, Kramer's Supreme, Mathotiana Supreme, Nuccio's Gem, Nuccio's Pearl, Silver Waves, Shiro Chan, Tom Knudsen, P. ramorum was isolated from the following C. sasanqua cultivars on two or more occasions: Apple Blossom, Cleopatra, Hana Jiman, Jean May, Kanjiro,
Setsugekka, Yuletide. P. ramorum was isolated from the following C. oleifera cultivar on two or more occasions: Winter's Fire.
Disease Control Outlines
Camellia (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
CARNATION
Dianthus caryophyllus (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Alternaria leaf spot* and
branch rot
(Alternaria saponariae)
Gray-brown leaf or petal spots with purple margins. Black
spore masses form in spots. Branch rot starts at nodes
and girdles stem.
In infected plants and debris. Airborne spores. Moist conditions for 8 to 10 hours required for infection.
Provide good air circulation and keep humidity low. Irrigate in
early morning. Do not wet foliage with irrigation water. During
periods of high humidity, protect plants with iprodione, mancozeb, or chlorothalonil.
Bacterial wilt*
(Pseudomonas caryophylli)
Sudden wilting of tops or individual branches. Basal stem
cracks. Roots may be rotted. Vascular discoloration in
stems is yellowish to brown. The outer layer (epidermis)
separates easily from stem, which is sticky to the touch.
Infected plants and debris. Bacteria spread in water. Favored by high temperatures.
Use disease-free cuttings and treat soil as above. Bacteria can
spread quickly. Avoid use of cutting dips and avoid splashing
water. Break cuttings from stock plants. Disinfect tools.
Calyx rot
(Stemphylium botryosum)
Rot starts at tip of calyx and progresses towards base.
In old leaves, stems, and debris. Favored by high humidity.
Same as Greasy blotch. Harvest regularly.
Fairy-ring leaf spot
(Cladosporium echinulatum)
Conspicuous tan spots with concentric rings. Margin of
spot may be red. Dark spores form in spots.
Infected plants and debris. Airborne spores. Favored by
wet weather.
Provide good air circulation and keep humidity low. Irrigate in
early morning. Do not wet foliage with irrigation water. Protect
foliage with mancozeb.
Fusarium bud rot
(Fusarium tricinctum)
Outwardly normal buds are brown and decayed inside.
Cottony white growth and plump white mites may be visible.
Fungus carried by grass mite, Pediculopsis graminum.
Destroy infected buds. Control mites. Do not bring field-grown
carnations into greenhouse. Control weeds outside growing
area.
Fusarium stem rot
(Fusarium avenaceum,
F. culmorum, F. graminearum)
Stem rotted at soil line and high up on plant. Roots and
base of stem rotted. Tops wilt and die. Pink cushions of
spores may form at base of plant on decayed tissues.
Common as a cutting rot.
In soil and plant debris. Spores spread in water. Also favored by warm, humid conditions. Also favored by high N
fertilization and high N:K ratio.
Use clean cuttings and rooting medium. Spray cuttings in rooting medium with thiophanate-methyl.
Fusarium wilt*
(Fusarium oxysporum f. sp.
dianthi)
Yellow, wilted branches frequently occur on one side at
first. Vascular discoloration is dark brown. Root system
usually remains intact. In late stages, stem develops a
dry, shredded rot. Infected parts die.
Soil and infected plants. Spores spread in water. Favored
by soil temperatures 75°F and above. Restricted below
60°F.
Plant resistant cultivars. Use disease-free cuttings planted in
treated soil. Steam soil in raised beds at 140°F for at least 30
minutes. Solarize soil or fumigate with chloropicrin. Adjust soil
pH to 6.5 to 7.0.
Moderately resistant:
Ace, Apache, Barsemi Yasmino, Big Red, Comanche, Corona, Exquisite Select, Felicia, Fiesta, Georgia Ann, Jolievette, Lucy Carrier, Maman, Mei-Sciang, Orchid Beauty, Pallas, Shiro,
Silvery Pink, Sweetheart, White Elegance
Highly resistant:
Barbi, Candy Maj, Capello, Carbasio, Improved Lilac, Juanita, Lady Di, Light Pink Marble, Maiko, Maj Pink, Meiling, Melody, Moonlight, Picotee Orange, Scarlett Elegance, Siri #1, White
Melody
Gray mold*
(Botrytis cinerea)
Fuzzy gray fungal spores form on soft, brown, decayed
blossoms and can move into plant parts wherever blossoms touch them.
In plant debris. Airborne spores. Favored by high moisture conditions and low temperatures.
Remove old flowers from growing area. Maintain horizontal air
movement. Lower humidity where possible. Mist blooms with
iprodione or fenhexamid.
Continued on next page . . .
Disease Control Outlines
Carnation (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Carnation, continued
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Greasy blotch
(Zygophiala jamaicensis)
Greasy-appearing spots on leaves with radiating weblike
margins. Pimpling of infected areas.
In infected plants and debris. Favored by high humidity.
Not too common.
Provide good air circulation and keep humidity low. Irrigate in
early morning. Do not wet foliage with irrigation water.
Phialophora wilt
(Phialophora cinerescens)
Gradual wilting of plants; leaves become straw colored.
Not one-sided as Fusarium wilt may be. Brown discoloration of vascular system. Little or no tissue rotting in late
stages. Uncommon.
Soil and infected plants. Spores spread in water. Favored
by cool soil temperatures.
Use disease-free cuttings and treat soil as above.
Phytophthora stem rot*
(Phytophthora parasitica)
Stem rotted at soil line. May be mistaken for Rhizoctonia
stem rot.
In soil and plant debris. Favored by warm, moist soil and
poor drainage.
Steam or fumigate soil. Drench at planting with oomycete (water mold) specific fungicide.
Pythium root rot*
(Pythium spp.)
Plants are stunted, particularly in lower, poorly drained areas. Rootlets rotted.
Soilborne. Common in most soils. Favored by poor drainage, low spots, excessive irrigation.
Steam or fumigate soil (see Fusarium wilt). Drench plants with
oomycete (water mold) specific fungicide periodically, depending on severity of disease. Make first application at planting.
Rhizoctonia stem rot
(Rhizoctonia solani)
Stem rotted at soil line. Rot progresses from the outside.
Entire plant wilts and dies. Dark fungal strands and sclerotia may be visible with a hand lens.
Soilborne; plant debris. Favored by warm, moist conditions.
Steam rooting medium and soil. Use PCNB before transplanting, or spray base of transplant with iprodione.
Rust*
(Uromyces dianthi)
Small pustules of powdery brown spores. Spores are airborne.
Carried over only on living plants. Favored by moist conditions.
Use resistant cultivars or protect plants in problem areas with
myclobutanil or mancozeb.
Virus or viruslike diseases
Symptoms
Host range and natural spread
Comments on control
Mottle
Faint leaf mottle or no symptoms. Common in virtually all
carnation cultivars.
Handling and cutting knife. Not transmitted by insects.
May be spread in drainage water.
Reduce spread of mottle by disinfecting tools between blocks
of plants and several times a day. Obtain virus-free plants.
Etched ring
Rings usually oval or elongated; rarely concentric on
older leaves and stems. Symptoms may be slight in
young cuttings. No obvious effect on plant vigor.
Aphids. Not spread by handling.
Obtain virus-free plants. Control aphids.
Necrotic fleck
Reddish purple necrotic flecks, streaks, or spots appear
in leaves. Symptoms are masked at low temperatures.
Aphids.
Obtain virus-free plants. Control aphids.
Ring spot
Small 0.5- to 1-inch rings; sometimes concentric. Chlorosis, mottling, and distortion of young leaves. Plants obviously stunted.
Cutting knife and handling. Insect vectors unknown.
Same as for mottle.
Vein mottle
(not common in California)
Young leaves exhibit a vein clearing, which develops into
chlorotic spots and patterns that mostly follow veins.
Symptoms tend to disappear on old leaves.
Aphids. Not spread by handling or cutting knife.
Obtain virus-free plants. Control aphids.
(Carnation mottle virus)
* For additional information, see section on Key Diseases.
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CATTLEYA
Cattleya spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial soft rot
(Dickeya (=Erwinia) chrysanthemi)
Soft, watery rot of leaves; often foul smelling. Starts as
small water-soaked area. Infection is through wounds. Often kills cattleya plants.
In soil and decaying plant debris. Bacteria spread in water. Favored by warm, moist conditions.
Avoid overhead watering, wounding plants, and provide horizontal air movement and good aeration. Observe strict sanitation. Disinfect knives between cuts.
Black rot and seedling
damping-off (Pythium ultimum*,
Phytophthora cactorum*)
Starts as small, water-soaked leaf spots and root rot. Decay may progress rapidly. Affected tissues turn black and
are sometimes soft.
Soilborne fungi. Spores spread in water. Favored by
warm moist conditions (above 65°F).
Drench plants with oomycete (water mold) specific fungicide.
Steam or chemically treat growing media and used pots. Remove badly infected plants.
Botrytis flower brown speck or
rot
(Botrytis cinerea)
Tiny, light-brown spots on blossoms may enlarge to rot
entire flower. Fuzzy gray fungal spores develop on flowers if kept moist.
On plant debris. Spores airborne. Favored by cool, moist
conditions.
Eliminate old flowers. Eliminate plant debris, both inside and
outside growing area. Avoid getting flowers wet. Treat with
fenhexamid.
Gloeosporium leaf spot
(Gloeosporium spp.)
Prominent, sunken, reddish brown spots with definite
margins. Spots may coalesce and kill entire leaf. Spots
start as minute, dark areas, often at leaf tips.
In infected plants. Spores spread in water. Favored by
moist conditions and unfavorable growing conditions.
Provide better growing conditions. Avoid wetting foliage. Remove infected tissues.
Rust
(Sphenospora kevorkianii,
Uredo nigropuncta)
Pustules of powdery, yellow or orange spores on undersides of leaves.
In infected plants. Spores airborne. Moisture needed for
only short period. Not too common.
Avoid wetting leaves. Destroy infected leaves.
Virus or viruslike disease
Symptoms
Natural spread and host range
Comments on control
Blossom necrotic streak
(a strain of Cymbidium mosaic
virus)
Blossoms open without evidence of brown spots or
streaks, which become visible after about 1 week or
longer. Long, yellowish, irregular streaks may develop on
leaves.
Can be spread on cutting tools.
Use clean cutting tools. Destroy infected plants.
Leaf necrosis
(Cymbidium mosaic virus)
Irregular, elongated streaks of dead tissue on undersurface of older leaves. Some leaves may be killed or various patterns of sunken, black tissue may develop. Infected plants may show no symptoms.
Spread by pruning tools. Cattleya and its hybrids, Cymbidium, Epidendrum, Zygopetalum, Angraceum, Laelia,
Oncidium, Spathoglottis.
Use clean and disinfected cutting tools.
Mild flower break
(Odontoglossum ringspot virus)
Flowers less variegated than above and without distortion. Leaves show only mild, hard-to-detect mosaic symptoms. Spots and streaks of increased pigment intensity.
Unknown, but can be transmitted by juice inoculations.
Cattleya and its hybrids, Cymbidium, Odontoglossum,
Phalaenopsis.
Isolate or destroy infected plants. Disinfect tools between cuts
with a quaternary ammonium disinfectant.
Severe flower break
Variegation of flower color. May also distort sepals and
petals. Leaves mottled with streaks of light and dark
green tissue. Dark green areas somewhat raised, producing ridges and bumps.
Spread by green peach aphid. Cattleya and its hybrids,
Cymbidium.
Same control for all viruses.
Virus or viruslike disease
Symptoms
Natural spread and host range
Comments on control
Symmetrical flower break
A symmetrical variegation in which pigment occurs along
sepal margins and over most of petals, except in middle
Unknown, but can be transmitted by juice inoculations.
Cattleya.
Use clean and disinfected cutting tools.
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areas that have little or no pigment. Leaves may develop
an inconspicuous mosaic mottle.
* For additional information, see section on Key Diseases.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
CHRYSANTHEMUM
Chrysanthemum grandiflora (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial blight*
(Dickeya chrysanthemi)
Water-soaked lesions; pith becomes jellylike; tops turn
black and exude drops of liquid. Stem may break or split.
In plant debris. Favored by high temperatures (80° to
90°F), absence of free water, and high humidity.
Use disease-free cuttings. Reduce humidity in growing areas.
Dip cuttings in streptomycin.
Cottony rot*
(Sclerotinia sclerotiorum)
Stems rotted; flower rot is similar to gray mold. Cottony,
white fungal mass may occur on rotted tissues. Black
sclerotia may form inside or outside stems.
Sclerotia in soil. Spores produced from sclerotia are airborne but infect only through flowers and dead tissues.
Favored by high humidity.
Same as for gray mold. Also, treat soil with PCNB before
planting and spray foliage with iprodione or thiophanate-methyl.
Crown gall
(Agrobacterium tumefaciens)
Irregular or round galls on stems and sometimes leaves.
Soil and galls. Infection favored by moist conditions.
Destroy infected plants.
Foliar nematode
(Aphelenchoides ritzemabosi)
Dark green, angular spots in leaves develop progressively upward from base of plant. Leaves turn yellow.
These nematodes are rarely important in California.
Adults can survive up to 3 years in dead leaves. Spread
by splashing water. Leaves need to be wet for infection to
take place.
Use disease-free plants. Discard infected plants. Avoid overhead irrigation. Control weeds. Submerge infected plants in
hot water (115°F) for 10 minutes.**
Fusarium wilt*
(Fusarium oxysporum
f. sp. chrysanthemi and f. sp.
tracheiphilum)
Unilateral chlorosis of one or more leaves near the apex,
followed by curvature of the stem towards the affected
side. As the disease progresses, there is a general chlorosis and wilt and stunting of leaves. The vascular system
becomes a reddish brown.
Soilborne and carried in cuttings. Favored by high soil
temperatures (80°F).
Use disease-free cuttings in clean soil. Treat soil (see Verticillium wilt). Adjust pH of soil to 6.5 to 7.0 and use nitrate nitrogen. Avoid planting highly susceptible cultivars (Bravo, Cirbronze, Illini Trophy, Orange Bowl, Royal Trophy, Yellow Delaware)
Gray mold*
(Botrytis cinerea)
Brown, water-soaked spots on petals. Fuzzy gray fungal
spores form on decayed tissues. Rotting of lower leaves.
Fungus may enter and girdle stem.
In plant debris. Favored by high humidity, low temperatures (50° to 60°F), and water on plant.
Keep humidity low; avoid overhead irrigation. Protect foliage
with a fungicide, especially lower-dense foliage. Mist blooms
with chlorothalonil, iprodione, or fenhexamid.
Hollow stem
(Pectobacterium (=Erwinia) carotovorum)
Pith of rooting cuttings deteriorates and collapses. Affected tissues are brown. Surviving plants do not grow
satisfactorily and pith collapse may extend upward involving several internodes. Red Torch, Tempo, and Tempter
are very susceptible cultivars.
Bacteria may be present in vascular bundles of symptomless chrysanthemums. Bacteria also present in undecomposed debris. Favored by high temperatures and high
moisture.
Use disease-free cuttings. Reduce humidity in growing areas.
Streptomycin dips may be helpful.
Powdery mildew*
(Golovinomyces cichoracearum)
White powdery growth on leaves and stems. Found
mainly on older leaves.
Airborne spores produced only on living plants. Favored
by high humidity, crowding of plants, and cool weather.
Spray with piperalin to eradicate existing infections. Protect
foliage with myclobutanil or triadimefon.
Pythium root rot and basal
stem rot*
(Pythium spp.)
Girdling black lesions occur near soil line. Plants stunted
because of reduced root system caused by root rot.
Plants may die.
Soilborne pathogen. Spores spread in water or in soil. Favored by excess soil moisture and poor drainage.
Treat soil as for Verticillium wilt. Drench plants with oomycete
(water mold) specific fungicide.
Ray blight
(Phoma chrysanthemi)
Basal leaf and stem rot. Below ground stem infection may
cause a one-sided distortion and necrosis of foliage.
Blackish rot of petals (ray blight) may extend into flower
stalk.
In chrysanthemum refuse. Waterborne spores. Favored
by rainy weather.
Use disease-free cuttings. Avoid wetting foliage and keep humidity low. Protect foliage with chlorothalonil.
Continued on next page . . .
Disease Control Outlines
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Chrysanthemum, continued
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Rhizoctonia stem rot
(Rhizoctonia solani)
Stem rotted at soil line. Plants stunted. Dark fungal
strands may be visible with hand lens. May kill plants.
Soilborne fungus. Favored by warm, moist conditions.
Avoid deep planting. Spray base of transplants with thiophanate-methyl, chlorothalonil, or iprodione after planting, or treat
soil with PCNB before planting.
Rust*
(Puccinia tanaceti)
Small pustules of powdery, chocolate-brown spores on
undersides of leaves and on stems.
Airborne spores produced only on living plants. Free
moisture necessary for infection. Principally a field disease.
Use resistant cultivars. Protect foliage with triadimefon or
mancozeb before rust starts to build up. Avoid wetting foliage. Keep humidity low.
Septoria leafspot
(Septoria obesa, S. chrysanthemi)
Irregular or circular, brown or black dead spots develop
progressively upward from base of plant. Tiny black fungal fruiting bodies in centers of spots.
In plant debris and in soil debris for 2 years. Spores
spread in splashing water. Favored by wet weather.
Protect foliage with a fungicide at first sign of disease. Greenhouse: avoid wetting foliage. Keep humidity low.
Verticillium wilt*
(Verticillium dahliae)
Yellowing and wilting of foliage, may be one-sided.
Leaves die and dry upward from the base of the plant.
Vascular tissue may be discolored.
Soilborne for many years. Carried in cuttings and root divisions. Favored by cool weather followed by hot weather
during flowering.
Use resistant cultivars and pathogen-free plants. Fumigate
with chloropicrin or other chloropicrin combinations. In sunny
climates, soil solarization might be considered.
White rust
(Puccinia horiana)
Whitish pustules on the lower leaf surface. On the upper
surface the infection is evident as pale-green to yellow
spots up to 4 mm in diameter. Raised, waxy, pink-colored
pustules are formed on lower leaf surface and can coalesce into large areas covering the leaf, Pustules found
on stems and sometimes flowers. As they mature and
produce spores, they turn whitish in color.
This microcyclic rust survives on living chrysanthemum
foliage. Teliospores in the leaf pustules germinate in
place producing basidiospores that are airborne and infect by direct penetration. Favored by the same conditions as ordinary rust (cool, damp weather), except that
direct sunlight destroys airborne basidiospores. Principally a greenhouse disease.
White rust is widespread throughout many areas of the world
but is not confirmed as established in the United States. Any
offshore introduction of this pathogen is a significant threat to
the United States floriculture industry. It spreads rapidly in
greenhouse and nursery environments, resulting in severe
losses. As a quarantine pest, detection leads to federal and
state regulatory action. See USDA Plant Pest Program for
Chrysanthemum White Rust.
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Disease Control Outlines
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Chrysanthemum, continued
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Aspermy
(Tomato aspermy virus)
Flower distortion and reduction in flower size. Color break
in florets of red, bronze, and pink cultivars. Foliar symptoms not apparent. Some cultivars are symptomless.
Transmitted by handling, cutting tools, and vegetative
propagation. Also transmitted by aphids.
Use disease-free cuttings. Control aphids; remove infected
plants.
Chlorotic mottle
(Chrysanthemum chlorotic
mottle viroid)
Mottling followed by complete chlorosis. May be confused
with nutritional problems. Symptoms somewhat masked
under low light and cool temperature conditions below
70°F.
Spread by handling, cutting tools, and vegetative propagation.
Use disease-free cuttings. Remove infected plants.
Spotted wilt
(Tomato spotted wilt virus, Impatiens necrotic spot virus)
Frequently one-sided in plant. Ring patterns on leaves of
some cultivars. Leaf distortion and necrosis. Dark necrotic
streaks on stems. Flowers may be distorted and with
some necrosis.
Thrips-transmitted; not spread by cutting knife, but can be
spread by vegetative propagation. Many weeds and perennial ornamental plants act as reservoirs of virus (dahlia,
calla, nasturtium, mallow, knotweed, plantain, and others).
Eliminate nearby susceptible ornamental plants and weeds.
Control thrips inside and outside growing areas. Use virus-free cuttings.
Stunt
(Chrysanthemum stunt viroid)
General stunting of plants. Foliage may be pale with upright, young leaves. Flowers are smaller than normal and
some cultivars may flower 7 to 10 days early.
Viroid is easily transmitted by handling, cutting knives,
vegetative propagation, etc. Not spread by insects. Viroid
has a wide host range. Symptomless in some plants.
Obtain disease-free plants from a propagation specialist using an indexing program.
Chrysanthemums are also susceptible to Ascochyta blight (Mycosphaerella ligulicola, Ascochyta chrysanthemi), aster yellows* (aster yellows phytoplasma), charcoal rot (Macrophomina phaseolina), and southern blight* (Sclerotium rolfsii).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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CYCLAMEN
Cyclamen spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Anthracnose
(Cryptocline [=Gloeosporium]
cyclaminis)
Distinctly zonate, pale green and circular spots. Orange
to pink-colored spores on stems and leaves.
Gray mold*
(Botrytis cinerea)
Spotting of flowers. Decay of emerging flower stems
and leaf petioles under leaf canopy. Fuzzy gray fungal
spores form on rotted tissues.
In plant debris, especially flowers. Common saprophytic
fungus. Favored by cool, wet weather. Water necessary for
spore germination.
Avoid overhead watering. Remove old flowers. Improve air
circulation. Control humidity to avoid moisture condensation.
Treat with iprodione or fenhexamid.
Soft rot
(Dickeya (=Erwinia) chrysanthemi)
Plants collapse suddenly. Tuber is mushy.
Infected plants and debris. Disease is favored by high temperatures (75°F and above). Bacteria are spread by splashing water and handling.
Discard infected plants. Avoid excessive water splashing.
Maintain sanitary conditions. Keep greenhouse cool.
Root rot
(Pythium* and Phytophthora
spp.*)
Plants are stunted. Roots are discolored and rotten,
lower leaves wilt and may turn yellow.
Pathogens are normal inhabitants of natural soil. Disease is
favored by poor drainage and overwatering.
Heat-treat growing medium at 140°F for 30 minutes or fumigate. Drench plants with oomycete (water mold) specific fungicide.
Fusarium wilt*
(Fusarium oxysporum f. sp.
cyclaminis)
A progressive yellowing and wilting of leaves starts with
oldest. Brown discoloration of the vascular tissues in tubers. Tuber remains firm unless secondary bacteria are
introduced.
Survives as resting spores (chlamydospores) in soil. No
other plants are infected. Disease is favored by temperatures above 70°F. May be seedborne.
Discard infected plants and soil; don't save seed from infected plants. Good sanitation generally provides adequate
control. Thiophanate-methyl drenches during early growth
period should be helpful. Adjust soil pH to 6.5 to 7.0. Treat
seed with a fungicide.
Leaf spots*
(Phyllosticta cyclaminis)
Yellowish-to-brownish spots near leaf margins.
On diseased plants and plant debris. Favored by wet conditions. Dissemination of spores is by splashing water.
Control is same as for gray mold. Protect foliage with a fungicide.
Septoria leaf spot
(Septoria cyclaminis)
Red concentric spots turn gray with red borders.
Stunt
(Ramularia cyclamanicola)
Conspicuous stunt. Flower peduncles shortened so that
flowers open below surrounding leaves. Reddish brown
necrosis in tuber. Brown irregular leaf spots. Frosty appearance on underside of lower yellowed leaves.
Infected plants and debris. Spores are airborne. Favored by
warm, moist conditions.
Dispose of infected plants, keep humidity low. Keep seedlings away from older plants. Protect plants with thiophanatemethyl.
Cyclamen are also susceptible to black root rot (Thielaviopsis basicola) and Cylindrocladiella disease (Cylindrocladiella peruviana).
* For additional information, see section on Key Diseases.
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CYMBIDIUM ORCHID
Cymbidium spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Black rot*
(Pythium ultimum)
Rapid, black rot of pseudobulb and rotting of roots.
Bulb, usually firm at first, gradually desiccates, forming
a hard mummy.
Soilborne pathogen. Spores spread in water. Favored by
poor drainage and excess water.
Provide better drainage. Avoid excess irrigation. Drench plants
with oomycete (water mold) specific fungicide. Steam or chemically treat growing medium.
Flower spotting
(Botrytis cinerea)
Small black, brown, or colorless spots often surrounded
by water-soaked areas.
In plant debris. Spores airborne. Favored by cool (45° to
60°F), moist conditions and condensed moisture on flowers.
Avoid wetting flowers. Keep humidity as low as possible. Eliminate old flowers and plant debris both inside and outside growing area.
Sclerotium or collar rot
(Sclerotium rolfsii)
Rapid rotting and collapse of the leaf bases and stem.
White fungus growth and small resting structures (sclerotia) that resemble mustard seeds usually present on
plant and planting medium.
Sclerotia survive in soil for many years. No spores form.
Favored by warm, moist soil. Fungus has a wide host
range.
Destroy infected plants. Heat-treat soil, fumigate with chloropicrin or another chloropicrin combination, or mix granular PCNB
with planting medium before planting.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Bar mottle
(Cattleya severe flower break virus)
Yellow bar-shaped streaks and blotches on leaves.
Green peach aphid. Cymbidium, Cattleya, and its hybrids.
Same as for mosaic. Also, control insects.
Diamond mottle
(Odontoglossum ringspot virus)
(Tobacco mosaic virus, orchid
strain)
Elongated chlorotic areas are sometimes diamondshaped. Older leaves sometimes develop
brown-to-black flecks and streaks.
Can be transmitted by juice inoculations. Cymbidium, Cattleya, Odontoglossum, Phalaenopsis.
Same as for mosaic.
Mosaic
(Cymbidium mosaic virus)
Symptoms vary in pattern and severity. Small, elongate
pale areas in young leaves may later develop into dead,
dark spots or streaks. Mottling of young leaves, sometimes becomes inconspicuous in old leaves. No flower
variegation.
Transmitted by pruning tools. Cymbidium, Cattleya, Epidendrum, Zygopetalum, Angraceum, Laelia, Oncidium,
Spathoglottis.
All virus diseases are propagated with plant. Once infected,
plant remains so for life. Destroy infected plants. Disinfect tools
between cuts or heat-sterilize in a flame.
Ringspot virus
(Cymbidium ringspot virus)
Necrotic ringspot patterns on young and old leaves.
Plants severely stunted. Can be lethal.
Can be transmitted by juice inoculations. Cymbidium, Cattleya, Spathoglottis, Trichosoma.
Same as for mosaic.
* For additional information, see section on Key Diseases.
Disease Control Outlines
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DAHLIA
Dahlia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Crown gall*
(Agrobacterium tumefaciens)
Overgrowths or galls occur on stems and roots.
In soil for as long as 3 years; bacteria enter through
wounds and can survive on infected roots. Gall development favored by rapidly growing host.
Avoid wounding plants. Do not grow plants in infested soil for 3
years, or fumigate soil. Discard infected roots. Rotate with
non-woody crops, such as cereals and legumes.
Fusarium wilt*
(Fusarium oxysporum)
Symptoms are almost identical to those of Verticillium
wilt. Not common in California.
Soilborne for many years. Disease most severe when soil
temperatures are high.
Destroy infected plants. Grow plants in new areas or fumigate
soil; see below for control of Verticillium wilt.
Gray mold*
(Botrytis cinerea)
Brown, water-soaked spots appear on petals. Fuzzy
gray fungus spores form on soft, brown, decayed tissues; fungus may invade plant tissue that touches infected petals.
Plant debris. Favored by cool, wet conditions and condensed moisture on plants.
Remove withered or diseased flowers promptly. During cool,
wet weather, spray with iprodione, mancozeb, or fenhexamid.
Powdery mildew*
(Golovinomyces cichoracearum)
White, powdery fungus principally grows on older
leaves and stems. Severely affected leaves dry up and
may fall.
On living dahlia leaves and as small, dark, resting structures (chasmothecia) on old leaves. Free water is not necessary for infection.
Protect foliage with myclobutanil or sulfur.
Root knot nematode**
(Meloidogyne spp.)
Knots or small swellings, caused by root knot nematodes, occur on feeder and fleshy roots.
In soil and on the roots of many plants. Favored by warm,
sandy soils.
Use a nematicide to treat infested soil before planting or solarize soil. Destroy infected roots.
Sclerotinia or cottony rot*
(Sclerotinia sclerotiorum)
Plants wilt and die suddenly. Water-soaked stem cankers appear near the soil line. Cottony, white fungal
growth; later, large black sclerotia are found on insides
and outsides of stems.
In soil as sclerotia, which produce airborne spores that infect only inactive or weak tissues. Sclerotia also produce
hyphae, which infect plant tissue. Favored by cool, moist
conditions.
Avoid soil where disease has occurred (common disease of
many vegetable crops). Treat soil with PCNB before planting.
Protect plants with iprodione or thiophanate-methyl.
Smut
(Entyloma dahliae)
Yellowish, circular to irregular spots appear on leaves.
Leaves later become brown and dry.
Plant debris. Favored by wet weather.
Do not use overhead irrigation. Mancozeb applied to control
gray mold should help control smut.
Storage rots
(Botrytis cinerea, Pectobacterium (=Erwinia) carotovorum,
Fusarium spp.)
Roots rot in storage.
Plant debris. Favored by high temperature and humidity.
Avoid plant injuries. Maintain a storage temperature of 40°F
and avoid high humidity. In mild climates, leave roots in soil.
Verticillium wilt*
(Verticillium dahliae)
Basal leaves wilt and turn yellow. Frequently, only one
branch is affected at first. Later, the entire plant dies.
Dark discoloration of the vascular system occurs.
In soil for many years. Symptoms most severe during
warm weather after a cool period. Fungus has a wide host
range.
Destroy infected plants and roots. Fumigate soil with chloropicrin or a chloropicrin combination (tarped). Fumigation also controls most other fungi, bacteria, weeds, nematodes, and soil insects. Soil solarization might be considered in sunny climates.
Continued on next page . . .
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Dahlia, continued
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Dahlia mosaic
(Dahlia mosaic virus)
The normal green color of leaves develops irregularly.
Bands adjacent to the veins remain pale green
(vein-clearing). Leaves may be distorted. Shortening of
internodes (stunt) occurs in some cultivars. Flower color
is usually normal.
Aphids. Spread vegetatively by cuttings and roots. In
some cultivars, the virus is almost symptomless.
Destroy infected plants. Control aphids.
Mosaic
(Cucumber mosaic virus)
Mild leaf mottle accompanied by little or no leaf distortion. Some varieties are symptomless carriers of the virus. Not common in California.
Aphids. Spread vegetatively by cuttings and roots. Many
plants: cucurbits, tomato, pepper, legumes.
Destroy infected plants. Control aphids and weeds.
Ringspot
(Tomato spotted wilt virus)
A well-defined mosaic mottle or irregular concentric
rings or wavy lines in leaves. No leaf distortion or stunting occurs. Symptoms seen on older leaves.
Thrips. Spread vegetatively by cuttings and roots. Many
plants.
Eliminate reservoir hosts and weeds. Destroy infected plants.
Control thrips. Eliminate virus by taking small, stem-tip cuttings
from rapidly growing plants.
Dahlias are also susceptible to southern blight* (Sclerotium rolfsii) and foliar nematodes (Aphelenchoides spp.).**
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
DELPHINIUM
Delphinium spp. and hybrids (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Black leaf spot*
(Pseudomonas syringae pv. delphinii)
Irregular, tarlike, black spots in leaves. Petioles and
stems also infected. Spots viewed from lower leaf surface appear brown.
Bacteria survive in plant debris from previous delphinium
crop. Disease is favored by cool, wet weather. Bacteria
are spread in splashing water.
Rotate field to a different crop. In perennial plantings, remove
old leaves and stems from field. Avoid overhead irrigation.
Diplodina disease
(Diplodina delphinii)
Brown to black stem cankers often at stem bases of
older plants. Basal canker may girdle the stem, causing
the tops to die and break over. Tiny, black fungus fruiting structures (pycnidia) may be visible in necrotic tissues. Uncommon.
Fungus survives on delphinium debris and in crowns of living plants. Spores are spread in splashing water.
Avoid overhead irrigation. Plant on raised beds. Do not replant
fields for 2 or more years. In perennial plantings remove old
stems and plant debris. Protective fungicidal sprays would
probably be effective.
Downy mildew*
(Peronospora spp., Plasmopara
spp.)
Purplish red to dark brown, irregular angular spots on
leaves. Lower surface covered with sparse, downy fungal growth that may be hard to see. Leaves turn yellow
and fall.
Spores produced only on living plants. Resistant spores
(oospores) carry fungus over unfavorable periods. Moist,
humid conditions.
Protect foliage with mancozeb, fosetyl-Al, dimethomorph, or
mefenoxam.
Powdery mildew*
(Erysiphe aquilegiae and Podosphaera delphinii)
White powdery patches on surface of leaves and
stems. Basal leaves yellow, then brown and die. Flowers may be deformed. Larkspur is particularly susceptible.
Fungus survives on living plants. Spores are airborne. Disease is favored by moderate temperatures, shade, crowding, and dry foliage.
Avoid overcrowding. Protect foliage with a powdery mildew
fungicide.
Soft crown rot and black leg
(Pectobacterium (=Erwinia)
atrosepticum)
Stem bases are blackened and rotted, causing stems to
fall over. New shoots may develop disease free under
drying conditions or entire crown may rot. Rotted tissues usually have an offensive odor. Disease often appears at time of flowering.
Favored by warm, wet conditions. Bacteria survive in plant
debris. Seeds may be contaminated by bacteria. Infection
is through normal stem cracks and wounds. Bacteria are
spread in water.
Avoid overhead irrigation, especially after flower spikes begin
to elongate. Plant on raised beds and avoid wetting crowns.
Heat treat or fumigate soil used to produce seedlings.
Water mold root rots
(Pythium* and Phytophthora
spp.*)
Plants are stunted and yellow. Roots rotted. When Phytophthora spp. are involved, crown tissues may be rotted. Lower stems are sometimes infected.
Pathogens are soilborne and present in most agricultural
soils. Spores (zoospores) are spread in water. Favored by
wet weather, poor drainage, and overwatering.
Improve drainage. Grow on raised beds. Do not overirrigate.
Fungicides used to control Pythium and Phytophthora should
be useful.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Aster yellows*
(Aster yellows phytoplasma)
Flowers are converted to green leafy structures. Plants
infected the preceding year produce many spindly, upright yellow shoots and no flowers.
Phytoplasma that has a wide host range and is spread by
leafhoppers. Not spread by seed, other insects, or handling.
Do not plant seed beds downwind from delphinium, carrot, or
celery fields. Control leafhoppers. Eliminate nearby weeds.
Destroy infected plants.
Delphiniums are also susceptible to gray mold* (Botrytis cinerea), southern blight* (Sclerotium rolfsii), cottony rot* (Sclerotinia sclerotiorum), root knot nematode** (Meloidogyne spp.), Verticillium wilt* (Verticillium dahliae), damping-off* (Rhizoctonia
solani, Pythium spp.), curly top (Beet curly top virus), various virus diseases (Tobacco mosaic virus, Radish mosaic virus, Cucumber mosaic virus), leaf spots (Ascochyta aquilegiae, Cercospora delphinii, Ramularia delphinii), white smut (Entyloma
winteri), rust* (Puccinia delphinii), and Fusarium wilt* (Fusarium oxysporum f. sp. delphinii).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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EASTER LILY
Lilium longiflorum (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Botrytis blight
(Botrytis elliptica, B. cinerea)
Circular or oval orange or reddish brown spots usually
appear on older leaves. Under damp conditions, fuzzy
gray fungal spores form on spots. Brown spotting of
blooms occurs. Botrytis elliptica infects healthy tissue
whereas B. cinerea invades only dead or dying tissue.
In plant debris. Spores are airborne. Favored by cool, wet
conditions and condensed moisture on plant parts.
Keep humidity below 85% by heating and ventilation. Do not
use overhead irrigation. Mist blooms and foliage with iprodione,
mancozeb, or fenhexamid.
Bulb rots
(Rhizopus spp., Penicillium spp.)
Bulb rot may be soft and mushy (Rhizopus spp.) or dry
and rotted (Penicillium spp.)
In plant debris. Spores are airborne. Favored by warm
storage temperatures.
Do not injure bulbs. Store bulbs under cool and dry conditions.
Thiabendazole bulb dips usually prevents Penicillium decay.
Fusarium bulb rot
(Fusarium oxysporum f. sp. lilii)
Lower leaves become yellow or purple and die. Plants
are stunted and of poor quality. Brown basal rot of bulb
occurs, causing the scales to fall off.
In diseased bulbs and soil. Favored by warm temperatures.
Do not plant bulbs that show any signs of infection. Dip bulbs in
thiabendazole. Plant deep in pot to force stem roots.
Leaf scorch
(nonparasitic)
Semicircular brown areas develop along leaf margins.
Leaf tips turn brown.
Most severe in high-acid and low-fertility soils.
Adjust soil pH to 6.5 or 7.0. Maintain adequate levels of nitrogen and calcium.
Root rots*
(Pythium spp., Rhizoctonia
solani)
Roots turn brown and rot. Plants are stunted with yellowing of lower leaves and leaf scorch. Buds are blasted, resulting in a reduced bud count.
In soil and on bulbs. Favored by overwatering and poor
drainage.
Drench plants with mefenoxam in combination with thiophanate-methyl. Mefenoxam at high rates may cause yellowing of
leaf margins of Easter lilies.
Shoot rot
(Phytophthora cactorum)
Growing points of emerging plants are rotted. Stems of
older plants are rotted, causing the plants to wilt and collapse. Roots are also frequently rotted.
Soilborne. Spores are spread in water. Favored by poorly
drained soil and overwatering.
Steam or chemically treat soil. Oomycete (water mold) specific
fungicide drenches also help control the fungus. (See root rot
control, above.)
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Fleck
(Cucumber mosaic virus and Lily
symptomless virus)
Small, brown, elongated spots appear parallel to leaf
veins mostly on older leaves. Flowers are smaller and
fewer than on healthy plant
Many hosts; transmitted by aphids.
Remove infected plants and control aphids.
Mosaic
(Tulip breaking virus)
Foliage shows a slight, dark and light green mottling.
Plants are usually salable.
Spread by aphids.
Obtain virus-free bulbs, if possible. Control aphids. Destroy infected plants. Root rot is more severe on virus-infected plants.
Rosette
(Lily rosette virus)
Leaves curl downward and are flat. Internodes are shortened, giving plants a flat rosette or cylindrical appearance in contrast to pyramid shape of a healthy plant.
Flowers fail to open correctly.
Symptoms tend to be masked at high temperatures
(above 75°F).
Easter Lilies are also susceptible to foliar nematodes (Aphelenchoides olesistis)** that cause bunchy top and black scale rot (Colletotrichum lilii).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
FUCHSIA
Fuchsia spp. (11/20)
Disease (causal agent)
Fuchsia rust*
(Pucciniastrum epilobii)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Initially, small brown areas appear on underside of
leaves. Later, large circular areas of chlorosis occur and
yellow-orange uredospores appear on the underside of
leaves. Older leaves may have green tissue around infected areas. Eventually uredospores appear on both
sides of leaf. Infected leaves usually drop.
Overwinters as teliospores on fireweed or as basidiospores on fir. Uredospores on fuchsia can reinfect fuchsia.
Remove fireweed and infected plants. Applications of mancozeb are effective. Avoid wetting leaves. Prune back to stems
and remove cuttings.
Fuchsias are also susceptible to crown gall* (Agrobacterium tumefaciens), Verticillium wilt (Verticillium dahliae), Armillaria root rot* (Armillaria mellea), damping-off* (Pythium rostratum, P. ultimum and Rhizoctonia sp.), Phytophthora root and crown
rots* (Phytophthora spp.), various viruses* (Tomato spotted wilt virus), eriophyid mites, and root knot nematodes** (Meloidogyne hapla).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
GERANIUM
Pelargonium spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Alternaria leaf spot*
(Alternaria tenuis)
Water-soaked areas occur on undersides of leaves.
Spots enlarge to 0.25 to 0.5 inch and have a slightly
sunken center surrounded by concentric rings of darker
brown or red tissue. Common on Pelargonium domesticum.
In plant debris and leaf spots. Favored by cool wet conditions.
Protect foliage with mancozeb. Iprodione sprays applied for
gray mold also may help.
Bacterial blight*
(Xanthomonas axonopodis pv.
pelargonii)
Round sunken leaf spots or angular dead areas appear
and are followed by wilting and death of leaf. Systemic
infection results in defoliation and frequently death of
plant. Infected stems are blackened and shriveled.
Black streaks may occur in nonrotted portions of stem.
Older plants may not exhibit symptoms.
In infected cuttings and plants and in plant debris in soil for 1
year. Disease develops rapidly at high temperatures. Bacteria are spread in water and can be vectored by greenhouse
whitefly from diseased to healthy geranium plants.
Use disease-free propagative material and observe strict sanitation. Steam or chemically treat rooting media. Disinfect cutting knives in a solution containing quaternary ammonia.
Avoid overhead irrigation.
Bacterial leaf spot
(Pseudomonas cichorii)
Dark brown to black, irregularly shaped spots (0.25 to 1
inch in diameter). Margins are water-soaked. Spots may
develop tan centers and have a yellow halo.
Infected plants. Many kinds of plants are susceptible. Favored by warm temperatures, rain, and overhead irrigation.
Avoid overhead irrigation. Maintain sanitation.
Blackleg and root rot*
(Pythium spp.)
Brown water-soaked bases of cuttings and young
plants. Lesions enlarge rapidly, move up the stem, and
turn black. Affected plants wilt and die.
Soilborne. Favored by overwatering and poor drainage.
Follow recommendations above. Drench plants with oomycete (water mold) specific fungicide. Remove and destroy infected plants.
Edema
(nonparasitic)
Small, water-soaked, pimplelike spots appear on undersides of leaves and stems. Spots later become corky.
Favored by cloudy, cool weather. Actual cause unknown.
Do not overwater. Keep humidity low. Maintain higher temperatures.
Gray mold*
(Botrytis cinerea)
Brown water-soaked decay of flowers occurs. Fuzzy
gray fungal spores form on rotted tissues. When infected flower parts fall on leaves, they also rot. Disease
may affect stems.
In plant debris, especially flowers. Favored by cool wet conditions and water on plant.
Protect plants with chlorothalonil, iprodione, or fenhexamid.
Where practical, remove old blossoms and dead parts. Avoid
overhead irrigation.
Rust*
(Puccinia pelargonii-zonalis)
Pustules of orange-brown spores form on undersides of
leaves.
On living leaves. Favored by moist conditions and water on
plants. Spores are airborne.
Protect foliage with triadimefon and myclobutanil. Lower humidity to avoid condensation of water on leaves. Mancozeb
also will help control rust.
Verticillium wilt*
(Verticillium dahliae)
Lower and middle leaves wilt, yellow, die, and fall.
Shoots die back. Plants are stunted. In later stages, water-conducting tissues (xylem) may be discolored.
Remains in soil for many years. Also spread by infected cuttings and plants. Fungus has wide host range (tomato,
strawberry, chrysanthemum, nightshade, and many others).
Favored by moderate temperatures. Symptoms most severe
in warm weather.
Use pathogen-free cuttings. Steam treat or fumigate soil with
chloropicrin or a chloropicrin combination. Avoid soil previously planted to tomatoes, strawberries, potatoes, chrysanthemums, or other susceptible crops.
Continued on next page . . .
Disease Control Outlines
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Geranium, continued
Virus or viruslike disease
Flower break
(Pelargonium flower break virus)
Leaf curl
(Pelargonium leaf curl virus)
Symptoms
Host range and natural spread
Comments on control
Symptoms vary depending on viruses present, cultivar,
and growing conditions. Symptoms include light and
dark green mottling of foliage, chlorotic spotting, ring
spotting, leaf distortions, leaf breaking, vein clearing,
and others.
In infected geranium plants. Symptoms of some are masked
during warm weather.
Obtain virus-free cuttings. Do not propagate from plants that
have shown symptoms of virus.
Line pattern
(Pelargonium line pattern virus)
Mosaic
(Cucumber mosaic virus)
Ringspot
(Tomato ringspot virus or Tobacco ringspot virus or both)
Geraniums are also susceptible to Armillaria root rot* (Armillaria mellea), crown gall* (Agrobacterium tumefaciens), bacterial fasciation (Rhodococcus fascians), and cottony rot* (Sclerotinia sclerotiorum).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
Geranium (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
GLADIOLUS
Gladiolus spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Botrytis disease* (Botrytis blight,
Neck rot, Corm disease)
(Botrytis gladiolorum, B. cinerea)
Tiny brown leaf spots develop; spots may expand or coalesce. Brown water-soaked spots appear on flower
petals. Basal stem infections (neck rot) may penetrate
corm; corm decay may continue in cold storage. Fuzzy
gray fungus spores may form on decayed tissues.
Black seedlike sclerotia may form on underground
parts.
In corms and on crop refuse. Spores are airborne. Favored by moist conditions and low temperatures (50° to
70°F).
Complete control program essential in coastal areas: cure and
treat corms as outlined at end of this section; protect foliage
with chlorothalonil, iprodione, mancozeb, or thiophanate-methyl. After harvest and before packing, spray flower spikes with
a fungicide.
Fusarium yellows
(Fusarium oxysporum f. sp.
gladioli)
Leaves tend to turn downward, yellow progressively,
and die prematurely. Brown rot of corms begins in basal
plate and core, and extends upward into the leaf bases
via vascular strands. Corms may rot in ground or while
in storage. Cultivars vary in symptoms and susceptibility. Infection without obvious symptoms is common.
In diseased corms and in infested soil for many years. Favored by temperatures of 70°F or above.
Plant disease-free corms in clean soil, or grow resistant cultivars. Hot water treatment of cormels eliminates the fungus
from infected stocks. Cure and treat corms as outlined at end
of this section. Fumigate infested soil with chloropicrin or a
chloropicrin combination. Disease is less severe if soil pH is
6.6 to 7.0 and 80 to 90% of nitrogen is the nitrate form.
Penicillium corm rot
(Penicillium gladioli)
A firm brown corm rot develops in storage; frequently in
association with other corm rots. If conditions are moist,
greenish blue spore masses appear over rotted areas.
On corms and corm debris and as spores on storage-room
equipment. Rot develops rapidly when humidity is high.
Cure and treat corms as outlined at end of this section.
Rhizoctonia neck rot
(Rhizoctonia solani)
Stem below ground and husks at harvest appear shredded. Brown fungus strands (mycelium) visible with a
hand lens.
Common soilborne fungus with wide host range. Favored
by warm, wet conditions.
Corm dips help control the fungus. Treat soil with PCNB before planting. Sprays of iprodione or thiophanate-methyl
should reduce spread of the fungus down the row.
Rust
(Uromyces transversalis)
First seen as small yellowish spots that later break out
of leaves, stems, and sometimes flowers, forming pustules with yellow-orange spores. May also include yellowish-brown (uredinia) or blackish-brown (telia) pustules.
Besides Gladiolus species, other hosts include other
members of the Iris family: Crocosmia, Tritonia, and Watsonia. Spores can contaminate corms, rhizomes and
bulbs. Spores can be blown long distances by wind.
Only accept corms and plants from known clean sources. Prevent introduction into nursery by careful regular monitoring.
Scab
(Pseudomonas gladioli pv. gladioli)
Mainly seen on corms as irregular or round sunken
brown spots with a shiny, brittle, varnishlike material
(bacterial exudate) on the surface.
On corms and in soil refuse for 2 years. Favored by heavy,
wet soils and warm weather. Encouraged by heavy nitrogen fertilization.
Rotate every 3 years. Control measures for other diseases
usually take care of scab. Control chewing insects in the soil.
Stemphylium leaf spot
(Stemphylium spp.)
Small round or angular yellow spots with a red dot in
the center appear on green parts of plants. Spots are
larger on some cultivars. Cultivars differ in susceptibility.
Carried over on gladiolus foliage and refuse. Favored by
warm, wet weather, especially sprinkler irrigation and rain.
Spray mancozeb at 10- to 14-day intervals. Plow under gladiolus crop residues.
Stromatinia rot
(Stromatinia gladioli)
Leaves yellow and die. Leaf sheaths rot at soil level
(neck rot). Rotted tissues appear shredded. Numerous,
very small black fungus resting structures (sclerotia) are
imbedded in dead tissue. Corm lesions are dark brown
and sunken with raised margins.
On diseased corms and in soil for 10 years or more. Favored by wet soil.
Cure and treat corms as outlined at end of this section. Use
uninfested or chemically treated land. Fumigate soil with chloropicrin or a chloropicrin combination.
Disease Control Outlines
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Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Grassy top
(Aster yellows phytoplasma*)
Current season infection results in early maturity, small
corms, and arrested root development. Next year, the
corms produce numerous thin, weak shoots—grassy
top. Flowers produced by grassy top plants are green.
Leafhoppers. Many kinds of plants, including some
weeds.
Destroy infected plants.
Mild mosaic
(Bean yellow mosaic virus)
A faint leaf mottle and sometimes a pencil-stripe color
break of blossoms. Disease is common in nearly all
gladiolus cultivars but symptoms are more severe in
some cultivars. Blossoms may fail to open all the way.
Aphids. Mechanically transmitted by harvesting tools. Legumes (beans, peas, vetch).
Propagate from selected disease-free plants grown in isolated
areas.
Ringspot
(Tobacco ringspot virus,
Yellow or white ring patterns and blotches on leaves.
Nematodes. Mechanically transmitted by harvesting tools.
Many kinds of plants, including weeds.
Destroy infected plants.
White streaking or flecking of leaves and a white blotch
or color break in petals. Flowers sometimes fail to open
completely or shrivel prematurely.
Aphids. Corm-propagated. Sometimes transmitted by harvesting tools. Cucurbits (melons, cucumber, squash), peppers, tomatoes, nandina, and hundreds of other hosts.
Propagate from selected disease-free plants grown in isolated
areas. Rogue infected plants at flowering time or as soon as
virus symptoms appears. Control aphids.
Tomato ringspot virus)
White break
(Cucumber mosaic virus)
Gladiolus are also susceptible to Septoria leafspot (Septoria gladioli) and leaf smut (Urocystis gladiolicola), which are rare diseases in California. Curvularia leafspot (Curvularia lunata) appears occasionally as a neck rot, particularly in cormel stocks.
* For additional information, see section on Key Diseases.
CARING FOR CORMS
The major gladiolus pathogens can be carried on the surface of or inside corms. To control the pathogens, it is essential to correctly cure, store, and dip corms before planting.
Curing: Immediately after digging, place corms in shallow trays in storage rooms maintained at 95°F (35°C) and 80% relative humidity. Use fans to circulate air through and around corms. When old corms break off easily, usually after 6 to 8
days, clean the new corms. Return corms to storage at 95°F and 80% relative humidity for 4 more days.
Storage: Store cured corms at 40°F and 70 to 80% relative humidity. In mild climates, clean corms can be replanted if Fusarium yellows is not a problem.
Preplant dip: Before planting, dip corms in iprodione or thiabendazole plus 4 to 6 fluid ounces of wetting agent/100 gal water. The water should be at a temperature of 80° to 90°F. Allow corms to dry before planting.
Sanitation: Maintain sanitary storage facilities. Burn all gladiolus refuse. Steam treat or disinfect trays, tools, and the like.
Hot water treatment of cormels: (1) Select sound, hard, fully dormant corms grown in warm soil and harvested before cold weather. Cure as outlined. (2) Presoak corms for 2 days in water when the air temperature is 60° to 80°F. Discard
any corms that float. (3) Immerse 30 minutes in water heated to 131°F. (4) Cool immediately with clean, cold water. (5) Dry thoroughly and quickly in warm air or sunshine. (6) Dust with a fungicide and store at 40°F and 70 to 80% relative
humidity.
Disease Control Outlines
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GYPSOPHILA
Gypsophila paniculata (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial gall
(Pantoea agglomerans (formerly
Erwinia herbicola))
Soft, light brown galls up to 2 inches (5 cm) in diameter
develop at or below soil line. Galled plants are often
stunted and some die.
Bacteria survive in galls and in aerial parts of the plant. Infection is favored by warm conditions.
Use pathogen-free stock developed through tissue culture.
Avoid wounding plants when establishing field plantings. Maintain strict sanitation in propagation.
Flower blight
(Alternaria sp.)
Infected flowers turn black.
Favored by moist conditions.
Avoid overhead irrigation during flowering. Protective sprays of
iprodione or chlorothalonil may be helpful in severe situations.
Phytophthora crown rot*
(Phytophthora parasitica)
Leaves wilt and turn light green. Entire plant may collapse and die. Crown tissue is discolored and a soft,
wet decay develops. Secondary bacteria cause the diseased tissue to putrefy.
Pathogen is soilborne and may be present in many fields.
Disease is favored by warm temperatures 90°F, moist
conditions, and poor drainage.
Improve drainage by planting on raised beds. Do not moisture-stress plants, but do not overwater. Soil drenches of oomycete (water mold) specific fungicide are helpful in preventing the disease.
Root rot*
(Pythium spp.)
Soft wet decay of seedlings and plants in propagation.
Leaves of infected plants turn grey-green. In the field,
roots are rotted and plants are stunted.
Several species of Pythium are involved. Pythium aphanidermatum is favored by warm or hot conditions while P.
ultimum develops at lower temperatures. Both pathogens
are present in many field soils. Disease is favored by overwatering and poor drainage.
An oomycete (water mold) specific fungicide is helpful when
used in preventative programs.
Stem rot
(Rhizoctonia solani)
All stages of growth may be affected. Stems are infected at or just beneath the soil line. Sunken dark lesions are dry in the early stages but later the decay becomes soft and wet.
Fungus occurs naturally in many soils. Favored by warm,
wet conditions and deep planting.
Treat soil or planting medium with granular PCNB before
planting. Avoid deep planting. Spray base of plants before or
after planting with iprodione or PCNB. Keep PCNB off foliage.
Gypsophila is also susceptible to gray mold* (Botrytis cinerea), bacterial fasciation (Rhodococcus fascians), root knot nematode** (Meloidogyne spp.), cottony rot* (Sclerotinia sclerotiorum), southern blight* (Sclerotium rolfsii), crown gall* (Agrobacterium tumefaciens), and aster yellows* (Aster yellows phytoplasma).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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HEATHER
Calluna vulgaris, Erica spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Armillaria root rot*
(Armillaria mellea)
Symptoms are similar to crown rot but distribution in the
field is different. Examination of affected plants reveals
white fungus plaques beneath the bark at or below soil
line on main stem. Erica canaliculata and E. hirtiflora
have been infected.
Fungus survives for long periods in infected roots buried in
soil. Infection is favored by the same conditions that are
favorable for plant growth.
Avoid fields just cleared of oaks or other susceptible woody
plants. This is not a common disease of heather.
Chlorosis
(Iron deficiency)
Foliage turns yellow and some turns almost white, especially new growth. Terminal growth may die and
plants are stunted. Occurs if soil pH is too high.
Soils that are too basic as a result of too much calcium.
Spray plants with ferrous sulfate using 6 to 8 pounds/100 gal
water. Thoroughly wet the plants using 100 to 150 gal/acre.
Apply once a month starting in early spring as growth commences. If stems turn black, reduce dosage and frequency of
treatment. Acidify soil.
Powdery mildew*
(Erysiphe azaleae, Golovinomyces orontii)
Shoot tips are reddened, then yellow and turn brown
and fall off. A side bud develops into the new terminal
and successive killing of the tips causes crooked,
twisted growth. The white powdery mildew growth is often difficult to find. Affected plants are stunted and
bushy. Erica persoluta is damaged.
On living heather foliage. Fungus is favored by moderate
temperatures, partial shade, and dry foliage.
Several fungicides are available to protect foliage from infection. Start applications in spring and after each irrigation. During very hot periods, sulfur may damage foliage and flowers;
avoid excessive rates of application.
Root and crown rot
(Pythium spp.*, Phytophthora
cinnamomi*)
Plants are stunted or may suddenly wilt and collapse.
Roots are killed and the base of the stem (crown) is attacked, causing a complete or partial girdling. Erica hirtiflora (=E. regerminans) and E. hyemalis are very susceptible. Erica canaliculata (E. melanthera) is moderately resistant and E. persoluta is resistant.
Soilborne pathogens with wide host range. These organisms also survive in infected plants. Favored by excessive
soil moisture, poor drainage, and warm temperatures.
Avoid introduction into new areas by growing or obtaining disease-free plants. Take cuttings from high on the plant and use
heat-treated or fumigated propagative and growing medium.
Prevent infection in the nursery by periodic treatments with an
oomycete (water mold) specific fungicide. Careful water management will provide some relief in field plantings. Oomycete
(water mold) specific fungicides applied as a drench also
helps.
Rust*
(Uredo ericae)
Small pustules of powdery orange spores occur on
leaves. Infected leaves usually turn yellow and abscise.
Erica hirtiflora and E. persoluta var. alba are infected.
On foliage. Spores are airborne and may be carried by the
wind for many miles. Pathogen is favored by moderately
low temperature and dew or rain.
Protect foliage with sulfur applied as a dust or spray. Start applications in late March and continue at 10- to 14-day intervals
until rains stop. During very hot periods sulfur may cause damage to foliage and flowers; avoid excessive rates of application. Also avoid overhead watering.
Verticillium wilt*
(Verticillium dahliae)
Wilting, yellowing, and defoliation occur frequently on
only one side of the plant. Examination of crown and
roots, which appear healthy, helps differentiate this disease from root and crown rot. Symptoms usually first
appear in early summer. Erica australis and E. persoluta are affected.
Fungus is soilborne and has a wide host range. Fungus invades plant in the cool spring plugging the water-conducting tissues. Symptoms occur when plant is stressed for
water, particularly during warm periods.
Avoid fields that have been in susceptible crops or weeds such
as tomato, chrysanthemum, strawflowers, nightshade, and
others. Propagate plants, using heat or chemically-treated medium. The fungus can be eliminated from field soil by fumigation with chloropicrin or a chloropicrin combination.
* For additional information, see section on Key Diseases.
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IRIS (Bulbous) (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial blight*
(Xanthomonas campestris pv.
tardicrescens)
Elongated, water-soaked spots or lesions that usually
occur near the base of leaves. Under moist conditions,
lesions rapidly enlarge causing leaf to turn yellow and
collapse. Flower stems may be infected.
Bacteria survive in infected bulb scales and tissues. Rhizomatous iris also is susceptible. Disease is favored by
warm, moist conditions and by injuries and frost damage.
Avoid excessive overhead irrigation. Space plants wide
enough to promote air circulation and rapid drying of foliage.
Discard infected plants. Use pathogen-free planting stock.
More info*
Basal rot
(Fusarium oxysporum f. sp.
gladioli)
Stunted, yellowed plants. Basal plate and scales are affected by a firm brown rot. Blue mold may develop as a
secondary rot.
Fungus survives as chlamydospores in soil for several
years. Spread by infected bulbs. Disease is favored by
warm soils (above 57°F). Gladiolus, crocus, Ixia, Tigridia,
Tritoma, and freesias are also attacked.
Do not plant in infested soil for 3 to 4 years or fumigate soil
with chloropicrin or a chloropicrin combination. Dip bulbs in thiabendazole. Fusarium oxysporum f. sp. gladioli has shown
some resistance to thiabendazole and to benzimidazole fungicides.
Black slime
(Sclerotinia bulborum)
Plants yellow, wilt, and die or fail to emerge. Diseased
plants tend to occur in clumps. Below ground shoots
and bulbs are covered with a mass of gray fungus. Infected parts contain pockets of gray or white mycelium
and black sclerotia.
Favored by cool weather. Fungus survives as sclerotia in
soil for several years.
Rotate out of iris for 3 to 4 years. Include PCNB in bulb dip.
Blue mold
(Penicillium spp.)
Plants are stunted, off-color, lack flowers, and prematurely die. Blue-green mold on rotted bulbs. Also common on stored bulbs.
Wounds caused by insects, harvesting, sunburn, etc. are
necessary for infection. Late or early digging favors disease. Frequently starts on corms stored incorrectly.
Avoid very early or very late digging. Avoid injuries. Cure bulbs
rapidly and provide good ventilation during storage. Heat cure
bulbs within 5 days of digging. Dip bulbs in thiabendazole.
Some Penicillium spp. have shown resistance to thiabendazole and other benzimidazole fungicides.
Fire (Leaf spot)
(Mycosphaerella macrospora
=Didymellina macrospora, conidial state Heterosporium gracile)
Oval to elliptical leaf spots with pale yellow or reddish
brown borders. As the spots become old, centers turn
tan. Spots are often near tips of leaves. Flower buds,
stems, and bulbs may be infected. Dark green spores
may be seen in the spots.
Disease is favored by mild temperatures (50° to 70°F)
and wet conditions. Spores are airborne. Fungus also infects rhizomatous iris.
Dig bulbs annually. Protect foliage with myclobutanil, chlorothalonil, or mancozeb. Destroy old leaf tissues.
Ink spot
(Drechslera iridis)
Dark reddish brown elongated spots with chlorotic margins. Older leaves develop gray centers. Dark spore
masses may be visible on lesions. Usually older leaves
are infected. Irregular inky-black stains occur on Iris reticulata bulbs. Disease may be severe on plants left in
the ground for 2 years.
Disease is favored by mild (68° to 77°F), moist conditions.
Fungus survives on infected bulbs and debris. Not common.
Dig bulbs every year. Remove and destroy all debris; rotate on
a 3-year basis. Protect foliage with mancozeb.
Nematode**
(Ditylenchus destructor)
Plants are stunted. Black streaks occur along veins of
the outer husks. Outer husks become shredded at the
base and the basal plate becomes honeycombed and
grayish.
Nematodes survive in bulbs. Damage is worse in cool,
moist climates. Other hosts include alfalfa, potato, sugarbeet, tulips, and some weeds and fungi.
Harvest bulbs 7 to 10 days earlier than normal. Treat dormant
bulbs in hot water (110°F) for 3 hours. Cool and dry promptly.
Disinfect tools, trays, etc. by heat treatment such as steam or
hot water at 185°F. Do not replant infested fields for 2 years.
Continued on next page . . .
Disease Control Outlines
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Iris (Bulbous), continued
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Rust*
(Puccinia iridis)
Reddish brown powdery pustules on leaves. Cultivars
differ in susceptibility.
Fungus survives on living iris leaves. Spores are airborne.
Favored by condensed moisture and overhead irrigation.
Irrigate so that water does not remain on leaves longer than a
few hours. Chlorothalonil, myclobutanil, and mancozeb used to
control leaf spot will help control rust. Remove and destroy old
infected leaves.
Southern blight*
(Sclerotium rolfsii)
This disease is also called crown rot or southern wilt.
Outer leaves turn yellow. Eventually all leaves are affected. Leaf bases and bulb are affected by a soft rot.
White mycelium is present on bulbs and in soil. Small,
tan to reddish brown sclerotia are found in and on bulbs
and soil.
Sclerotia survive in soil. Disease is favored by warm (77°
to 95°F), moist soil. May be spread by infected bulbs and
anything that moves infested soil.
PCNB mixed with soil before planting helps.
Bulbous irises are also susceptible to gray mold* (Botrytis cinerea), gray bulb rot (Rhizoctonia tuliparum), root rot* (Pythium irregulare), neck rot (Rhizoctonia solani), Iris mosaic virus, mosaics, and black storage molds (Rhizopus sp., Aspergillus sp.).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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IRIS (Rhizomatous) (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial soft rot*
(Pseudomonas spp.)
Wilting and dying of fans accompanied by a soft, wet,
foul-smelling rot of rhizome. Fans separate easily from
rotted rhizome or topple over.
In infected tissue. Favored by warm, wet weather, but rot
may continue when conditions are dry. More serious when
rhizomes are buried when planted.
Bacteria enter through wounds, so prevent injuries to plant.
Remove infected plants, cut away rotted tissues, and allow cut
surfaces to thoroughly dry before replanting. Plant high or on
ridges so that the top of the rhizome is not covered.
Leaf spot*
(Mycosphaerella macrospora,
Didymellina macrospora, conidial state; Heterosporium gracile)
Circular to elongated spots 0.125 to 0.25 inch in diameter and up to 1 inch in length. At first, yellowish flecks
appear. Spots later turn light brown and have a distinct
red border. If severely infected, leaves of some cultivars
die back. Dark green spores may be found in spots.
On living and dead leaves. Favored by wet weather. Fungus also infects bulbous iris and other iris species.
Collect and burn or bury dead leaves. Where practical, cut off
infected parts of leaves. Protect foliage during wet weather
with chlorothalonil, myclobutanil, mancozeb, or copper fungicides. Addition of a wetting agent may be necessary.
Rust*
(Puccinia iridis)
Reddish brown, powdery pustules on leaves. Infected
areas frequently surrounded by yellow tissues. Cultivars
differ greatly in susceptibility to rust.
On living iris leaves. Spores are airborne. Favored by atmospheric moisture (rain, dew, overhead irrigation).
Irrigate so that the water does not remain on leaves longer
than a few hours. Chlorothalonil, myclobutanil, and mancozeb
used to control leaf spot will also help control rust.
Southern blight
(Sclerotium rolfsii)
Rhizomes and leaf bases become rotted. The fungus is
visible as a white, cottony growth on the surface and in
the soil, and as small, brown resting structures (sclerotia).
In soil as sclerotia. Favored by high temperatures and wet
soil.
Attacks many other plants. Avoid planting in infested soils. Fumigate soil before planting. To prevent spread, drench infested
areas with PCNB or mix granular form with planting medium
before planting.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Mosaic
(Iris virus 1)
Light and dark green mottling and yellow stippling of foliage. Mottling and stippling are especially prominent on
young leaves. Mosaic is most severe on bulbous iris
and some rhizomatous species. Iris germanica and its
hybrids are only slightly stunted and sometimes exhibit
no symptoms.
Iris family (Iridaceae). Transmitted by aphids. Oncocyclus
iris and their hybrids can be severely damaged. Serious
on Tigridia.
Rogue infected plants. Control aphids.
Rhizomatous irises are also susceptible to root knot nematode** (Meloidogyne hapla). Rhizome rot caused by Sclerotinia convoluta and bacterial leaf blight caused by Xanthomonas tardicrescens, do not occur or are rare in California.
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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MARGUERITE DAISY
Chrysanthemum (=Argyranthemum) frutescens (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Cottony rot*
(Sclerotinia sclerotiorum)
Plants wilt and die. Basal stem rot. Cottony, white mycelium present in and on stems under moist conditions.
Long, black sclerotia form in and on stems.
Fungus survives in soil as sclerotia, which germinate after
a cold-dormancy period to produce airborne spores. Direct
infection from sclerotia may occur. Fungus has a wide
host range. Favored by overhead irrigation and high humidity.
Avoid planting in infested fields or fumigate soil. Treat soil with
PCNB before planting. Carrots, celery, and lettuce are common
hosts. Irrigate early in the day so plants dry quickly. Spray base
of plants and lower foliage with thiophanate-methyl.
Crown gall*
(Agrobacterium tumefaciens)
Spherical galls on stems most often at base of plant.
Heavily infected plants are stunted.
Soilborne bacterium with a wide host range. Survives in
soil for several years.
Plant disease-free plants. Propagate from clean plants. Dip or
spray cuttings with Agrobacterium radiobacter 'K84' immediately
if wounded. Avoid wounds, especially when plants are wet.
Downy mildew*
(Peronospora radii)
Young tip leaves are dull green, severely stunted, and
roll downward. Gray-purple fungus grows on undersides of leaves. Disease is common on seedling phase;
large plants are less frequently attacked. Infected plants
fail to produce flowers.
Thick-walled resting spores (oospores) in dead plant parts.
Airborne spores. Favored by cool (40° to 60°F), wet
weather.
In greenhouse, reduce humidity. Drench seedlings with
an oomycete (water mold) specific fungicide. Do not replant in
fields where disease has been severe. Steam treat to kill resting
spores. Protect foliage with mancozeb.
Pythium root rot*
(Pythium spp.)
Plants stunted as a result of reduced root system. Small
roots rotted.
Soilborne pathogen. Spores spread with soil and water.
Favored by excess soil moisture and poor drainage.
Avoid poorly drained soils. Plant on raised beds. Reduce
amount of irrigation water. An oomycete (water mold) specific
fungicide applied at transplanting will help get plants started.
Root knot nematode**
(Meloidogyne hapla)
Plants are stunted; swellings or galls on roots. Galls
have lateral roots.
Nematodes survive in soil as eggs. Disease is usually
most severe in sandy soils. Also prevalent in cooler climates: optimum temperature to invade roots is 59° to
68°F (15° to 20°C) and for growth and reproductions is
68° to 77°F (20° to 25°C).
Preplant fumigate with chloropicrin or a chloropicrin combination
or solarize soil.
Root lesion nematode
(Pratylenchus spp.)
Plants are stunted. Necrotic lesions on roots that involve the cortex and deeper tissues.
Nematodes survive in soil as adults, larvae, and eggs.
Preplant fumigate with chloropicrin or a chloropicrin combination
or solarize soil.
Southern blight*
(Sclerotium rolfsii)
Plants wilt and collapse. Basal stem and roots are rotted. White cottony fungus growth may be present on infected parts and soil. Small (0.625 inch), tan or brown
sclerotia form on rotted tissues and in soil.
Sclerotia survive in soil. No airborne spores are formed.
Sclerotia germinate and infect susceptible plants. Fungus
has a wide host range.
Avoid fields where the disease has occurred or fumigate with
chloropicrin or a chloropicrin combination. PCNB applied to the
base of plants or as a preplant treatment will help.
Marguerite Daisy is also susceptible to powdery mildew* (Golovinomyces cichoracearum), Verticillium wilt* (Verticillium dahliae), leaf spot (Ramularia sp.), curly top (Beet curly top virus), and aster yellows (Aster yellows phytoplasma).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
NARCISSUS
Narcissus spp. (11/20)
Disease (causal agent)
Basal rot
(Fusarium oxysporum f. sp. narcissii)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Infected plants are stunted with distorted and yellow
leaves, and usually die. The basal plate is decayed and
reddish brown in color. The white to pinkish fungus is
sometimes seen at the base between the scales. Eventually the bulb rots.
Fungus survives as chlamydospores in soil for long periods. Short rotations are not effective. Disease is favored
by warm soils and is limited below 55°F; disease is favored by high levels of nitrogen fertilization. Potassium fertilizer may decrease disease sensitivity.
Avoid excessive fertilization. Dig up bulbs in diseased areas as
soon as possible. Store bulbs below 64°F. Dip bulbs in thiabendazole as soon as possible after digging. Hot water treatment (see stem and bulb nematode) is also effective in reducing
the disease. Rotate out of narcissus for at least 3 years. Plant
when soil is cool.
Susceptibility of narcissus cultivars to basal rot:
Susceptible: Carlton, Golden Harvest
Moderately susceptible: Toorak Gold, Dutch Master, Hollywood
Moderately resistant: Malvern City, Rijinveld's Early Sensation, White Lion, Soleil d'Or, Dulcimer
Resistant: St. Keverne
Crown rot or Southern blight
(Sclerotium rolfsii)
A bulb rot that is at first wet and later becomes dry and
woody. A white fungus mat and small (0.03–0.125
inch), round, tan to brown sclerotia occur on decaying
bulbs and in surrounding soil.
Disease is favored by warm weather. Fungus survives in
soil for long periods (10 years). Fungus has a wide host
range. Can be spread by infected bulbs.
Avoid infested fields for 4 years or longer. Deep plowing is
sometimes practiced to bury sclerotia. Treat bulbs in hot water.
(See stem and bulb nematode.) PCNB applied in the furrow at
planting can be effective.
Fire
(Botryotinia polyblastis)
Water-soaked areas on petals that become brown and
wither. Flowers are attacked first, and later the foliage.
Foliage spots are small, elliptical, tan and usually near
the tips. Yellow streaking follows the leaf spots.
Fungus survives as sclerotia in leaf debris. Sclerotia germinate in spring to produce fruiting bodies (apothecia),
which produce airborne spores (ascospores). Conidia,
which are also airborne, cause secondary spread. The disease is favored by mild, humid conditions.
Remove flowers before fungus produces apothecia in
March/April. Protect flowers and foliage with a fungicide.
Scorch
(Stagonospora curtsii)
Yellow to brown lesions at leaf tips. Elongate reddish
brown leaf spots. Small black pycnidia form in necrotic
areas.
The fungus survives in the neck and between scales. Disease is favored by mild, moist conditions. Spores are
spread in splashing water. The fungus infects members of
the Amaryllidaceae.
Treat bulbs with hot water. Protect plants in the field with fungicides. Make first application as leaves emerge.
Smoulder
(Botrytis narcissicola)
A dark brown lesion first appears on leaf tips. Infected
leaves may curl when infection occurs on inner edge.
Masses of fuzzy gray spores (conidia) and small black
sclerotia form on diseased tissues, especially near soil.
Fungus survives in infected bulbs and as sclerotia in soil.
Conidia are airborne. Favored by cool, wet weather.
Rotate with other crops. Dig bulbs early. Dip bulbs in suitable
fungicide such as thiabendazole. If disease is severe in field,
spray with iprodione, fenhexamid, or thiophanate-methyl.
Continued on next page . . .
Disease Control Outlines
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Narcissus, continued
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Stem and bulb nematode**
(Ditylenchus dipsaci)
Leaves are stunted and distorted, and often swollen
and thickened near the base. Yellow or brown swellings
occur in leaf centers and margins. Severely infected
bulbs are unproductive and may rot.
Nematodes survive in infected bulbs and in bulb debris in
fields for about 3 years. Optimum temperature for infection
and reproduction is 50° to 60°F. (Little activity occurs
when soil temperatures are lower than 50°F and greater
than 68°F.) Nematodes are spread by irrigation water and
equipment. They also survive in weed hosts and can survive desiccation.
Remove infected plants and surrounding plants from the field.
Clean equipment after use in diseased fields. Treat bulbs in hot
water. Store bulbs at 60° to 64°F before treatment to reduce
heat injury. Presoak bulbs 2 to 3 hours or overnight in water
plus a wetting agent at 75°F. Increase temperature in morning
to 109°F. Once the temperature of the treatment solution
reaches 109°F, maintain a constant temperature of 109° to
111°F for 3 to 4 hours. Cool and dry bulbs immediately.
CAUTION: Hot water treatment may injure bulbs causing stunting and flower blast or deformation. Obtain expert advice before
large-scale treatment.
White mold
(Ramularia vallisumbrosae)
Small, sunken, grey or yellow spots on leaves and
green parts. Spots enlarge and darken to a yellow- brown with yellow margins. Masses of white, powdery spores (conidia) occur on leaves under moist conditions. Small, dark sclerotia are produced in older infected tissues.
Fungus survives as sclerotia in dead leaves and on bulbs.
Sclerotia germinate to produce conidia as leaves emerge.
Disease is favored by warm, moist conditions.
Do not replant for 1 year in fields where the disease has occurred. Protect foliage with mancozeb. Copper fungicides are
also helpful.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
White streak
(Narcissus white streak virus)
Narrow, dark green to purple streaks, which later become white to yellow-white, appear in leaves and flower
stalk after flowering. Bulb size and yields are reduced
by premature senescence.
Narcissus is the only host of the virus, which is transmitted
by aphids. Symptoms do not occur until air temperatures
exceed 64°F.
Eliminate infected plants. Control aphids.
Yellow stripe
(Narcissus yellow stripe virus)
Conspicuous light green to yellow streaks and mottling
of leaves and flower stalk, which occurs shortly after
emergence. Sometimes leaves are distorted and a
color-break of flowers occurs. Bulb yields are reduced.
The virus infects only narcissus and is spread by aphids.
Symptoms appear early in growing season.
Eliminate infected plants. Control aphids.
Equipment that has come into contact with diseased bulbs should be thoroughly cleaned by heat treatment.
Narcissus may become infected by a number of other viruses; some produce inconspicuous symptoms. Narcissus is also susceptible to Stromatinia dry rot (Stromatinia narcissi), black slime (Sclerotinia bulborum), soft rot (Rhizopus stolonifer),
bacterial streak (Pseudomonas sp.) and root lesion nematode** (Pratylenchus penetrans).
** For additional information, see section on Nematodes.
Disease Control Outlines
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PEONY
Paeonia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Gray mold*
(Botrytis cinerea or
B. paeoniae)
Leafy shoots wilt and fall over as a result of rotting at
the base. Fuzzy gray fungus sporulation is usually visible on infected tissues. Flower buds darken and wither;
leaves also may be attacked.
Disease is favored by wet weather and injured tissue.
Fungus survives on plant debris and as sclerotia in or on
soil.
Remove or burn old growth in fall. Cut stalks below the ground
level. Planting on raised beds also is helpful. Treat with fenhexamid.
Leaf blotch
(Cladosporium paeoniae)
Small (0.02 to 0.04 inch), oval leaf spots that reach a
diameter of 0.08 to 0.12 inch before they penetrate
through the thickness of leaf. As spots enlarge, they
merge giving the leaf an irregular, blotchy appearance.
The upper surface of spots become purple while the
lower surface is a dull brown.
Fungus survives on infected peony debris and probably on
infected scales of crown buds. Disease is favored by rainy
weather in spring.
Burn or remove plant residues in fall. Protect foliage in spring
with a fungicide starting as soon as green shoots appear.
Phytophthora blight
(Phytophthora cactorum)
Young shoots turn black and die or cankers appear
along stems and cause them to collapse. Crown infections produce a wet rot that often destroys the entire
plant.
Favored by cool, wet conditions such as very heavy rains,
excessive irrigation, and poor drainage.
Grow plants in raised beds. Do not overwater. Some of the fungicides effective against Phytophthora spp., such as
mefenoxam, would probably be helpful.
Verticillium wilt*
(Verticillium dahliae)
Plants wilt at flowering, but no basal rots are present.
The water-conducting tissue (xylem) in stems is discolored. Infected plants may appear to recover, but symptoms will reoccur the following year. Fungus is systemic
in plant.
Disease is favored by cool, rainy weather and hot weather
at flowering. Water stress exacerbates the disease. Fungus has a wide host range and survives for many years as
microsclerotia in soil.
Avoid fields where susceptible plants such as tomatoes, cotton,
strawberries, chrysanthemum, and others have been grown. Fumigate soil with chloropicrin or a chloropicrin combination. Do
not propagate from plants that exhibit any symptoms of the disease.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Le Moine Disease
(cause unknown)
Plants are dwarfed with many spindly shoots that fail to
form flowers. Roots of affected plants are often irregularly swollen. The disease slowly spreads in plantings in
a manner suggesting a soilborne vector.
Plants are systemically affected and do not recover.
Destroy infected plants.
Ringspot
(Peony ringspot virus)
A marked yellow mottle that is in the form of chlorotic
rings occasionally accompanied by small necrotic
spots. Growth is probably reduced but not obviously.
Virus is systemic in infected plants. The virus is mechanically transmitted but little else is known about natural
transmission.
Destroy infected plants.
Peonies are also susceptible to Armillaria root rot* (Armillaria mellea), crown gall* (Agrobacterium tumefaciens), and black root rot* (Thielaviopsis basicola).
* For additional information, see section on Key Diseases.
Disease Control Outlines
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POINSETTIA
Poinsettia spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial canker*
(Curtobacterium flaccumfaciens
pv. poinsettiae)
Longitudinal water-soaked lesions on stems and petioles.
Spotting of leaves and defoliation. In advanced stages,
stem lesions split open.
Infected poinsettia plants and debris. Favored by
warm, moist conditions. Bacteria spread in water.
Bacteria may be present in symptomless plants and
cuttings.
Plant pathogen-free cuttings. Avoid overhead irrigation and syringing. Steam soil and disinfect benches with copper naphthenate; disinfect tools.
Bacterial leaf spot* (Xanthomonas
campestris subsp. poinsettiaecola)
Spots start out on the undersides of leaves, expand, and
become visible on the upper surfaces. Spots are grey to
brown, becoming darker as they expand. Generally, they
are surrounded by a water soaked area of lighter green or
yellow.
Infected poinsettia plants and cuttings can survive in
dried leaf debris for one year. Favored by high humidity, warm temperatures, and close plant spacing.
Prevention is the best management strategy, primarily by avoiding overhead watering that allows splashing of bacteria to adjacent plants. Once present, discard affected plants and disinfect
benches. Control can be difficult, but sprays of copper compounds have shown some level of success.
Bacterial stem rot
(Dickeya (=Erwinia) chrysanthemi)
Watery, soft rot of cuttings or stems, resulting in disintegration of infected tissues. Rot develops rapidly and plant collapses.
In diseased plant tissues. Favored by high temperatures (73° to 86°F) and succulent plants.
Avoid high temperatures and practices that produce succulent
growth. Careful sanitation practices will minimize spread of bacteria. Disinfect tools with quaternary ammonium.
Gray mold*
(Botrytis cinerea)
Blasting of flowers and browning or spotting of bracts.
Fuzzy gray fungal growth forms on dead parts. Lesions on
stems and leaves.
In plant debris. Favored by cold, moist conditions
and condensed moisture on bracts and flowers.
Provide better growing conditions and air circulation. Clean up
plant debris. Avoid wetting leaves and try to lower relative humidity. Protect plants with fenhexamid.
Greasy canker
(Pseudomonas viridiflava)
Greasy-appearing cankers on stems. Necrotic lesions with
chlorotic margins on leaves. Sometimes confused with bacterial canker.
Infected plant debris. Bacterium has a wide host
range. Disease favored by high humidity, high temperature, and condensed moisture on plants.
Reduce humidity. Sanitize pruning tools. Avoid wetting foliage.
Powdery mildew* (Oidium spp.)
Yellow spots or whitish growth on upper leaf surfaces and
bracts.
On living plants. Favored by moderate temperatures
and crowded, shaded foliage.
Regularly inspect plants. Remove, bag, and dispose of infected
plants at first sign of infection. Apply protectant fungicide when
plants are young and more easily sprayed.
Root and stem rot*
(Thielaviopsis basicola, Rhizoctonia solani, Pythium spp.)
Plants are stunted and wilt easily. Lower leaves become
chlorotic and may fall. Roots are rotted and dark brown, water-soaked stem lesions develop. Large roots and lower
stem may be enlarged and ridged. Young plants frequently
are killed. Each fungus can cause disease independently,
or fungi may interact to produce rapid decline. Symptoms
vary with the pathogen.
In soil. Favored by excess moisture and overcrowding of plants. Thielaviopsis and Pythium severe at
high (86°F) or low (63°F) soil temperatures, whereas
Rhizoctonia develops most rapidly between 63° to
79°F. Disease development most severe at rooting
and just before maturing.
Plant disease-free cuttings in heat-treated or chemically
treated soil. Before planting, mix into soil mefenoxam plus thiophanate-methyl. If root rots occur after potting, drench with
mefenoxam plus thiophanate-methyl.
Rust*
(Uromyces euphorbiae)
Pustules of cinnamon-brown spores on both leaf surfaces.
On living plants. Favored by moist conditions.
Pick off and burn diseased leaves. Protective fungicide sprays
help in control.
Spot anthracnose or scab
(Sphaceloma poinsettiae)
Circular, buff-colored spots that develop into scablike lesions on leaves and stems.
Infected plants and debris. Favored by wet conditions. Spores spread in water.
Do not wet foliage. Protective fungicidal sprays should help in
control. Avoid splashing water.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Mosaic
Distortion of leaves and bracts. Some bracts may fail to
May be symptomless in poinsettias. Mechanically
Obtain virus-free plants. Grow at higher temperatures. Discard
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(Poinsettia mosaic virus)
color normally. Mild mottling of leaves. Angular leaf spotting, apparent only under cool temperatures. Symptoms
most severe on plants grown at 61° to 68°F. Plants grown
at 75° to 82°F appear normal.
transmitted.
plants with symptoms.
Poinsettias are also susceptible to Rhizopus soft rot (Rhizopus stolonifer).
* For additional information, see section on Key Diseases.
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POT MARIGOLD
Calendula officinalis (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Powdery mildew*
(Podosphaera xanthii)
White, powdery mildew fungus on surface of leaves and
stems. More common on older leaves and older plants.
Disease is favored by moderate temperatures and somewhat shaded conditions; however, powdery mildew may
occur on lower leaves of plants in full sun. Spores (conidia) are windborne.
Protect plants with a powdery mildew fungicide.
Root rot*
(Phytophthora spp.)
Plants are stunted and somewhat chlorotic. Roots are
rotted.
Phytophthora spp. are present in many field soils. Favored
by poor drainage, heavy soils, or overwatering.
Plant on raised beds. Drench soil with an oomycete (water
mold) specific fungicide.
Smut
(Entyloma calendulae)
Circular to irregular (0.25 to 0.5 inch in diameter),
greenish yellow to brownish spots, sometimes with a
darker brown border. Spots are somewhat thickened
and evident on both sides of the leaf.
Spores are windborne or rainborne. Fungus survives on
Calendula and Calendula refuse, and probably on other
related hosts. Favored by rain and overhead irrigation.
Avoid overhead irrigation. Protect foliage with mancozeb.
Pot marigolds are also susceptible to Pythium root rot* (Pythium spp.), gray mold* (Botrytis cinerea), rust* (Puccinia melampodii), spotted wilt (Tomato spotted wilt virus), root knot nematode** (Meloidogyne spp.), aster yellows* (Aster yellows phytoplasma), mosaic (Cucumber mosaic virus), southern blight* (Sclerotium rolfsii), cottony rot* (Sclerotinia sclerotiorum), Alternaria leaf spot (Alternaria sp.), Charcoal root rot (Macrophomina phaseolina), stem rot* (Sclerotinia sclerotiorum), and Verticillium
wilt* (Verticillium dahliae).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
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ROSE
Rosa spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Armillaria root rot*
(Armillaria mellea)
A general decline and eventual death. White plaques of
fungal growth develop between bark and wood.
In infected wood buried in soil. Could be introduced with
leaf mold if there are woody branches or roots present or
in incipient infection on plant.
Fumigate infested soil with chloropicrin or a chloropicrin combination.
Black spot*
(Diplocarpon rosae)
Black spots with fringed margins mainly on both sides
of leaves and on succulent stems. Yellowed areas develop around spots. Causes defoliation.
On living and dead leaves, and on infected stems. Waterborne spores are spread by splashing water.
Avoid wetting foliage. Remove, incorporate, or burn infected
fallen leaves when pruning. Protect foliage with chlorothalonil.
Do not compost unless using rapid methods.
Botrytis blight*
(Botrytis cinerea)
Spotting of flower petals and bud rot. Twig dieback and
cane canker. Fuzzy gray fungal spores form on decayed tissues.
Plant debris. Favored by high humidity, condensed moisture, and low temperatures. Spores are airborne.
Clean up debris. Protect susceptible tissues with chlorothalonil,
iprodione, mancozeb.
Canker diseases
(Coniothyrium fuckellii, Botryosphaeria dothidea, Cryptosporella umbrina)
Brown cankers, sometimes with gray centers. Small,
black, spore-producing fungal structures (pycnidia) develop in dead tissues.
On dead plants and debris. Favored by wet weather.
Spores are waterborne. Infection occurs mainly through
wounds.
Keep plants in vigorous condition. Prune diseased portions.
When pruning, cut back to node.
Crown gall*
(Agrobacterium tumefaciens)
Overgrowths or galls form on stem and roots. Infection
occurs mainly through wounds.
In soil. Bacteria spread in water. Gall development is favored by rapidly growing host.
Avoid injuring base of plant and roots. Paint galls with Gallex to
eradicate them. Use good sanitation in propagating areas.
Downy mildew*
(Peronospora sparsa)
Purplish red to dark brown, irregular angular spots on
leaves. Lower surface covered with sparse, downy fungal growth that may be hard to see. Leaves turn yellow
and fall.
Spores produced only on living plants. Resistant spores
(oospores) carry fungus over unfavorable periods. Moist,
humid conditions.
Protect foliage with mancozeb, fosetyl-al, or mefenoxam.
Powdery mildew*
(Podosphaera pannosa var.
rosae)
White-to-gray powdery growth on leaves and other
green parts, mainly on new growth. Leaves are distorted and discolored.
On living plants and in infected buds. Favored by moderate temperatures (60° to 80°F) and high relative humidity
at night (90 to 99%).
Protect foliage with myclobutanil, neem oil, propiconazole, stylet
oil, potassium bicarbonate, or sulfur. Eradicate infections with
horticultural oils, neem oil, or jojoba oil.
Rust*
(Phragmidium disciflorum or
P. speciosum, P. tuberculatum)
Small orange pustules on undersides of leaves and
other green parts. Leaves frequently are yellow. May
cause defoliation. Cultivars differ widely in susceptibility. In fall, black teliospores form on leaves.
On living leaves; rarely on stems. Favored by cool, moist
weather, and condensed water on leaves. Spores are airborne.
Avoid overhead irrigation. Protect foliage with myclobutanil, triadimefon, or mancozeb. Remove and destroy all leaves during
winter months.
Verticillium wilt*
(Verticillium dahliae)
Leaf fall is followed by dieback of one or more shoots.
One-sided purpling of stems sometimes present.
In soil for many years. May go undetected in budwood.
Symptoms are most severe during warm weather following
a cool period.
Fumigate infested soil. Obtain disease-free plants. Manetti rootstock is resistant to most strains of the fungus.
Continued on next page . . .
Disease Control Outlines
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Rose, continued
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Mosaic
(Prunus necrotic ringspot virus,
Rose mosaic virus (=Apple mosaic virus), Arabis mosaic virus
among others. Mixed infections
common.)
Symptoms vary with rose cultivar and virus. Symptoms
range from general yellowing to conspicuous yellow
blotches and intricate rings with line patterns. Plants
may be somewhat stunted.
Carried in living plants and spread by budding and grafting
and by rooting cuttings from infected plants. No insect vectors known. Arabis mosaic virus can be transmitted by
nematodes. Symptoms appear at moderate-to-low temperatures and are masked at high temperatures.
Obtain virus-free plants. Heat treatment helps control the virus
in rose stocks; 100°F temperatures for 4 weeks inactivates virus
in 99% of cuttings taken from treated plants.
Rose leaf curl
(probably a virus)
Downward curling of leaves and cane dieback. Leaves
readily fall from new shoots, which are characteristically
pointed with a broad base.
Infected rose plants. Slow natural spread.
Obtain healthy, symptomless plants. Destroy infected plants.
Rose ring pattern
(probably a virus)
Symptomless or inconspicuous in some cultivars, especially floribunda types. Rosa multiflora 'Burr' is severely
stunted with small, deformed leaflets that have a distinct mottling and wrinkling. Most hybrid teas show
green mosaic and fine-line patterns in few or many
leaves.
Infected rose plants. No natural spread. Readily transmitted by grafting.
Obtain virus-free plants. Virus is sensitive to thermal inactivation. (See Mosaic)
Rose spring dwarf
(probably a virus, RSDaV)
Leaves that emerge in spring are balled or recurved on
very short shoots and exhibit conspicuous vein clearing.
Symptoms tend to disappear later in growing season.
Infected rose plants. No natural spread.
Obtain virus-free plants.
Roses are also susceptible to crown canker (Cylindrocladium scoparium), gray mold* (Botrytis cinerea), hairy root (Agrobacterium rhizogenes), root lesion nematode** (Pratylenchus spp.), root knot nematode** (Meloidogyne spp.), and virus diseases:
leaf curl (virus suspected), Rosette (virus suspected), and streak (virus suspected).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
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SHASTA DAISY
Chrysanthemum maximum (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Plant disease-free plants. Fumigate soil with chloropicrin or a
chloropicrin combination.
Acremonium wilt
(Acremonium strictum)
Wilting, stunting, chlorosis and necrosis, often unilateral, of lower leaves. Vascular browning. Symptoms often develop with the onset of flowering.
Soilborne fungus. Disease is intensified if plants are
stressed by excessive soil moisture. Fungus has a wide
host range, including many weeds.
Cottony rot*
(Sclerotinia sclerotiorum)
Plants wilt and die. Basal stem rot. Cottony, white mycelium present in and on stems under moist conditions.
Large black sclerotia form in and on stems.
Fungus survives in soil as sclerotia that germinate after a
Avoid planting in infested fields or fumigate soil. Carrots, celery,
cold-dormancy period and produce airborne spores, which and lettuce are common hosts. Treat soil with PCNB before
infect only dead or dying tissue. Direct infection from sclero- planting. Protect plants with thiophanate-methyl.
tia may occur. Fungus has a wide host range. Optimum
temperature for germination of fungus is 56° to 59°F and
needs high soil moisture for at least 10 days.
Fasciation
(Rhodococcus fascians)
Short, swollen clumps of distorted shoots that do not
elongate at the base of plants. Vigor of plant is reduced.
Secondary rotting of clumps may kill plant.
Bacteria survive on infected plants and debris. Bacterium
has a wide host range. Spreads in water.
Plant disease-free plants. Avoid injuries to base of plant, especially when plant is wet. Control is difficult; plants may have to
be discarded.
Leaf spot*
(Septoria leucanthemi)
Brown, circular and irregular spots on leaves. Heavily
infected leaves yellow and die. Minute black dots (pycnidia) are visible in the center of spots.
Fungus survives on infected plants and debris. Spores are
spread by splashing water. Pathogen needs condensed
moisture to germinate and infect.
Use disease-free plants. Rotate land for 2 years. Avoid overhead irrigation and cultural operations when foliage is wet. Protect plants in rainy weather with chlorothalonil or thiophanatemethyl.
Pythium root rot*
(Pythium spp.)
Plants stunted as a result of reduced root system. Small
roots rotted.
Soilborne pathogen. Spores spread with soil and water.
Favored by excess soil moisture and poor drainage.
Avoid poorly drained soils. Plant on raised beds. Reduce
amount of irrigation water. An oomycete (water mold) specific
fungicide applied at transplanting will help get plants started.
Root knot nematode**
(Meloidogyne hapla)
Plants are stunted. Swellings or galls on roots.
Nematodes survive in soil as eggs. Disease is usually
most severe in sandy soils and in warmer climates.
Preplant fumigate soil with chloropicrin/chloropicrin combination
or a nematicide or solarize soil.
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
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SNAPDRAGON
Antirrhinum majus (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Black root rot*
(Thielaviopsis basicola)
Roots are girdled by decay; tops slowly die. In less severe cases, elongated, black lesions occur on roots.
Disease is particularly damaging to seedlings.
Soilborne fungus; produces dark, resting spores. Spores
are spread in water. Favored by cool, wet soils.
In greenhouse, steam or chemically treat soil. Before planting,
incorporate thiophanate-methyl into top 3 inches of soil.
Cottony rot*
(Sclerotinia sclerotiorum)*
Infections girdle plant stems. Cottony fungal growth or
large, black sclerotia develop inside stems. Dead stems
take on a bleached, white color.
As sclerotia in soil. Airborne spores produced by sclerotia,
which infect dead or weak tissues. Sclerotia produce hyphae, which infect plant tissues. Favored by wet weather.
In greenhouse, steam treat or fumigate soil. Treat soil with
PCNB before planting. Protect plants with iprodione, or thiophanate-methyl. Mancozeb also helps control this fungus.
Damping-off and stem rot*
(Rhizoctonia spp., Pythium spp.,
Phytophthora spp.)
Seedlings killed. Stems rot at soil line. If problem is
caused by Pythium, it usually begins at root tips.
Soilborne organisms. Favored by conditions unfavorable
for plant growth.
Steam treat or fumigate soil. Incorporate PCNB into top inch of
soil before transplanting, or spray bases of plants with thiophanate-methyl or iprodione to control Rhizoctonia. Include an in
preplant treatment or use later as a drench to protect against
Pythium and Phytophthora spp.
Downy mildew*
(Peronospora antirrhini)
Young tip leaves are dull green, severely stunted, and
roll downward. Gray-purple fungus grows on undersides of leaves. Disease is common on seedling phase;
large plants are less frequently attacked. Infected plants
fail to produce flowers.
Thick-walled resting spores (oospores) in dead plant parts.
Airborne spores. Favored by cool (40° to 60°F), wet
weather.
In greenhouse, reduce humidity. Drench seedlings with
mefenoxam or oomycete- or water mold- specific fungicide. Do
not replant in fields where disease has been severe. Steam
treat to kill resting spores. Protect foliage with mancozeb.
Gray mold*
(Botrytis cinerea)
Brown, water-soaked decay of flowers, leaves, and
stems. Fuzzy gray fungal spores form on rotted tissues.
Frequently found on stems of cut flowers.
In plant debris. Airborne spores. Favored by continued
cool, moist conditions.
Reduce humidity in greenhouse. Clean up all plant debris. Protect foliage with iprodione or fenhexamid. Mancozeb also helps
control gray mold.
Powdery mildew*
(Golovinomyces orontii)
White, powdery fungus grows on both leaf surfaces.
Severely infected leaves may be killed.
On living leaves. Airborne spores; not in soil or on seeds.
Favored by moist, shaded conditions, and dry foliage.
Protect foliage with triadimefon or sulfur.
Rust*
(Puccinia antirrhini)
Pustules of dark brown to purple powdery spores develop on leaves and stems. Rapid water loss from severely rusted leaves causes them to dry up.
On living snapdragon plants and spores on seed. Does
not survive in soil, but does in plant refuse. Airborne
spores. Favored by abundant dew, cool nights (50° to
55°F), and warm days (70° to 75°F).
In greenhouse, avoid wetting foliage and prevent moisture condensation at night by balancing heat and ventilation. Protect foliage with myclobutanil or triadimefon. Mancozeb also helps protect foliage from infection. Remove and destroy infected plants.
Verticillium wilt*
(Verticillium dahliae)
Plants wilt, frequently on one side. Wilting is more pronounced near time of bloom. Problem is most important
in seed fields.
In soil for many years. Favored by cool weather. Plants
wilt during hot weather.
Steam treat or fumigate soil with a chloropicrin or a chloropicrin
combination or solarize soil.
Water mold root rots
(Pythium spp. and Phytophthora
spp.*)
Plants are stunted, wilt, or suddenly collapse. Roots decay. Plants fail to "push" after flowers are cut. Remaining stubs are more susceptible to gray mold.
Soilborne pathogen. Favored by heavy, waterlogged soils.
Avoid planting on poorly drained soils. Do not overirrigate.
Steam treat or fumigate greenhouse soil. Drench plants with oomycete (water mold) specific fungicide.
Snapdragons are also susceptible to collar rot (Rhizoctonia solani), crown gall* (Agrobacterium tumefaciens), leaf and stem spot (Phyllosticta antirrhini), mosaic* (Cucumber mosaic virus), root knot nematode** (Meloidogyne spp.), and stem rot
(Phyllosticta antirrhini). Anthracnose (Colletotrichum antirrhini) is important elsewhere but is not found in California.
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
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STATICE
Limonium spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Anthracnose
(Colletotrichum gloeosporioides)
Plants wilt and become mildly chlorotic. Crown tissues
decay and plant may die. In initial stages, roots are not
affected. The fungus also causes leaf, stem, and flower
spots, but this phase of the disease is not common in
California. Gold Coast cultivar is highly susceptible;
blue and white cultivars are more tolerant.
The fungus survives on infected plants and debris. The
disease is favored by wet weather and overhead irrigation. Spores are spread by splashing water.
Avoid overhead irrigation. Protect plants with chlorothalonil
or copper. Chlorothalonil may cause blackening of flowers.
Cercospora leaf spot
(Cercospora insulana)
Small, dull red lesions that enlarge up to 0.67 inch (15
mm) and become tan and membranous in the center
with reddish borders.
Spores are airborne. Disease is favored by warm, moist
conditions and condensed water on foliage.
Avoid overhead irrigation. Protect foliage with chlorothalonil.
Downy mildew*
(Peronospora statices)
Bluish gray sporulation occurs on undersides of leaves.
On upper surface of leaves, infections appear as light
green areas that turn yellow, then coalesce, and eventually the leaf dies. In California it is currently found on
cultivars in the "Misty" series; in Europe it occurs on
many Limonium species.
Unlike powdery mildew fungi, this fungus requires very
wet conditions to flourish. Favored by cool temperature.
High relative humidity (90% or greater) and free moisture
required for spores to germinate and infect plants. Spores
require a minimum of 8 hours of wetness before infection
occurs.
In greenhouse, provide good air circulation and keep relative humidity below 85%. Avoid wetting foliage, using drip
instead of overhead irrigation if possible. Remove infected
plants immediately. Protect foliage with fungicides if necessary.
Gray mold*
(Botrytis cinerea)
Rot of leaves, stems, and flowers. Rot may enter
crowns and kill plants. Fuzzy gray fungus sporulation
develops on decayed tissues. Flower stubs remaining
after flower harvest are particularly susceptible. The
fungus also may kill seedlings.
Fungus has a wide host range and develops on dead
plant parts. Spores are airborne. The disease is prevalent
in California in cool (below 77°F) rainy weather.
Clean up plant debris. Incorporate crop residue into soil as
soon after harvest as feasible. Avoid overhead irrigation especially when flowers are present. Protect plants with iprodione or fenhexamid.
Verticillium wilt*
(Verticillium dahliae)
Plants are stunted. Lower leaves yellow, wilt, and dry.
The fungus, which has a wide host range, survives in soil
as microsclerotia.
Fumigate soil with chloropicrin or a chloropicrin combination. Heat, fumigate, or solarize soil used in production of
transplants.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Aster yellows*
(Phytoplasma)
Stunted growth, multiple production of short stalks,
malformation and bunching of young leaves. Leaves
on more mature plants are reddened in the basal rosette. Flowers are abnormal: reduced size, abnormal
shape and color (frequently green), and may fail to
open.
Phytoplasma is transmitted by leafhoppers.
Control insects. Destroy infected plants.
Turnip mosaic*
(Turnip mosaic virus)
Plants are stunted and have a mosaic pattern of light
and dark green in leaves. Plants infected when young
often die. Leaves may be distorted.
Virus is transmitted by several different aphids and is
common in many weedy plants in the mustard family
(Cruciferae).
Control nearby cruciferous weeds. Control aphids.
Statice is also susceptible to powdery mildew* (Erysiphe polygoni), rust* (Uromyces spp.), bacterial crown rot (Pseudomonas spp.), southern blight* (Sclerotium rolfsii), Broad bean wilt virus, Cucumber mosaic virus, Statice virus Y, Tobacco rattle
virus, Tomato bushy stunt virus, and root knot nematode** (Meloidogyne spp.).
* For additional information, see section on Key Diseases.
** For additional information, see section on Nematodes.
Disease Control Outlines
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
STOCK
Matthiola spp. (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Bacterial blight*
(Xanthomonas campestris pv.
incanae)
Basal leaves turn yellow and drop. Leaf scar is blackened. Soft, water-soaked stem cankers later become
dark and sunken. Plant stems may break and fall over
because they are weakened by the cankers. Black discoloration of the vascular system occurs.
Seedborne and in plant debris; also in soil for 2 years. Favored by cool, wet weather. Bacteria are spread by water.
When buying seed, specify that it be grown from seed treated
in hot water (122° to 131°F for 10 minutes). Follow a 3-year
crop rotation. Avoid splashing water.
Cottony rot*
(Sclerotinia sclerotiorum)
Girdling infections that cause stems to turn chalky
white. Cottony, white masses of fungus or large, black
sclerotia develop on and in stems. Black sclerotia may
develop in seed pods in the shape of stock seed.
As sclerotia in soil. Airborne spores produced by sclerotia
only infect weak or dying tissue. Sclerotia also produce hyphae that infect plant. Favored by cool, moist conditions.
Avoid fields where disease has occurred (common disease of
many vegetable crops). Apply PCNB to soil before planting.
Spray foliage with thiophanate-methyl combined with mancozeb.
Foot rot or wire stem*
(Rhizoctonia solani)
Brown rot of stem occurs at the soil line; area later becomes a dry, sunken canker. Stems are girdled. Brown
fungus strands are visible with a hand lens. Also
causes damping-off of seedlings.
Soilborne fungus. Favored by warm, moderately moist
soil.
Use PCNB on soil before planting. Spray iprodione or thiophanate-methyl over the row and bases of plants.
Fusarium wilt*
(Fusarium oxysporum f. sp.
mathioli)
(important in seed fields)
Lower leaf veins turn yellow, then entire leaf becomes
yellow, withers, and drops. Basal leaves are affected
first. Plants are stunted. Seed pods turn a light-tan
color. Brown vascular discoloration occurs.
Soilborne for many years; also seedborne. A
warm-weather disease; rarely a problem in the winter
grown cut-flower crop.
No control necessary for the cut-flower crop grown in cool,
coastal areas. Fumigate soil with a chloropicrin or a chloropicrin combination (tarped).
Gray mold*
(Botrytis cinerea)
A soft, brown decay that occurs on flowers or entire
flower heads. Fuzzy gray fungus spores form on decayed tissues. Decay may also start on dead leaves
and rot the growing points and flower buds.
In plant debris. Favored by cool, moist conditions and condensed moisture on plants. Spores (conidia) are airborne.
Protect flowers with thiophanate-methyl in combination with
mancozeb or treat with iprodione. Avoid overhead irrigation.
Leaf spot*
(Alternaria raphani)
Round to elongate, concentric, brown spots covered
with black, powdery spores. Spots are small at first,
then turn gray-green with water-soaked margins.
On growing stock, cruciferous plants, and crop refuse. Favored by wet weather. Spores are airborne. Also found on
other cruciferous crops.
Destroy all plant refuse by plowing under plants as soon as
flowers are harvested. Spray with a copper fungicide or mancozeb during wet weather. Avoid overhead irrigation.
Verticillium wilt*
(Verticillium dahliae)
Foliage yellows and wilts. Leaves die and dry progressively upward from the base of the plant. Dark discoloration may occur in the vascular system.
Soilborne as microsclerotia for many years. Symptoms
most severe when weather turns warm after a cool period.
Host range of this form of Verticillium is different from that
of the common Verticillium.
Avoid fields where disease has occurred or fumigate soil with
a chloropicrin or chloropicrin combination (tarped). This combination also controls most weeds, nematodes, soil insects,
and other fungi and bacteria.
Water mold root rots
Phytophthora spp.* and Pythium
spp.*)
Plants wilt easily or suddenly collapse. Roots and
crown become decayed. Also causes damping-off of
seedlings.
Soilborne pathogens. Associated with poorly drained, waterlogged soils. Spores are spread in water.
Provide drainage and avoid excessive irrigation. Plant on
raised beds. Seed treatments help to control the damping-off
phase. An oomycete (water mold) specific fungicide may also
be effective.
Continued on next page . . .
Disease Control Outlines
Stock (11/20)
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Stock, continued
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Mosaic
(several viruses, including Impatiens necrotic spot virus and Turnip mosaic virus)
Leaf mottling and flower breaking occur. Leaf symptoms vary with different viruses. White and yellow varieties do not show flower breaking.
In cruciferous weeds (mustard, wild radish, shepherd'spurse, etc.). Spread by aphids. Not seedborne. Symptoms
favored by cool weather.
Destroy nearby weeds. Avoid fields near uncontrolled weedy
areas. Plow under stock as soon as the crop is cut. Control
aphids.
Stock is also susceptible to downy mildew* (Peronospora parasitica).
* For additional information, see section on Key Diseases.
Disease Control Outlines
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STRAWFLOWER
Helichrysum bracteatum (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Downy mildew*
(Plasmopara halstedii and
Bremia lactucae)
Two distinct downy mildews infect strawflower, though
symptoms are similar for both diseases: yellow foliage
with downy white sporulation on the undersurface.
Leaves roll downward. Tissues sometimes are killed
Disease is favored by cool (59°F), wet weather. Spores
(sporangia) are airborne. Chilean tarweed (Madia sativa)
and other members of the family Compositae are hosts of
P. halstedii.
Control tarweed for some distance away if possible. Protective
fungicides should be effective but few if any are labeled for
strawflower.
Verticillium wilt*
(Verticillium dahliae)
Wilting and yellowing of lower leaves on one side of
plant. Vascular discoloration.
Favored by cool spring. Symptoms develop rapidly in hot
weather at flowering. Fungus survives in soil for long periods as microsclerotia. Many plants are infected including
weeds, crop plants, and ornamentals.
Avoid fields that are known to be infested. Soil fumigation with
chloropicrin or a chloropicrin combination is effective.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Aster yellows*
(Aster yellows phytoplasma)
Plants stunted and yellow. Frequently one-sided. Flowers may be green.
Aster yellows phytoplasma is spread by leafhoppers. A
wide variety of plants including weeds are susceptible.
Control weeds in and around planting. Leafhopper control may
help.
* For additional information, see section on Key Diseases.
Disease Control Outlines
Strawflower (11/20)
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SWEET PEA
Lathyrus odoratus (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Black root rot*
(Thielaviopsis basicola)
Poor top growth. Black lesions on roots and root rot.
Seedlings may be killed.
Fungus is soilborne. Favored by cool, wet soils and any
condition that weakens the plant.
Avoid fields previously planted in legumes. Avoid overirrigation
and overfertilization. Plant on raised beds.
Powdery mildew*
(Erysiphe trifolii)
White powdery growth on surface of leaves and stems.
Older infected leaves yellow and wither. Growth of
heavily infected plants is diminished.
Favored by moderate temperatures. Spores (conidia) are
produced in great abundance and they are airborne. Moisture is not necessary for germination and infection and is
detrimental to the fungus.
Several powdery mildew fungicides are effective if applied in a
regular preventative program commencing with the first signs
of the fungus. Check product label for registration.
Ramularia leaf spot
(Ramularia deusta)
Large, irregular or circular tan spots without definite
margins. Lower leaves are first affected. Infected
leaves often drop.
Fungus is specific to sweet pea and survives in sweet pea
refuse. Favored by wet conditions.
Rotate with other crops for 2 years. A fungicide may be necessary in some severe cases. Avoid overhead irrigation.
Seed decay
(Pythium spp. and other fungi)
Seeds rot in soil. Seedlings do not emerge.
Favored by wet soil and poor aeration.
Provide better drainage. Grow on raised beds.
Virus or viruslike disease
Symptoms
Host range and natural spread
Comments on control
Enation mosaic
(Pea enation mosaic virus)
Leaves contain scattered translucent areas ("windows"). Foliage may be crumbled and stunted. There
may be "windows" in the flowers.
Virus is spread by aphids. Host plants include many legumes.
Control nearby weeds, especially legumes. Control aphids.
Mosaic
(Pea mosaic virus)
Mottling and chlorosis of the foliage. Dark green areas
interspersed with yellow-green portions of leaves. Flowers have "broken" colors.
Virus is spread by aphids. Host plants include many legumes.
Control nearby weeds, especially legumes. Control aphids.
Spotted wilt
(Tomato spotted wilt virus)
Reddish brown streaks on stems. Leaves with circular
spots that are yellow at first and later turn brown. Plant
may die.
Spread by thrips. Virus has a wide host range, including
many weeds. Juvenile thrips (nymphs) acquire the virus
and transmit it as adults.
Control nearby weeds including grasses. Control thrips.
Sweet peas are also susceptible to Ascochyta blight (Ascochyta lathyri), bacterial streak (Pantoea agglomerans, formerly Erwinia herbicola), fasciation (Rhodococcus fascians), Pythium root rot* (Pythium spp.), cottony rot* (Sclerotinia sclerotiorum),
downy mildew* (Peronospora trifoliorum), and damping-off* (Rhizoctonia solani, Fusarium spp., and Pythium spp.)
* For additional information, see section on Key Diseases.
Disease Control Outlines
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SWEET WILLIAM
Dianthus barbatus (11/20)
Disease (causal agent)
Symptoms
Survival of pathogen and effect of environment
Comments on control
Fusarium wilt*
(Fusarium oxysporum
f. sp. dianthi)
Yellowing of new growth. Plants stunted and leaves
point downward instead of upward as in a healthy plant.
Leaves gradually turn yellow and die. The vascular system of the lower stem and roots is brown.
Fungus survives in soil for many years as chlamydospores. Disease is favored by warm soils and high temperatures.
Fumigate soil with chloropicrin or a chloropicrin combination.
Grow seedlings in heat-treated, solarized, or fumigated soil or
growing medium.
Leaf spot
(Cladosporium echinulatum)
Yellowish brown, withered spots surrounded by a purplish margin on leaves. As the disease progresses, entire leaves and stems become necrotic.
Spores (conidia) are airborne. Fungus survives on sweet
william debris. Favored by wet weather and overhead irrigation.
Avoid overhead irrigation. Protect foliage with a fungicide.
Sweet williams are also susceptible to rust* (Uromyces caryophyllinus and Puccinia arenariae), root rot* (Pythium ultimum), gray mold* (Botrytis cinerea), stem rot (Rhizoctonia solani), southern blight* (Sclerotium rolfsii), Septoria leafspot (Septoria
dianthi), anther smut (Microbotryum violaceum, formerly Ustilago violacea), curly top (Beet curly top virus), and aster yellows* (aster yellows phytoplasma).
* For additional information, see section on Key Diseases.
Disease Control Outlines
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Host-Pathogen Index
(11/20)
The host-pathogen index is a list of ornamental hosts not covered in the Disease Control Outlines and
some of the pathogens that attack these hosts. Diseases covered in Key Diseases are noted with an asterisk.
African Violet (Saintpaulia ionantha)
Bacterial blight
Foliar nematode**
Gray mold*
Phytophthora crown rot*
Powdery mildew*
Pythium root rot*
Rhizoctonia stem rot
Ring spot
Christmas cactus (Schlumbergera bridgesii)
Crown rot*
Fusarium rot*
Gray mold*
Root and stem rot
Root rot*
Stem rot
Stem rot and leaf spot
Virus
Candytuft (Iberis amara)
Alternaria leaf spot*
Dickeya (=Erwinia) chrysanthemi
Aphelenchoides ritzemabosi
Botrytis cinerea
Phytophthora parasitica
Odium spp.
Pythium spp.
Rhizoctonia solani
physiological (cold water and light)
Phytophthora parasitica
Pythium aphanidermatum
Fusarium oxysporum
Botrytis cinerea
Rhizoctonia solani
Pythium irregulare
Phytophthora spp.
Bipolaris cactivora
Cactus virus X
Alternaria brassicae
Basal stem rot
Phoma lingam
Club root
Plasmodiophora brassicae
Downy mildew*
Gray mold*
Phytophthora root rot*
Powdery mildew*
Pythium root rot*
Root knot nematode**
White rust
Peronospora parasitica
Botrytis cinerea
Phytophthora spp.
Erysiphe cruciferarum
Pythium spp.
Meloidogyne sp.
Albugo candida
Cineraria (Senecio cruentus)
Collar rot
Downy mildew*
Gray mold*
Impatiens necrotic spot
Leaf spot*
Powdery mildew*
Root and collar rot*
Root rot*
Spotted wilt
Stem rot*
*
For additional information, see section on Key Diseases.
*
*
For additional information, see section on Nematodes.
Rhizoctonia solani
Plasmopara halstedii
Botrytis cinerea
Impatiens necrotic spot virus
Alternaria cinerariae
Erysiphe cichoracearum
Sphaerotheca fuliginea
Phytophthora spp.
Pythium ultimum
Tomato spotted wilt virus
Sclerotinia sclerotiorum
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Gardenia (Gardenia jasminioides)
Bacterial leaf spot
Chlorosis
Petal blight (gray mold)*
Phomopsis canker
Root knot nematode**
Gerbera (Gerbera jamesonii)
Bacterial leaf spot*
Black root rot*
Crown and root rot
Gray mold*
Leaf spots
Phytophthora crown rot*
Powdery mildew*
Pythium root rot*
Sclerotinia crown rot
Spotted wilt
Verticillium wilt*
White rust***
German violet (Exacum affine)
Basal stem rot
Gray mold*
Root rot*
Spotted wilt
Gloxinia (Sinningia speciosa)
Cottony rot and flower blight*
Crown rot
Crown rot and tuber rot
Gray mold*
Ring spot
Root and crown rot*
Root rot*
Southern blight*
Spotted wilt
Hydrangea (Hydrangea macrophylla)
Gray mold*
Powdery mildew*
Rhizoctonia stem rot
Ringspot
Root knot nematode**
Root rot*
Virescens
*
**
**
*
Xanthomonas campestris pv. maculifoliigardeniae
iron deficiency
Botrytis cinerea
Phomopsis gardeniae
Meloidogyne spp.
Pseudomonas cichorii
Thielaviopsis basicola
Rhizoctonia solani
Botrytis cinerea
Alternaria porri
Cercospora gerberae
Septoria spp.
Ascochyta gerberae
Phytophthora cryptogea and others
Golovinomyces cichoracearum
Pythium spp.
Sclerotinia sclerotiorum
Tomato spotted wilt virus
Verticillium dahliae
Albugo tragoponis
Nectria hematocca
Botrytis cinerea
Pythium ultimum
Tomato spotted wilt virus
Sclerotinia sclerotiorum
Myrothecium roridum
Rhizoctonia solani
Botrytis cinerea
physiological (cold water and light)
Phytophthora cryptogea
P. nicotiana
Pythium spp.
Sclerotium rolfsii
Tomato spotted wilt virus
Botrytis cinerea
Golovinomyces orontii
Rhizoctonia solani
Hydrangea ringspot virus
Meloidogyne spp.
Pythium spp.
Phytoplasma
For additional information, see section on Key Diseases.
For additional information, see section on Nematodes.
Not reported in U.S.A.
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Impatiens (Impatiens walleriana)
Bacterial fasciation
Bacterial leaf spot*
Black root rot*
Brown crown canker
Crown rot*
Downy Mildew*
Gray mold*
Impatiens necrotic spot
Leaf spot
Root rot*
Southern blight*
Spotted wilt
Verticillium wilt*
Rhodococcus fascians
Pseudomonas syringae
Thielaviopsis basicola
Rhizoctonia solani
Pythium ultimum
Rhizoctonia solani
Plasmopara obducens
Botrytis cinerea
Impatiens necrotic spot virus
Phyllosticta sp.
Pythium sp.
Sclerotium rolfsii
Tomato spotted wilt virus
Verticillium dahliae
Kalanchoe (Kalanchoe blossfeldiana)
Aster yellows*
Edema
Fasciation
Impatiens necrotic spot
Kalanchoe mosaic
Leaf and stem blight
Leaf spots
Powdery mildew*
Root and crown rot*
Spotted wilt
Stem rot
Aster yellows phytoplasma
Physiological; cause unknown
Cercospora sp.
Impatiens necrotic spot virus
Kalanchoe mosaic virus
Botrytis cinerea*
Stemphylium spp.
Sphaerotheca fuliginea
Phytophthora spp.
Tomato spotted wilt virus
Myrothecium roridum
Lilac (Syringa vulgaris and S. persica)
Armillaria root rot*
Bacterial blight**
Crown gall*
Gray mold*
Leaf blotch
Phytophthora blight
Phytophthora root rot**
Powdery mildew*
Shoot blight*
Armillaria mellea
Pseudomonas syringae pv. syringae
Agrobacterium tumefaciens
Botrytis cinerea
Heterosporium syringae
Phytophthora spp.
Phytophthora spp.
Microsphaera penicillata
Sclerotinia sclerotiorum
Lilies (Lilium spp.)
Cottony rot and petal blight*
Foliar nematode*
Gray mold*
Leaf spots*
Root knot nematode
Rust*
Scale rots
Lisianthus (Eustoma grandiflora)
Foliar nematode**
Gray mold*
Leaf spot*
Powdery mildew*
Root knot nematode**
Root and stem rot
Sclerotinia sclerotiorum
Aphelenchoides spp.
Botrytis spp.
Cercospora, Heterosporium, and Ramularia
spp.
Meloidogyne spp.
Uromyces spp.
Colletotrichum spp.
Aphelenchoides spp.
Botrytis cinerea
Cercospora eustomae
Leveillula taurica
Meloidogyne spp.
Fusarium avenaceum, Phytophthora, Pythium,
and Rhizoctonia spp.
Host Pathogen Index (11/20)
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Viruses
Tomato spotted wilt virus, Impatiens necrotic
spot virus
Pouch Flower (Calceolaria x herbeohybrida)
Cottony rot*
Gray mold*
Root and crown rot*
Root rot*
Spotted wilt
Stem rot
Verticillium wilt*
Sclerotinia sclerotiorum
Botrytis cinerea
Phytophthora spp.
Pythium spp.
Tomato spotted wilt virus
Myrothecium sp.
Verticillium dahliae
Primula (Primula x polyantha)
Crown rot
Fasciation
Gray mold*
Leaf spot
Root rot*
Spotted wilt
Rhizoctonia solani
Physiological; cause unknown
Botrytis cinerea
Ramularia primulae
Pythium spp.
Tomato spotted wilt virus
Protea (Protea, Banksia, Leucospermum, and other spp.)
Canker
Botryosphaeria spp.
Gray mold*
Botrytis cinerea
Leaf spots
Colletotrichum spp., Mycosphaerella spp.
Root and crown rot*
Phytophthora spp., Rhizoctonia solani
Root knot nematode*
Meloidogyne spp.
Verticillium wilt*
Verticillium dahliae
Queen Anne’s Lace (Daucus carota)
Aster yellows
Bacterial blight*
Black root rot
Early blight*
Leaf blight*
Powdery mildew*
Root and stem rot
Root, crown, and stem rots*
Southern blight*
Tuber rot
Viruses
Ranunculus (Ranunculus spp.)
Aster yellows*
Bacterial blight*
Cottony rot*
Downy mildew*
Gray mold*
Leaf spots*
Powdery mildew*
Root rots*
Rust
Smut
Southern blight*
Viruses
Aster yellows phytoplasma
Xanthomonas campestris pv. carotae
Alternaria radicina
Cercospora carotae
Alternaria dauci
Erysiphe heraclei
Fusarium spp.
Phytophthora, Pythium, and Rhizoctonia spp.
Sclerotium rolfsii
Rhizopus spp.
Celery mosaic virus, Carrot motley dwarf virus
Aster yellows phytoplasma
Xanthomonas campestris pv. carotae
Sclerotinia sclerotiorum
Peronospora spp.
Botrytis cinerea
Ramularia spp.
Erysiphe polygoni
Pythium spp., Rhizoctonia solani
Puccinia spp.
Entyloma spp.
Sclerotium rolfsii
Tomato spotted wilt virus, Ranunculus mosaic
virus
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Stephanotis (Stephanotis floribunda)
Crown rot
Gray mold*
Powdery mildew*
Stem dieback
Virus
Sunflower (Helianthus sp.)
Aster yellows*
Charcoal rot
Cottony rot*
Downy mildew*
Gray mold*
Head rot
Leaf spots*
Powdery mildew*
Root and stem rot*
Rust*
Smut
Southern wilt*
Rhizoctonia solani
Botrytis cinerea
Oidium sp.
Glomerella cingulata
Impatiens necrotic spot virus, Tomato spotted
wilt virus
Aster yellows phytoplasma
Macrophomina phaseolina
Sclerotinia sclerotiorum
Plasmopara halstedii
Botrytis cinerea
Rhizopus oryzae
Alternaria, Cercospora, and Septoria spp.
Golovinomyces cichoracearum
Phytophthora sp.
Coleosporium, Puccinia, and Uromyces spp.
Entyloma calendulae
Sclerotium rolfsii
* For additional information see section on Key Diseases.
Host Pathogen Index (11/20)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Insects, Mites, and Other Invertebrates
(Section reviewed 3/09)
General Information
COMMON SIGNS AND SYMPTOMS ON PLANTS
DAMAGED BY PEST INSECTS, MITES, SLUGS, AND
SNAILS (ARTHROPODS) AND THE PROBABLE CAUSES
(3/21)
Symptoms
arthropod by-products
bleached, bronzed,
stippled, or yellowed foliage
chewed or tattered
blossoms or foliage
Insects and Mites
Causes
•
cast skins (translucent or whitish): aphids, leafhoppers, lace bugs, spider
mites
•
dark fecal specks: lace bugs, leafminer adults, plant bugs, shore fly adults,
thrips
•
flocculence (cottony, waxy material): adelgids, certain aphids, lerp psyllids,
mealybugs, certain scale insects, whiteflies
•
large excrement (frass) particles: caterpillars, leaf beetles
•
pale foam or spittle: spittlebugs
•
pitch masses: larvae of certain moths e.g., Sequoia pitch moth
•
pitch tubes: certain bark beetles (Scolytinae)
•
shiny trails or slime: fungus gnat larvae, slugs, snails
•
silken mats, tents, or webs or rolled leaves: leafrollers, tent caterpillars, webworms
•
sticky honeydew and blackish sooty mold: aphids, mealybugs, psyllids, soft
scales, whiteflies
•
eriophyid mites e.g., blister, bud, erineum, gall, or rust mites
•
lace bugs
•
leafhoppers
•
plant bugs
•
spider mites
•
thrips
•
adults and larvae of leaf-feeding beetles
•
crickets, grasshoppers, or katydids
•
larvae (caterpillars) of butterflies and moths (Lepidoptera) e.g., armyworms,
cabbage looper, cutworms, diamondback moth, European pepper moth (Dufo
moth)
•
larvae of sawflies (broad-waisted wasps) e.g., rose slugs
Common Signs and Symptoms on Plants Damaged by Pest Insects, Mites, Slugs,
and snails (Arthropods) and the Probable Causes (3/21)
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Symptoms
dieback of plant
parts
distortion of plant
parts
foliage mines
holes in stems, bark
or twigs
Causes
•
leafcutting bees, which are important pollinators and should not be killed.
Where these bees have been collecting material for their nests covering those
plants with cheesecloth or other screening prevents further damage. Place out
these barriers when leaf cutting is first observed or the time of year (late winter or spring) when damage first occurred during previous seasons. Barriers
can be removed about midsummer when the mother bees are no longer active.
•
snails or slugs e.g., brown garden snail
•
armored scales
•
gall wasps
•
katydids
•
larvae of boring beetles or moths
•
sharpshooters (large leafhoppers)
•
weevils
•
aphids
•
eriophyid or tarsonemid mites e.g., broad, cyclamen, blister, bud, erineum,
gall, or rust mites
•
gall wasps
•
larvae of certain moths
•
lygus bugs or stink bugs
•
other true bugs (Heteroptera)
•
psyllids
•
thrips
•
larvae of certain flies, moths, or sawflies (broad-waisted wasps)
•
adult beetles e.g., bark beetles, flatheaded borers, longhorned beetles
•
larvae of boring beetles or caterpillars (e.g., clearwing moths) feeding hidden
in plants
Adapted from Container Nursery Production and Business Management Manual, UC ANR Publ. 3540
Insects and Mites
Common Signs and Symptoms on Plants Damaged by Pest Insects, Mites, Slugs,
and snails (Arthropods) and the Probable Causes (3/21)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
MONITORING WITH STICKY TRAPS (3/21)
Trapping can be an efficient and informative monitoring tool. Traps can alert growers to pests early before
crop damage occurs and before pests become abundant and more difficult to control.
Yellow sticky traps
Yellow cards (commonly 3 × 5 inches or larger) covered on both sides with sticky material attract and capture the adults of various flying insects. Yellow sticky traps can indicate localized spots of high pest abundance or periods of migration of adult pests into crops and the predominant direction from which they are
arriving (e.g., from an adjacent field of drying weeds). Traps can also provide a relative measure of insect
abundance; comparisons of the number of adults caught among sample dates can indicate whether pest
density is decreasing, increasing, or remaining about the same over time. Pests captured by yellow sticky
traps include adults of fungus gnats, thrips, and whiteflies, aphids, psyllids, and sharpshooters. Others
presented side-by-side for comparison in Sticky Trap Monitoring of Insect Pests include leafminers, shore
flies, and adults of certain parasites and predators.
Blue sticky traps are sometimes used for thrips because this color is more attractive to thrips. However insects are more difficult to discern and count in blue traps. Yellow sticky traps attract a wider variety of
pest insects and are recommended for most situations.
Sticky traps may not be a good tool for deciding treatment need, whether any action thresholds are exceeded (see ESTABLISHING ACTION THRESHOLDS), and they are generally not effective for direct control. Immature stages feeding on crops commonly cause the most damage; sticky traps typically capture
only airborne adults, which in many species do not feed on plants. Adult trapping sometimes is not a reliable indicator of pest presence or abundance on the crop. Many of the trapped adults may be migrating
species that don't feed on the crops being grown. Adults often cannot readily be discriminated to species;
for example, the adults can obviously be aphids but whether they are aphid species that infest the crops
present may not be discernable from specimens stuck in sticky material. Always use traps in combination
with visual inspection of plants for the presence of damage and pest feeding stages.
Unless other guidelines are recommended use at least one sticky trap per 10,000 sq. ft. of growing area.
When monitoring whiteflies, use about one trap per 1,000 sq. ft. of growing area with crops susceptible to
infestation. Actual trap density will be dictated by the growing area and the time and effort devoted to
trapping. But each pest management unit should have at least one, well-maintained, yellow sticky trap. In
addition, put one trap inside growing areas by doors and vents to detect pests migrating in. Also put at
least one trap in each crop that is very susceptible to damage by pests and do not locate the most pest-susceptible crops near doors. Use bright yellow traps, each 3 × 5 inches or larger and covered with sticky material.
Orienting traps horizontally (facing the soil or upwards) is sometimes recommended when monitoring
pests such as fungus gnats and shore flies that emerge from or rest upon growing media. However, to
catch a wider range of targeted insects, orient the longest part of the trap vertically (up and down). Place
each trap so that its bottom is even with the top of the plant canopy. For rapidly growing crops, locate trap
bottoms a few inches above the canopy so that the plants do not soon overgrow the traps. As plants grow,
move each trap up so that its bottom remains about even with the top of the canopy or somewhat higher.
For example use one or two clothespins to attach each trap to a bamboo post or wooden dowel embedded
in the growing media or a stand. Alternatively hang traps from rafters or wires strung between posts.
Number each trap and map its location in your growing area. Inspect each trap at least once or twice
weekly. It is easiest to replace traps each time you inspect them. Wrap traps in clear plastic film and take
them to a more comfortable location for counting. Alternatively replace traps when they become too
fouled to effectively capture insects or count them quickly. If traps are reused, note this because catches
become cumulative; you must subtract the number of insects present the last time that particular trap was
checked, or sum and average the counts from all traps in a specific growing area then subtract the previous average from that currently.
Count and record the number of each type of pest caught. When abundant it is not necessary to count all
insects on the entire trap; counting the insects in a vertical column 1 inch wide on both sides of the trap,
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then multiplying the results by the trap width in inches, gives results that are representative of the entire
trap. Do not reduce traps to 1 inch vertical strips because smaller traps will be less attractive to insects.
Waterless hand cleaner can be useful for removing the sticky material from hands.
Because many insects in traps may be beneficial or harmless, carefully identify insects before taking management actions. High-quality color photographs and line drawings of commonly trapped insects are
available in Sticky Trap Monitoring of Insect Pests. You can also wrap used traps in clear plastic and take
those containing unknown insects to offices of the UC ANR Cooperative Extension or county agricultural
commissioner for help in identification.
Interpreting Information from Yellow Sticky Traps
Regularly summarize trap data to facilitate comparison. For example, graph the average numbers of each
pest in all traps from a particular growing area on each sample date. This allows visual recognition of
trends in pest abundance and facilitates comparison to stages of crop growth and when particular management actions were taken.
Interpreting trap information requires knowledge, skill, and practice. Traps catch both migrating insects as
well as adults that emerged from the crop. Canopy density, plant foliage quality, and temperature influence adults' tendency to fly. Wind and ventilation fans can discourage flight, reducing trap catches. The
number of adults trapped may temporarily drop after a pesticide application even if there has been relatively little change in immature abundance on plants. Conversely, adult numbers of some species may
temporarily increase in traps after applying an adulticide, so the numbers caught for several days after an
application might not be best when comparing adult densities among sample dates.
Foliage disturbances, such as sprinkling with water (overhead irrigation) or shaking plants to promote
pollination or monitor adults (e.g., of whiteflies), increase trap catches. Even large numbers of pest species
in traps do not necessarily indicate that control action is needed. Always use traps in combination with
plant inspection to determine whether economically damaging numbers of pests and stages susceptible to
control actions are present. For more information, see ESTABLISHING ACTION THRESHOLDS.
Sticky Tape Traps
Crawlers, the mobile first instars of certain Sternorrhyncha (formerly Homoptera), are the life stage most
susceptible to many pesticides. Traps made of double-sided clear sticky tape (available at stationery stores)
are an efficient method of monitoring crawlers of armored scales, foliar-feeding mealybugs, soft scale insects, and certain other arthropods. On each of several plants infested with adult females, snugly wrap a
stem with tape. Double over the loose end of the tape several times so you can pull the end to easily unwind it. Place a tag or flag near each tape so you can readily find each tape trap. Change the tapes at regular intervals, about weekly. After removing the old tape, wrap the stem at the same location with fresh
tape. Preserve the old sticky tapes by sandwiching each tape unrolled between a sheet of pale-colored or
white paper and a sheet of clear plastic. Label the tapes with the collection date, location, and host plant.
Crawlers get stuck on the tapes and appear as yellow or orange specks. Examine the tapes with a hand
lens to distinguish the crawlers (which are round or oblong, have very short appendages, and may have
two dark eye spots) from contaminants such as dust, pollen, and spider mites. A contact insecticide and
certain other pesticide types can be applied when crawlers are abundant. If a single application is planned,
visually compare the tapes collected on each sample date. The best time for a single spray is after a sharp
increase in crawlers in traps or soon after crawler numbers have peaked and begun to decline.
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ESTABLISHING ACTION THRESHOLDS (3/21)
The presence of a few pest insects or mites and some amount of arthropod damage commonly is unavoidable and can be tolerated. The number of pests or level of damage beyond which management action
should be taken is known as the action threshold, a fundamental concept in integrated pest management.
When management action should be taken (when a threshold is exceeded) is determined by the total cost
of the action (including monitoring), the value of the crop, and the impact on the environment. Few
thresholds have been established for flower and nursery crops, in part because of the lack of research in
comparison with the large number of crop plants, pests, and growing situations. Specific thresholds or
management action guidelines may be developed over the long term by growers who regularly monitor
crops, keep good records, and evaluate and summarize outcomes for comparison over time. Consult the
chapters "Integrated Pest Management" and "Insects, Mites, and Other Pests" in the Container Nursery Production and Business Management Manual and also Integrated Pest Management for Floriculture and Nurseries
for more discussion and illustration of these techniques.
Why Use Thresholds
Pesticides sometimes are applied on a calendar schedule, when pest presence is only suspected, or when
pest numbers are already high and difficult to control. Using thresholds can maintain or improve crop
quality while reducing the cost and frequency of control measures. Less frequent applications help maintain pesticide efficacy by reducing the development of pesticide resistance. Fewer applications reduce the
disruptions to cultural practices that occur during applications and the subsequent restricted entry interval
(REI). In addition, fewer applications may improve plant growth and quality by minimizing phytotoxicity
and increase profit by reducing costs of pesticide purchases, application labor, and regulatory compliance.
When to Take Management Action
Because crops are grown for profit, action thresholds are based largely on economics. Management action
is warranted when the increased revenue expected from improved crop quality or yield will exceed the
cost and adverse impacts (such as phytotoxicity, harvest disruption) of the action. The amount of pest
damage or presence that can be economically tolerated is determined by many factors, including the type
of pest and damage, crop species and cultivar, stage of plant development, time until harvest or sale, and
market conditions. Tolerance to pests can be higher if infested plant parts are not marketed, such as older
leaves on seed crops or cut flowers. Thresholds can often be higher if highly effective or quick-acting
methods are available for controlling the problem. Conversely, if available controls are slow-acting or only
partially effective, or crops are of an exceptionally high value, thresholds may be relatively low. In certain
situations, regulations such as quarantines may impose zero tolerance for exotic organisms even when
numbers are low or an organism does not directly damage the marketed crop.
Mother stock and new plants should have virtually no pests. If pests are present at the beginning of the
production cycle, many arthropods can develop through multiple generations resulting in large populations before plants are shipped. Abundant pests on young plants may require repeated management actions and greatly increase the likelihood of damaged, poor-quality plants.
Action thresholds may be higher for mature plants of certain crops. More mature plants are often better
able to tolerate some level of certain types of pests or their damage. It is unlikely that susceptible crops can
always be maintained pest-free throughout their production cycle. As crops mature, they may be increasingly likely to become infested and are often more difficult to treat effectively because of the risk of phytotoxicity to colored bracts or flowers, increased difficulty in achieving good spray coverage on larger plants,
and pesticide reentry intervals relative to crop harvest or shipping.
If monitoring reveals very low pest abundance or damage near the end of production, it may not be necessary to take management actions because there may be insufficient time for populations to develop to
problem levels before the crop is sold.
How to Establish Thresholds
Establish thresholds by regularly monitoring plants in a consistent and systematic manner. Keep good records and judge the acceptability of the finished crop in comparison with records of pest monitoring and
management actions and the price received for the crop. Experiment over time to develop thresholds
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appropriate for your situation and market conditions. Be flexible in adjusting thresholds and adapt monitoring and management methods as appropriate.
Thresholds should be quantitative or numerical to be useful. For example, thresholds could be based on
the
• average number of pests per trap each week
• percent of leaves or plants found to be damaged or infested during visual inspection
• number of pests dislodged per beat or shake sample
Quantitative thresholds can be developed for most pest monitoring methods, such as treating when certain conditions are conducive to disease development or when invertebrate pests or damaged plant parts
exceed specified numbers or percentages. For example, management action may be warranted for whiteflies early in production when more than about 5 adults per trap per week are captured on one well-maintained 3-by-5-inch yellow sticky trap deployed per 1,000 sq. ft. of production. Thresholds for your situations may be very different.
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BIOLOGICAL CONTROL (3/21)
Biological control is the beneficial action of parasites (technically parasitoids), pathogens, and predators
in managing pests and preventing or reducing their damage. Biocontrol provided by these living organisms called “natural enemies” is especially important for reducing the abundance of pest insects and
mites and their damage to crops.
Conservation
Preserve resident natural enemies by choosing cultural, mechanical, and selective chemical controls that
do not kill these species or disrupt their beneficial activities. Many insect and mite pests in flower and
nursery crops have natural enemies that can keep their populations below economically damaging levels.
Conservation is the primary way to successfully use biological control. For example, using selective pesticides that do not kill natural enemies or disrupt their beneficial activities is a key component of integrated
pest management.
To enhance the effectiveness of biological control
• Consult the Natural Enemies Gallery to become familiar with common and important parasites and
predators of pests.
• Control ants, which protect some pests from parasites and predators.
• Exclude pests (e.g., bring only pest-free plants into growing areas, screen greenhouses) and use
excellent sanitation (e.g., promptly remove infested crop debris and eliminate weeds and other
nearby noncrop hosts of pests). These methods provide direct control and reduce or prevent the
in-migration of abundant pests that can overwhelm the potential effectiveness of natural enemies
that are resident or released.
• Grow flowering insectary plants in or near outdoor nurseries to provide nectar and pollen to feed
adult parasites and predators. Grow a series of plants that flower sequentially so blossoms are
available throughout the growing season. Ideal insectary plants are those that can also be marketed, such as for culinary herbs and cut flowers. Avoid insectary-plant species that host arthropod pests or plant pathogens that can move to damage nearby crops. Consult Flowers; Fruit Trees,
Nuts, Berries, and Grapevines; Trees and Shrubs; and Vegetables and Melons for lists of the pests reported on these plants.
• Keep growing areas and plants clean and free of dust, which can impede parasites’ and predators’ ability to locate and attack prey.
• Minimize or avoid the application of broad-spectrum, persistent (long-residual) acaricides and
insecticides.
• Rely on pesticides that do not kill natural enemies or disrupt their beneficial activities where this
is feasible.
• When pesticides are used, apply them in a selective manner. For example, spray only the more
heavily infested portions of the crop (hot spots) and where needed to prevent crop damage. Conserving resident natural enemies elsewhere in the unsprayed growing area allows parasites and
predators to reproduce and the adults to disperse and attack pests elsewhere in growing areas
where the plant-feeding species are not currently abundant or causing noticeable damage.
Augmentation
When the desired natural enemies are not present, or they are not abundant enough to sufficiently reduce
pest numbers, biological control can sometimes be augmented with the purchase and release of commercially reared natural enemies. Augmentative releases can be inoculative or inundative. As discussed below and in more detail in Natural Enemy Releases for Biological Control of Crop Pests, there are various release strategies (e.g., banker plants discussed below). Be aware that in most situations, employing practices that conserve resident natural enemies is more effective and less expensive and time consuming
than purchasing and releasing them.
Inoculative release
When pest populations are low, relatively few natural enemies may be needed for effective release. The
introduced parasites or predators are expected to reproduce, and it is their progeny that are expected to
provide biological control. Releasing the mealybug destroyer lady beetle (Cryptolaemus montrouzieri) in
late winter or spring to control foliar-feeding mealybugs is an example of inoculative release. The lady
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beetle is a highly effective predator of mealybug species that lay eggs in a cottony mass (ovisac). But this
predator is native to the semi-tropics and does not survive cold weather, so to be effective it must be purchased and released early each growing season where mealybugs have been a problem. A parasitic wasp,
Leptomastix dactylopii, can be released to kill nymphs of citrus mealybug. The mealybug destroyer and
Leptomastix dactylopii parasite can be released in combination where citrus mealybug is a pest.
Inundative release
When releasing large numbers of natural enemies, often several times over a growing season, the individuals released are expected to provide biological control. Periodically releasing Trichogramma spp. egg parasitic wasps to destroy moth eggs is an example of inundative biological control. Trichogramma releases to
kill moth eggs are compatible with applying Bacillus thuringiensis (Bt) to control the caterpillar stages and
drenching soil with entomopathogenic nematodes (Heterorhabditis and Steinernema spp.) to kill the soildwelling, mature larvae and pupae of armyworms, cutworms, and European pepper moth (Dufo moth).
Periodically releasing large numbers of convergent lady beetles (Hippodamia convergens) to temporarily
control aphids is also inundative release. Each convergent lady beetle can consume several dozen aphids
per day. Because the beetles will virtually all disperse within 1 or 2 days of being released, and generally
will lay few eggs and not reproduce in the crop, releases must be repeated about weekly to provide control where aphids are an ongoing problem. Because the purchased beetles are field collected from mountainous foothills during their overwintering (diapause) phase, when collected, transported, and released,
the convergent lady beetles are physiologically obliged to fly and disperse before settling to lay eggs
among aphids. For more information, see Lady Beetle Releases for Aphid Control: How to Help Them Work
(PDF ) from the newsletter UC IPM Retail Nursery and Garden Center IPM News.
Banker plants
One strategy for releases is to maintain natural enemies by rearing them on alternative insects that are not
pests of the desirable crops. For example, barley, oats, or wheat infested with bird cherry-oat aphid might
be used to maintain Aphidius colemani parasitic wasps in the greenhouse. This aphid is not a pest of many
greenhouse bedding plants, but the wasps will feed on many other kinds of aphids (like green peach
aphid) that are pests. These banker plants (e.g., planted in containers) with nonpest aphids and parasites
or predators can be scattered throughout a greenhouse or nursery to provide a continual source of natural enemies that disperse to consume pest species on crops, such as for aphid control in greenhouses
(PDF).
Effectiveness of releases
Augmentation is likely to be effective only in situations where researchers or other pest managers have
previously demonstrated success. Guidelines for releasing natural enemies are provided in this publication in the sections on aphids, foliar-feeding mealybugs, fungus gnats, twospotted spider mite, and
whiteflies.
Because natural enemies are living organisms, they require food (adults of many species require nectar
and pollen), shelter from harsh conditions, suitable environmental conditions, and water. Natural enemies may be adversely affected by low humidity or extreme conditions such as hot temperatures. Residues of certain pesticides can persist for weeks or months, harming natural enemies long after losing
their effectiveness against pest species. Many beneficial species stop reproducing under short day length
or prolonged cool conditions; supplemental light may be necessary for them to reproduce and be effective year-round. Environmental conditions required by natural enemies (such as long days) may not be
compatible with production needs of certain crops.
Desperate situations where pests are already abundant or damaging are not good opportunities for augmentation. Because pest presence is necessary to sustain natural enemies, choose crops where some levels
of the target pests and their feeding can be tolerated (crops with moderate to high pest thresholds). Begin
making releases early in the production cycle even before infestations are observed. Consider what other
pests may occur in the crop and how they can be managed in ways that are compatible with conserving
natural enemies. For more information, see Natural Enemies Handbook: The Illustrated Guide to Biological
Pest Control, UC ANR 3386 (print edition), 9038 (ePub); and Natural Enemy Releases for Biological Control of
Crop Pests.
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Insect, Mite, and Other Invertebrate Management
(Section reviewed 3/09)
APHIDS (05/10)
Melon aphid: Aphis gossypii
Green peach aphid: Myzus persicae
DESCRIPTION OF THE PESTS
Aphids are distinguished from other insects by the presence of cornicles, tubelike appendages that protrude from the rear of the aphid. Numerous species of aphids attack California ornamental crops, but the
two species most commonly encountered are the green peach aphid and the cotton or melon aphid.
Melon aphids are typically dark green, but color variations do occur frequently. The cornicles are relatively short, stout, and always dark. Melon aphids have red eyes and antennae that only reach to the middle of the abdomen. Green peach aphid is characterized by a depression in the front of the head between
the antennae (best seen with the use of a hand lens) and by long thin, translucent cornicles that extend
beyond the tip of the body. Green peach aphids vary in color from yellowish green to rose pink. Winged
adults have a dark blotch in the middle of the abdomen.
Adult aphids may or may not have wings. Winged aphids are produced as a result of crowding. Green
peach aphids produce winged adults at lower population densities than the melon aphid. The optimal
temperature for green peach aphid development is 75°F, whereas optimal temperatures for development
of melon aphids are above 75°F.
Adult aphids give birth to live young. Generally, aphids begin giving birth when they are 7 to 10 days
old, depending on temperature.
DAMAGE
Aphids excrete copious amounts of honeydew, a sweet, sticky substance that they produce as they feed
on the plants. The honeydew can cover leaves and other plant parts and cause the plants to become
sticky. Black sooty molds then grow on the honeydew. The white shed skins of the aphids frequently are
stuck to the plant surfaces by the honeydew and further detract from the plant's appearance. Sufficient
feeding can cause foliage to become yellowed, and feeding on newly developing tissues can cause those
parts to become twisted as they grow. Melon aphids are known to transmit 44 plant viruses, while green
peach aphids are known to transmit more than 100 plant viruses.
MANAGEMENT
Biological Control
Predators such as lacewings (Chrysoperla spp.) and midges (Aphidoletes aphidimyza) are commercially
available. Parasites, such as Aphidius spp., Lysiphlebus testaceipes, Diaeretiella rapae, and Aphelinus abdominalis, are also commercially available. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because aphids feed on a large variety of plant species, keep production areas free of weeds, which can
serve as hosts of aphid populations. Exclusion of winged adults can be accomplished by covering openings to the greenhouse with screens that have a pore width of 355 microns or smaller. Before starting a
new crop, carefully inspect plants to ensure that they are free of aphids and other pests. Treat or rogue
any infested plants.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture winged adults. However, aphids produce winged
individuals in response to crowding so monitoring plants for infestations is an essential component of
managing and detecting these pests before populations get too high. Melon aphids tend to have a more
uniform vertical distribution on plants than green peach aphids, which tends to be clustered around
growing points, meaning that infestations of melon aphids under lower leaves can easily go undetected if
these areas are not inspected. Green peach aphids will produce winged individuals at lower densities
than melon aphids on crops such as chrysanthemums. Use at least one sticky trap per 10,000 square feet
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(900 sq m) of growing area for monitoring aphids. For more information, see MONITORING WITH
STICKY TRAPS.
Consider treating if an average of 5 to 10 aphids per card per week is present.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
biological
botanical
carbamate
Pesticide
(trade name)
A. Beauveria bassiana#
(BotaniGard 22 WP)
(BotaniGard ES)
Laverlam
A. cinnamaldehyde
(Cinnacure)
oil4
REI1
Mode of
action 2 Comments
4
—
4
—
Proguard
4
—
B. pyrethrin/PBO3
(PT Pyrethrum TR)
Whitmire MicroGen
12
3
A. methiocarb*
(Mesurol 75W)
Gowan
24
1A
Apply in 50 gal water. Repeat as necessary
up to 2 applications/season. Do not apply
with oil or foliar fertilizer.
OHP
4
un
B. azadirachtin
(Ornazin 3%EC)
C. pyriproxyfen
(Distance)
D. s-kinoprene
(Enstar II)
SePRO
12
un
Must contact insect. Repeat applications as
necessary. Aphid suppression only. Label
permits low-volume application.
Do not exceed 22.5 oz/acre/application.
Valent
12
7C
Wellmark
4
—
A. imidacloprid
(Marathon 1G)
(Marathon II)
OHP
12
4A
B. imidacloprid
(Marathon 60 WP)
OHP
12
4A
A. clarified hydrophobic ex- OHP
tract of neem oil#
(Triact 70)
4
un
insect growth regu-A. azadirachtin
lator
(Azatin XL)
neonicotinoid
Manufacturer
Treat every 7 days while insects are active.
Do not tank mix with most fungicides and
wait 48 hours after application to apply a
fungicide.
Do not apply to stressed plants or newly
transplanted material before roots are established.
An aerosol.
Do not apply more than 2 times per cropping cycle or per 6 months.
Apply prebloom. Also labeled for low volume use.
Not to be used more than once every 16
weeks. Do not apply to soils that are water
logged or saturated. Do not apply to bedding plants intended to be used as food
crops.
As above, but apply only as a drench.
Do not spray plants under stress. Target
pest must be completely covered with
spray—this material may not effectively
control melon aphid because it is often on
the underside of lower leaves. Check label
for list of plants that can be treated. May
cause injury to flowers.
Continued on next page . . .
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Treatment, continued
Class
oil4
cont.
Pesticide
(trade name)
B. horticultural oil5
(Ultra-Fine Oil)
pyridine
Whitmire MicroGen
Brandt
JMS Farms
United Phosphorus
REI1
Mode of
action2 Comments
Use as above for neem oil. Also, do not use
with sulfur fungicides; check label for tank
mix restrictions.
12
—
4
4
24
—
—
1B
B. acephate
Valent
(Orthene T, T&O Spray)
24
1B
C. acephate
(PT 1300 Orthene TR)
Whitmire MicroGen
24
1B
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
C. cyfluthrin
(Decathlon 20 WP)
D. deltamethrin*
(DeltaGard)
E. fenpropathrin*
(Tame 2.4 EC)
F. fluvalinate
(Mavrik Aquaflow)
G. lambda-cyhalothrin*
(Scimitar)
Whitmire MicroGen
FMC
12
3
12
3
Check label. A fogger for greenhouse use
only.
Label permits low-volume application.
OHP
12
3
Label permits low-volume application.
Bayer
12
3
Valent
24
3
Label permits low-volume application.
Wellmark
12
3
Syngenta
24
3
H. permethrin
(Astro)
FMC
12
3
Label permits low-volume application. Also
labeled as a cutting dip at 5 fl oz/100 gal.
For greenhouse and nursery use. Apply at
7-day intervals. Do not apply more than
52.4 fl oz of concentrate/acre/year. Do not
mix with EC formulations or oils.
Direct application to blooms may cause
browning of petals. Marginal leaf burn may
occur on salvia, dieffenbachia and pteris
fern. Label permits low-volume application.
Do not apply more than 2 lb a.i./acre/year.
A. pymetrozine
(Endeavor)
Syngenta
12
9B
(SafTSide)
(JMS Stylet Oil)
organophosphate A. acephate
(Acephate 97UP)
pyrethroid6
Manufacturer
A number of chrysanthemum varieties have
exhibited phytotoxic reactions. Only labeled
for use on anthurium, cacti, carnation, rose,
orchids, some foliage plants, young poinsettia and some varieties of chrysanthemum. Can stunt new growth in roses.
An aerosol that is only for greenhouse use.
Apply as foliar spray at 7-14 day intervals.
For outdoor use, do not apply more than 48
oz/acre/year; for indoor use, do not use
more than 100 oz.
Continued on next page . . .
Major Insect and Mite Pests
Aphids (5/10)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Treatment, continued
Class
soap4
1
2
Pesticide
(trade name)
A. potash soap#
(M-Pede)
Manufacturer
Dow Agro
Sciences
REI1
12
Mode of
action2 Comments
—
Must contact insect, so thorough coverage
is important. Repeat weekly as needed up
to 3 times. Test for phytotoxicity. Do not
spray new transplants or newly rooted cuttings. Do not add adjuvants.
Restricted entry interval (REI is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://irac-online.org/.
3
PBO = piperonyl butoxide
4
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
5
Check with certifier to determine which products are organically acceptable.
6
Pyrethroids are generally not effective against green peach aphid.
*
Restricted use material. Permit required for purchase or use.
— Unknown.
#
Acceptable for use on organically grown ornamentals.
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
ARMORED SCALES (5/10)
Oystershell scale: Lepidosaphes ulmi
Greedy scale: Hemiberlesia rapax
California red scale: Aonidiella aurantii
Oleander scale: Aspidiotus nerii
San Jose scale: Diaspidiotus (=Quadraspidiotus) perniciosus
DESCRIPTION OF THE PESTS
The protective covering over armored scales is produced by molted skins and secretions from the scale.
Unlike soft scales, the protective covering can be lifted off the body of the armored scale. High populations of these sucking insects give plant stems a crusty appearance. The first nymphal instar is called a
crawler and has functional legs, while the remaining instars are attached to the leaf and do not move. Unlike soft scales, armored scales do not produce honeydew. Most armored scales have several generations
a year.
DAMAGE
Along with the unsightly encrustations that are the bodies of the immobile scales, these scales inject toxic
saliva that causes plants to decline.
MANAGEMENT
Biological Control
Aphytis melinus is a commercially available parasite that is effective in controlling California red scale. For
more information, see BIOLOGICAL CONTROL.
Cultural Control
Prune out and discard heavily infested plant parts. Exclusion of windblown crawlers can be accomplished by covering openings to the greenhouse with fine mesh screens.
Monitoring and Treatment Decisions
Carefully inspect new plants being brought into the production area to ensure that they are free of scales
and other pests. Treat infested plants.
Visual inspection of plants will help locate infestations and may permit localized treatments of hot spots.
Treatment is generally warranted when scales are present. Optimum treatment timing is when crawlers
are active; however, when there are overlapping, multiple generations, crawlers may emerge over a
lengthy time, making multiple applications necessary.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Pesticide
(trade name)
A. pyrethrin+PBO3
(PT Pyrethrum TR)
insect growth regu-A. pyriproxyfen
lator
(Distance)
Class
botanical
B. s-kinoprene
(Enstar II)
Manufacturer
Whitmire
MicroGen
Valent
Wellmark
REI1
12
Mode of
action2 Comments
3/—
An aerosol.
12
3
4
7A
Do not apply more than 2 times per cropping cycle or per 6 months. Do not use
through any type of irrigation system in
California.
Apply prebloom. Also labeled for low volume use.
Continued on next page . . .
Major Insect and Mite Pests
Armored Scales (5/10)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Treatment, continued
Class
oil4
Pesticide
(trade name)
Manufacturer
A. clarified hydrophobic ex- OHP
tract of neem oil#
(Triact 70)
B. horticultural oil5
(Ultra-Fine Oil)
12
United
Phosphorus
Valent
24
1B
24
1B
C. acephate
(PT 1300 Orthene TR)
D. malathion
(various)
Whitmire MicroGen
various
24
1B
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouses only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia, and
some varieties of chrysanthemum. Can
stunt new growth in roses. Do not use
through any type of irrigation system.
An aerosol for greenhouse use only.
12
1B
Not for greenhouse use.
A. cyfluthrin
(Decathlon 20WP)
B. fluvalinate
(Mavrik Aquaflow)
OHP
12
3
Label permits low-volume application.
Wellmark
12
3
Label permits low-volume application. Also
labeled as a cutting dip at 5 fl oz/100 gal.
organophosphate A. acephate
(Acephate 97UP)
B. acephate
(Orthene T,
T&O Spray)
1
2
Mode of
action2 Comments
un
Do not spray plants under stress. Target
pest must be completely contacted with
spray. Check label for list of plants that can
be treated. May cause injury to flowers.
Use as above for neem oil. Also, do not
—
use with sulfur fungicides; check label for
tank mix restrictions.
—
—
Whitmire
MicroGen
Brandt
JMS Farms
(Saf-T-Side)
(JMS Stylet Oil)
pyrethroid
REI1
4
4
4
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://irac-online.org/.
3
PBO = piperonyl butoxide
4
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
5
Check with certifier to determine which products are organically acceptable.
*
Restricted use material. Permit required for purchase or use.
Acceptable for use on organically grown ornamentals.
#
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Armored Scales (5/10)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
ARMYWORMS AND CUTWORMS (5/10)
Beet armyworm: Spodoptera exigua
Variegated cutworm: Peridroma saucia
Yellowstriped armyworm: Spodoptera ornithogalli
DESCRIPTIONS OF THE PESTS
Beet armyworm
Beet armyworm is the most frequently encountered of the three species listed above. Adults are heavy
bodied moths (wingspread is about 1 inch, or 25–28 mm) with a characteristic mustard or orange colored
liver-shaped spot on the forewings that is narrowly ringed with white. The female lays egg masses on the
undersides of leaves, covering the eggs with felt made from her body hairs. The first through third instar
larvae often feed gregariously, skeletonizing the undersides of leaves, or they feed on the insides of buds.
Later instar larvae disperse and feed individually, chewing entirely through leaves or flowers. Early instar larvae are small and green, while late instar larval color may be green, brown, black, or gray. In all
instars, there are fine lines along the length of the body, with a more conspicuous lateral stripe and a
black spot just dorsal to the lateral stripe behind the head.
Degree-days
Calculate degree-days for beet armyworm in your location.
Learn to use video presentation degree-days to time insecticide applications.
Beet armyworm continually develops during winter in mild areas and builds up on weeds and in cotton,
lettuce, and tomato fields. One generation can take as little as 31 days at 75°F or 24 days at 80°F. Egg to
adult generation times can be calculated using degree-days (DD) based on a lower developmental temperature of 54°F. The egg stage requires the accumulation of about 94 DD from the time they are first laid
until egg hatch. The larval and pupal stages require the accumulation of 470 DD and 318 DD respectively
for females and 540 DD and 344 DD for males.
Yellowstriped armyworm
The yellowstriped armyworm larvae have a pair of black triangles on the back of most segments. Some
larvae appear nearly completely black when viewed from above. The lateral stripe is bright orange or yellow. The adult has a complex and highly contrasting pattern of brown, yellow, and white on the front
wings, and wingspread measure is about 1.5 inches.
Variegated cutworm
The variegated cutworm overwinters as a naked pupa in the soil. Adults have a distinct liver-shaped outline on the front wings and their wingspread can measure from 1.5 inches to a little over 2 inches. Larvae
have yellow or orange spots or a broken longitudinal stripe at the top of the body, which is otherwise
gray. Often there is a dark triangle or W-shaped mark on the top of the eighth body segment.
DAMAGE
Armyworms and cutworms mostly are a concern because they directly damage flowers as well as leaves
that would normally be marketed with the flowers. Presence of late-instar larvae in seedling flats can also
cause tremendous plant loss. On the other hand, moderate early-season feeding by armyworms on gypsophila may actually increase tillering and yields.
MANAGEMENT
Biological Control
A number of parasites, both tachinid flies and parasitic wasps, attack Lepidoptera larvae and reduce their
population growth rate. However, even if armyworm or cutworm larvae are parasitized, they continue
feeding through to the last instar and still damage crops. Viruses also do not usually kill the larvae until
later instars. Applying insecticides other than Bacillus thuringiensis (Bt) products are likely to exclude parasites because their residues are lethal to these beneficial insects. For more information, see BIOLOGICAL
CONTROL.
Cultural Control
Because these pests feed on a large variety of plant species, keep production areas free of weeds, many of
which serve as hosts to armyworms and cutworms. Exclusion of winged adults can be accomplished by
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covering openings to the greenhouses with screens. Screens are especially important when lights are used
at night in greenhouses to control flowering because lights attract moths. Individual seedling flats may
also be covered with screens to exclude adults and larvae. Row covers can be a practical measure to exclude moths in field production as long as the mesh prevents entry of adults and the row cover is held
above the plant surface to eliminate oviposition (egg laying) through the fabric.
Monitoring and Treatment Decisions
If Bt sprays are planned, use pheromone traps to determine adult flight activity and mating. Once adults
are caught in traps, it is very likely that larvae are present and Bt should be applied as soon as possible
because it is most effective against young larvae. Use regular visual inspections of plants to detect larvae
and their damage. For guidelines on when to treat, see ESTABLISHING ACTION THRESHOLDS.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
biological
botanical
Pesticide
(trade name)
A. Bacillus thuringiensis
ssp. kurstaki#
(various products)
A. pyrethrin+PBO3
(PT Pyrethrum TR)
A. carbaryl*
Manufacturer
Valent
REI1
4
Mode of
action2 Comments
11
Most effective against early instar larvae;
pheromone trapping recommended for
timing applications.
Whitmire MicroGen
Bayer
12
3/—
12
1A
OHP
4
un
Chemtura
12
15
Chemtura
12
15
D. tebufenozide
Dow Agro
(Mimic)
Sciences
organophosphate A. acephate
Valent
(Orthene T, T&O Spray)
4
18
24
1B
Whitmire MicroGen
Whitmire MicroGen
FMC
24
1B
12
3
12
3
Check label. A fogger for greenhouse use
only.
Label permits low-volume application.
OHP
12
3
Label permits low-volume application.
Bayer
12
3
Valent
24
3
carbamate
insect growth regu-A. azadirachtin
lator
(Azatin XL)
B. diflubenzuron
(Adept 25WP)
C. novaluron
(Pedestal)
pyrethroid
B. acephate
(PT 1300 Orthene TR)
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
C. cyfluthrin
(Decathlon 20WP)
D. deltamethrin*
(DeltaGard)
E. fenpropathrin*
(Tame 2.4EC Spray)
An aerosol.
Must contact insect. Repeat applications
as necessary. Label permits low-volume
application.
Use no more than twice per year and do
not exceed 52 oz/acre/year. Do not use on
poinsettia.
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse only labeled for greenhouse
use on anthurium, cacti, carnation, rose,
orchids, some foliage plants, young poinsettia, and some varieties of chrysanthemum. Can stunt new growth in roses.
An aerosol only for greenhouse use.
Label permits low-volume application.
Continued on next page . . .
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Treatment, continued
Class
pyrethroid
spinosyn
Pesticide
(trade name)
F. fluvalinate
(Mavrik Aquaflow)
G. permethrin
(Astro)
A. spinosad
(Conserve SC)
Manufacturer
Wellmark
REI1
12
FMC
12
Dow Agro
Sciences
4
Mode of
action2 Comments
3
Label permits low-volume application. Also
labeled as a cutting dip at 5 fl oz/100 gal.
3
Direct application to blooms may cause
browning of petals. Marginal leaf burn may
occur on salvia, dieffenbachia, and pteris
fern. Label permits low-volume application.
Do not apply more than 2 lb a.i./acre/year.
5
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus
persimilis.
1
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
2
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://irac-online.org/.
3
PBO = piperonyl butoxide
#
Acceptable for use on organically grown ornamentals.
*
Restricted use material. Permit required for purchase or use.
Important Links
• Degree-day model for Beet Armyworm in Floriculture
• Video presentation Using degree-days to time insecticide applications
Major Insect and Mite Pests
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BULB MITES (3/09)
Rhizoglyphus spp.
DESCRIPTION OF THE PEST
Bulb mites are white with large amber spots, brown legs, and are 0.55 to 0.75 mm long when fully grown.
They are slow moving and oval shaped, so are sometimes mistaken for insect eggs. These mites can be
found in hollowed out and decomposing portions of bulbs.
DAMAGE
Bulb mites enter the bulb and feed in protected cavities, where fungi and bacteria may cause extensive
decomposition of the bulb. They are associated with the spread of Fusarium, Stromatinia, and Pseudomonas
diseases of bulbs. Species of bulbs attacked include freesia, hyacinth, lilies, narcissus, and onions, as well
as underground peony rhizomes. Freesias are particularly affected because they require high temperature
storage to break dormancy, which allows rapid growth of bulb mite populations. Lilies are attacked below ground, which stunts growth. Feeding at ground level causes the plants to topple.
MANAGEMENT
Biological Control
Biological control has not been investigated.
Cultural Control
Bulbs may be disinfested by holding them for 24 hours at 100% relative humidity at 105.5°F. CO2 fumigation may be useful.
TREATMENT
Thoroughly clean bulbs, dip them in a sulfur fungicide solution, and dry them following harvest. The sulfur will control bulb mites as well as fungal diseases if the bulbs are being held at high temperatures.
However, high rates of sulfur may be phytotoxic. Abamectin (Avid), dicofol (Kelthane), some pyrethroids, and pyridaben (Sanmite) are possibly effective, but have not been evaluated.
Major Insect and Mite Pests
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CABBAGE LOOPER (5/10)
Trichoplusia ni
DESCRIPTION OF THE PEST
Loopers arch their backs as they crawl. Cabbage loopers are light green and usually have a narrow, white
stripe along each side and several narrow lines down the back. The dome-shaped eggs are laid singly on
the undersurfaces of older leaves. Adult moths have brown, mottled forewings marked in the center with
a small, silver figure 8.
DAMAGE
Young cabbage looper larvae feed primarily on the underside of lower leaves, skeletonizing them. Larger
cabbage loopers chew entirely through leaves and flowers.
MANAGEMENT
Biological Control
A number of parasites, both tachinid flies and parasitic wasps, attack Lepidoptera larvae and reduce their
population growth rate. However, most of these larvae continue feeding through to the last instar, so parasitized larvae will still damage crops. Viruses also do not usually kill the larvae until later instars.
Trichogramma spp. are commercially available egg parasites that can be effective against cabbage looper.
Applying insecticides other than Bacillus thuringiensis (Bt) products are likely to exclude parasites because
their residue are lethal to these beneficial insects. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because these pests feed on a large variety of plant species, keep production areas free of weeds (e.g.,
mustards) that serve as hosts to cabbage loopers. Exclusion of winged adults can be accomplished by covering openings to the greenhouses with screens. Screens are especially important when lights are used at
night in greenhouses to control flowering because lights attract adult moths. Individual seedling flats
may also be covered with screens to exclude adults and larvae. Row covers can be a practical measure to
exclude moths in field production as long as the mesh prevents entry of adults and the row cover is held
above the plant surface to eliminate oviposition through the fabric.
Monitoring and Treatment Decisions
If Bt sprays are planned, use pheromone traps to determine adult flight activity and mating. Once adults
are caught in traps, it is very likely that larvae are present and Bt should be applied as soon as possible
because it is most effective against young larvae. Use regular visual inspections of plants to detect larvae
and their damage. For guidelines on when to treat, see ESTABLISHING ACTION THRESHOLDS.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
botanical
Pesticide
(trade name)
A. pyrethrin+PBO3
(PT Pyrethrum TR)
carbamate
A. carbaryl*
(various)
insect growth regulator A. azadirachtin
(Azatin XL)
B. diflubenzuron
(Adept 25WP)
Manufacturer
REI1
Mode of
action2 Comments
Whitmire MicroGen
12
3/—
Bayer
12
1A
OHP
4
un
Chemtura
12
15
An aerosol.
Must contact insect. Repeat applications
as necessary. Label permits low-volume
application.
Continued on next page . . .
Major Insect and Mite Pests
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Treatment, continued
Pesticide
Class
(trade name)
insect growth regula- C. novaluron
tor, cont.
(Pedestal)
microbial
organophosphate
pyrethroid
spinosyn
1
2
3
#
*
Manufacturer
Chemtura
REI1
12
Mode of
action2 Comments
15
Use no more than twice per year and
don't exceed 52 oz/acre/year. Don't use
on poinsettia.
18
D. tebufenozide
Dow Agro
(Mimic, Confirm)
Sciences
A. Bacillus thuringiensis Valent
ssp. kurstaki#
(various products)
4
4
11
Most effective against early instar larvae;
pheromone trapping recommended for
timing applications.
A. acephate
(Orthene T, T&O
Spray)
Valent
24
1B
B. acephate
(PT 1300 Orthene TR)
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
C. cyfluthrin
(Decathlon 20WP)
D. deltamethrin*
(DeltaGard)
E. fenpropathrin*
(Tame 2.4EC Spray)
F. fluvalinate
(Mavrik Aquaflow)
Whitmire MicroGen
24
1B
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse only labeled for greenhouse
use on anthurium, cacti, carnation, rose,
orchids, some foliage plants, young poinsettia, and some varieties of chrysanthemum. Can stunt new growth in roses.
An aerosol only for greenhouse use.
Whitmire MicroGen
12
3
Check label. A fogger for greenhouse use
only.
FMC
12
3
Label permits low-volume application.
OHP
12
3
Label permits low-volume application.
Bayer
12
3
Valent
24
3
Label permits low-volume application.
Wellmark
12
3
G. permethrin
(Astro)
FMC
12
3
A. spinosad
(Conserve SC)
Dow Agro
Sciences
4
5
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia, and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus
persimilis.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://irac-online.org/.
PBO = piperonyl butoxide
Acceptable for use on organically grown ornamentals.
Restricted use material. Permit required for purchase or use.
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
DIAMONDBACK MOTH (5/10)
Plutella xylostella
DESCRIPTION OF THE PEST
When at rest, the adult diamondback male moth's wings meet over its back to show three yellow diamonds. The female moths are about 0.4 inch long and lay minute eggs singly or in groups of two or three
on the undersides of leaves. Each female lays an average of 75 eggs. First instar larvae mine leaves, then
are external leaf feeders for the remaining three instars. Mature larvae are about 0.4 inch long, are pale
green and wriggle actively when disturbed. An openly woven silk cocoon holds the pupa in place under
leaves. Development from egg to adult is 29, 16, and 12 days at temperatures of 68°, 77°, and 87°F, with
the greatest survival at 77°F.
DAMAGE
Diamondback moth larvae chew small circular holes in leaves from the undersides, giving the leaves a
shot-hole appearance. Very high populations can defoliate plants. Affected flowers include sweet alyssum, stock, candytuft, wallflower, and other plants in the cruciferous family.
MANAGEMENT
Biological Control
A number of parasites, both tachinid flies and parasitic wasps, attack Lepidoptera larvae and reduce their
population growth rate. However, most of these larvae continue feeding through to the last instar, so parasitized larvae will still damage crops. Viruses also do not usually kill the larvae until later instars. The
parasitic stingless wasps Cotesia plutellae, Diadegma insulare, and Microplitis plutellae are commercially
available for control of diamondback moth. Applying insecticides other than Bacillus thuringiensis (Bt)
products are likely to exclude parasites because the residues are lethal to these beneficial insects. For
more information, see BIOLOGICAL CONTROL.
Cultural Control
Because these pests feed on a large variety of plant species, keep production areas free of weeds (e.g.,
mustards) that serve as hosts to diamondback moths. Exclusion of winged adults can be accomplished by
covering openings to greenhouses with screens. Screens are especially important when lights are used at
night in greenhouses to control flowering because lights attract adult moths. Individual seedling flats
may also be covered with screens to exclude adults and larvae. Row covers can be a practical measure to
exclude moths in field production as long as the mesh prevents entry of adults and the row cover is held
above the plant surface to eliminate oviposition through the fabric. Also, intermittent overhead irrigation
can disrupt oviposition by diamondback moth.
Monitoring and Treatment Decisions
If Bt sprays are planned, use pheromone traps to determine adult flight activity and mating. Once adults
are caught in traps, it is very likely that larvae are present and Bt should be applied as soon as possible
because it is most effective against young larvae. Use regular visual inspections of plants to detect larvae
and their damage. Diamondback moth is resistant to many insecticides. For guidelines on when to treat,
see ESTABLISHING ACTION THRESHOLDS.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
botanical
carbamate
Pesticide
(trade name)
A. pyrethrin+PBO3
(PT Pyrethrum TR)
A. carbaryl*
(various)
Manufacturer
Whitmire MicroGen
Bayer
REI1
Mode of
action2 Comments
12
3/—
12
1A
An aerosol.
Continued on next page . . .
Major Insect and Mite Pests
Diamondback Moth (5/10)
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Treatment, continued
Pesticide
Class
(trade name)
insect growth regula- A. azadirachtin
tor
(Azatin XL)
microbial
organophosphate
pyrethroid
spinosyn
1
2
3
*
#
Manufacturer
OHP
REI1
4
Mode of
action2 Comments
un
Must contact insect. Repeat applications
as necessary. Label permits low-volume
application.
15
May damage poinsettias if used over labeled rate.
11
Most effective against early instar larvae;
pheromone trapping recommended for
timing applications.
B. diflubenzuron
Chemtura
(Adept 25WP)
A. Bacillus thuringiensis Valent
ssp. kurstaki#
(various products)
12
A. acephate
(Orthene T, T&O
Spray)
24
1B
B. acephate
Whitmire Micro(PT 1300 Orthene TR) Gen
A. bifenthrin
Whitmire Micro(Attain TR)
Gen
B. bifenthrin*
FMC
(Talstar Professional)
C. cyfluthrin
OHP
(Decathlon 20WP)
D. deltamethrin*
Bayer
(DeltaGard)
E. fenpropathrin*
Valent
(Tame 2.4EC Spray)
F. fluvalinate
Wellmark
(Mavrik Aquaflow)
24
1B
12
3
12
3
Check label. A fogger for greenhouse use
only.
Label permits low-volume application.
12
3
Label permits low-volume application.
12
3
24
3
Label permits low-volume application.
12
3
G. permethrin
(Astro)
FMC
12
3
A. spinosad
(Conserve SC)
Dow Agro
Sciences
4
5
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia, and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus
persimilis.
Valent
4
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse, only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia,
and some varieties of chrysanthemum.
Can stunt new growth in roses.
An aerosol only for greenhouse use.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://irac-online.org/.
PBO = piperonyl butoxide
Restricted use material. Permit required for purchase or use.
Acceptable for use on organically grown ornamentals.
Major Insect and Mite Pests
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FOLLIAR-FEEDING MEALYBUGS (5/10)
Citrus mealybug: Planococcus citri
Longtailed mealybug: Pseudococcus longispinus
Madeira mealybug: Phenacoccus madeirensis
DESCRIPTION OF THE PESTS
Mealybugs are slow-moving sucking insects that have a loose, waxy coating on the body, which gives
them their "mealy" appearance. The citrus mealybug is heavily and evenly covered with white, powdery
wax, except for a faint narrow streak down the middle. It has short, wax filaments along the sides and
hind filaments that are about one-fourth as long as the body. Both the citrus mealybug and the Mexican
mealybug lay eggs in ovisacs (eggs are within masses of cottony wax). The Mexican mealybug can be distinguished from the citrus mealybug by four rows of thinly waxed depressions down the back. The longtailed mealybug has four long terminal wax filaments, which it holds parallel to the axis of the body; it
also gives birth to live young. Mealybug infestations often occur underneath foliage and in hidden areas
within dense foliage.
DAMAGE
Mealybugs remove sap from plants, which can cause yellowing of leaves and decline in vigor. Mealybug
ovisacs and excreted honeydew are unsightly. Honeydew supports the growth of black sooty mold fungi
and attracts ants; ants may then carry mealybugs to uninfested plants and tend them for honeydew, as
well as protect them from natural enemies.
MANAGEMENT
Biological Control
Cryptolaemus montrouzieri, the mealybug destroyer lady beetle, is an effective predator of many mealybugs and other ovisac-forming sucking insects (such as green shield scale). Larval mealybug destroyers
themselves look like large, faster-moving mealybugs, but are readily distinguished by their chewing
mouthparts. Leptomastix dactylopii, a parasite of citrus mealybugs, is also commercially available. Effective
predators or parasites of longtailed mealybugs are not yet commercially available. For more information,
see BIOLOGICAL CONTROL.
Monitoring and Treatment Decisions
Carefully inspect plants being brought in to start a new crop to ensure that they are free of mealybugs
and other pests. If necessary, treat infested plants.
Regularly inspect plants for signs of honeydew (i.e., glistening, sticky leaves) and ant activity. Well-established infestations containing females with ovisacs are much more difficult to control with either systemic
or contact insecticides than new infestations because reproducing adults usually stop feeding and the females' bodies or the wax secretions help protect eggs or crawlers.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
biological
Pesticide
(trade name)
A. Beauveria bassiana#
(BotaniGard 22 WP)
(BotaniGard ES)
A. pyrethrin/PBO3
(PT Pyrethrum TR)
insect growth regula- A. azadirachtin
tor
(Azatin XL)
botanical
Major Insect and Mite Pests
Manufacturer
Laverlam
REI1
4
Whitmire
MicroGen
OHP
12
Mode of
action2 Comments
—
Treat every 7 days while insects are active. Do not tank mix with most fungicides
and wait 48 hours after application to apply a fungicide.
3/—
An aerosol.
4
un
Must contact insect. Repeat applications
as necessary. Only effective on
Foliar-Feeding Mealybugs (5/10)
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neonicotinoid
B. azadirachtin
(Ornazin 3%EC)
C. s-kinoprene
(Enstar II)
A. acetamiprid
(TriStar) 70WSP
B. dinotefuran
(Safari) 20G
C. imidacloprid
(Marathon 1G)
(Marathon II)
SePRO
12
un
Wellmark
4
7A
Cleary
12
4A
Valent
12
4A
Can be applied as a drench or foliar
spray.
OHP
12
4A
Syngenta
12
4A
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above. Apply only as a drench.
Can be applied as a drench or foliar
spray.
OHP
4
un
Do not spray plants under stress. Target
pest must be completely covered with
spray. Check label for list of plants that
can be treated. May cause injury to flowers.
Whitmire
MicroGen
Brandt
JMS Farms
12
—
4
4
—
—
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
A. acephate
(Acephate 97UP)
B. acephate
(Orthene T, T&O
Spray)
United
Phosphorus
Valent
24
1B
24
1B
C. acephate
(PT 1300 Orthene TR)
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
C. cyfluthrin
(Decathlon 20 WP)
D. deltamethrin*
(DeltaGard)
E. fenpropathrin*
(Tame 2.4 EC Spray)
F. fluvalinate
(Mavrik Aquaflow)
Whitmire Micro- 24
Gen
Whitmire Micro- 12
Gen
FMC
12
1B
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse, only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia and
some varieties of chrysanthemum. Can
stunt new growth in roses.
An aerosol for greenhouse use only.
3
A fogger for greenhouse use only.
3
Label permits low-volume application.
OHP
12
3
Label permits low-volume application.
Bayer
12
3
Valent
24
3
Label permits low-volume application.
Wellmark
12
3
G. permethrin
(Astro)
FMC
12
3
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia and
pteris fern. Label permits low-volume
(Marathon 60 WP)
D. thiamethoxam
(Flagship) 25WG
oil4
A. clarified hydrophobic
extract of neem oil#
(Triact 70)
B. horticultural oil5
(Ultra-Fine Oil)
(SafTSide)
(JMS Stylet Oil)
organophosphate
pyrethroid
immatures. Label permits low-volume application.
Do not exceed 22.5 oz/acre/application.
Major Insect and Mite Pests
Apply prebloom. Only effective on immatures. Also labeled for low volume use.
Apply as a foliar spray.
Foliar-Feeding Mealybugs (5/10)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
application. Do not apply more than 2 lb
a.i./acre/year.
1
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
2
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional
information, see their Web site at http://www.irac-online.org/.
3
PBO = piperonyl butoxide.
4
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
5
Check with certifier to determine which products are organically acceptable.
* Restricted use pesticide. Permit required for purchase or use.
#
Acceptable for use on organically grown ornamentals.
Major Insect and Mite Pests
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
FUNGUS GNATS (3/09)
Fungus Gnats: Bradysia coprophila, Bradysia impatiens
DESCRIPTION OF THE PESTS
Fungus gnats are small (2–5 mm long) mosquitolike flies with dark wings, delicate legs, and long antennae. They lay their eggs in soil, and the eggs hatch about 4 days later. There are four larval instars that
increase in size up to about 0.33 inch (8 mm). Larvae are clear, with visible internal organs, and have
shiny black head capsules. Initially larvae feed on root hairs and algae; later, larvae may feed on the insides of roots. When populations are high, larvae may bore into larger roots or stems that are in the soil.
Larvae will also feed on leaves touching the soil. One generation may complete development in 21 (72°F)
to 40 (61°F) days.
DAMAGE
Larvae usually feed on roots and algae within 1 inch of the soil surface. Root feeding by larvae can allow
entry of plant pathogens. Direct damage through root feeding can cause wilting even though the plants
are being sufficiently watered. Damage is particularly severe in propagation areas, in seedling flats, and
with especially sensitive crops. Adult fungus gnats also disseminate soil-inhabiting pathogens on their
bodies and in their feces. Fungus gnat adults can be a nuisance when present in large numbers.
MANAGEMENT
Biological Control
Biological control agents include nematodes (Steinernema feltiae), soil-inhabiting predaceous mites (Hypoaspis miles), and the bacteria Bacillus thuringiensis (Gnatrol). For more information, see BIOLOGICAL
CONTROL.
Cultural Control
Keep production areas free of weeds and algal scum, which can serve as breeding sites for fungus gnat
populations. Maintaining overwatered conditions and using either incompletely composted organic matter or manure in potting media provides ideal conditions for fungus gnats. Commercial sources of peat
may be infested with fungus gnats and should be steamed before use when growing crops sensitive to
fungus gnats.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture adult fungus gnats. For more information, see
MONITORING WITH STICKY TRAPS. Small emergence traps can also be used to determine precisely
where adults are emerging. Larval populations can be monitored with cubes or slices of potatoes pressed
just into the soil. Fungus gnat larvae can be readily seen feeding on the potato pieces. For more information on treatment decisions, see ESTABLISHING ACTIONTHRESHOLDS.
Apply insecticide drenches to the top 1 inch of soil to kill larvae; avoid applying excessive spray volume
that may leach or move insecticide too deeply into growing media. Pyrethrins and other adulticides such
as aerosols, foggers, or sprays can quickly, but temporarily, reduce adult fungus gnat numbers.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
biological
botanical
Pesticide
(trade name)
Bacillus thuringiensis
ssp. israelensis#
A. (Gnatrol)
pyrethrin/PBO3
A. (PT Pyrethrum TR)
Major Insect and Mite Pests
Manufacturer
REI1
Valent
Whitmire
MicroGen
4
12
Mode of
action2 Comments
Do not apply with fertilizers or fungicides
containing copper or chlorine. Not effec11
tive on shore flies.
An aerosol. Also effective against adults.
3/—
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azadirachtin
(Azatin XL)
insect growth regulator
A.
azadirachtin
B. (Ornazin 3%EC)
4
un
SePRO
12
un
Syngenta
12
17
Do not exceed 22.5 oz/acre/application
Certification training required to use this
product. Also effective against shore fly
larvae.
Chemtura
12
15
Apply as spray or drench to top 2 inches
of soil.
pyriproxyfen
E. (Distance)
Valent
12
7C
Do not apply more than 2 times per cropping cycle or per 6 months.
s-kinoprene
F. (Enstar II)
Wellmark
4
7A
Apply prebloom. Also labeled for low volume use.
Cleary
12
4A
Valent
12
4A
OHP
12
4A
Syngenta
12
United Phosphorus
24
4A
cyromazine
C. (Citation 75 WP)
diflubenzuron
D. (Adept 25WP)
neonicotinoid
organophosphate
pyrethroid
Must contact insect. Repeat applications
as necessary. Only effective on larvae.
Label permits low-volume application.
OHP
acetamiprid
A. (TriStar) 70WSP
dinotefuran
B. (Safari) 20G
imidacloprid
(Marathon 1G)
C. (Marathon II)
(Marathon 60 WP)
thiamethoxam
D. (Flagship) 25WG
acephate
A. (Acephate 97UP)
Apply as a foliar spray.
acephate
(Orthene T,
B. T&O Spray)
Valent
acephate
Whitmire MicroC. (PT 1300 Orthene TR) Gen
bifenthrin
Whitmire MicroA. (Attain TR)
Gen
bifenthrin*
B. (Talstar Professional) FMC
cyfluthrin
C. (Decathlon 20 WP)
OHP
D. deltamethrin*
(DeltaGard)
Bayer
fenpropathrin*
E. (Tame 2.4 EC Spray)
Valent
1B
24
1B
24
1B
12
3
12
3
12
3
12
3
24
3
fluvalinate
F. (Mavrik Aquaflow)
Wellmark
12
3
permethrin
G. (Astro)
FMC
12
3
Major Insect and Mite Pests
Can be applied as a drench or foliar
spray.
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above. Apply only as a drench.
Can be applied as a drench or foliar
spray.
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouses only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia,
and some varieties of chrysanthemum.
Can stunt new growth in roses.
An aerosol for greenhouse use only.
Check label. A fogger for greenhouse use
only.
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application. Also labeled
as a cutting dip at 5 fl oz/100 gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia, and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
1
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
2
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional
information, see their Web site at http://www.irac-online.org/.
3
PBO = piperonyl butoxide
* Restricted use pesticide. Permit required for purchase or use.
#
Acceptable for use on organically grown ornamentals.
Major Insect and Mite Pests
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
LEAFHOPPERS AND SHARPSHOOTERS (5/10)
Aster leafhopper: Macrosteles quadrilineatus (=M. fascifrons)
Blue-green sharpshooter: Graphocephala atropunctata
Glassy-winged sharpshooter: Homalodisca vitripennis (=H. coagulata)
Two-spotted leafhopper: Sophonia rufofascia
DESCRIPTION OF THE PESTS
Leafhoppers, including a subgroup called sharpshooters, are in the family Cicadellidae. All have mouthparts that allow them to pierce the plant tissue and feed on plant juices. Most leafhoppers are about 0.25
inch long and slender. Species may be brightly colored or similar in color to the host plant. They often
jump away or move sideways when disturbed. Pale cast skins may be found on leaf surfaces. Leafhoppers have incomplete metamorphosis. Immatures (nymphs) are similar in structure to adults, but are
smaller, wingless, and may differ in color.
Glassy-winged sharpshooter
Adult glassy-winged sharpshooters are about 0.5 inches long and dark brown in color. Wings are membranous and translucent, with reddish veins. The insects overwinter as adults and begin to lay egg
masses about late February. There appear to be two generations of glassy-winged sharpshooters per year
in California. Eggs are laid under the surface of the leaf epidermis. The gray-colored nymphs are smaller
than the adults and wingless. There are 5 immature stages. As they feed on xylem tissue, they excrete a
large amount of liquid substance that drops to the leaves or the ground below. The glassy-winged sharpshooter has a broad host range that includes many ornamental plant species.
Aster leafhopper
The aster leafhopper is also called the six-spotted leafhopper because it has three pairs of black spots on
its head. The adults are small (about 0.12 inch long) and usually light green to yellow, with black marking
on the thorax and abdomen. Their wings are transparent. Nymphs are usually dark green.
Blue-green sharpshooter
The blue-green sharpshooter has green to bright blue wings, head, and thorax, and yellow legs and abdomen, which are visible on the underside. It is about 0.4 inches long. There is one generation a year in most
of California and a second generation in some southern areas of the state. Adults become active in late
winter to early spring. They can become abundant in ornamental landscaping around homes. They also
feed on numerous weeds mostly along stream banks or in ravines or canyons where there is dense vegetative growth. As natural vegetation dries up, adults disperse into crops and irrigated plantings. Eggs
hatch from May through July with some of the nymphs becoming adults by mid-June.
Two-spotted leafhopper
Adults are about 0.25 inches long and pale yellow with a dark stripe down the center of the back. On the
end of the wings are two prominent eye spots that make it appear that the leafhopper is walking backwards. This leafhopper feeds on a wide range of ornamental plants. Feeding may cause chlorosis of
leaves in some species.
DAMAGE
Leafhoppers are pests primarily because some are vectors of plant pathogens. The glassy-winged sharpshooter and the blue-green sharpshooter transmit a bacterial pathogen Xylella fastidiosa that grows in the
xylem, or water-conducting tissue, of certain plant species. Xylella fastidiosa can cause a number of plant
diseases in a variety of hosts. Thus far, strains of X. fastidiosa that cause oleander leaf scorch, Pierce's disease of grapevines, almond leaf scorch, and alfalfa dwarf have been identified in California. The strains of
the pathogen that infect oleander do not appear to infect grape and are genetically distinct from the other
strains. The aster leafhopper is one of several leafhoppers that can transmit the phytoplasma pathogens
that cause aster yellows disease in many plant hosts.
In addition to the transmission of pathogens, leafhopper feeding can cause leaves to appear stippled,
pale, or brown, and shoots may curl and die. Excrement exuded during feeding can serve as a substrate
for the growth of sooty mold, or discolor leaves with a white chalky film.
Glassy-winged sharpshooter is under quarantine in California and shipment from infested to noninfested
areas requires specific treatments.
Major Insect and Mite Pests
Leafhoppers and Sharpshooters (5/10)
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
MANAGEMENT
Management of leafhoppers and sharpshooters in nursery crops is focused primarily on exclusion techniques. Plants can be protected from these pests and the transmission of pathogens with the use of row
covers and screening; reflective mulches may also be useful. Good weed management is important in areas surrounding nurseries to prevent the buildup of populations and migration into the nursery when the
surrounding vegetation dries. In nurseries that have had past problems with glassy-winged sharpshooters, a quarantine pest, preventive insecticide treatments are advisable. Otherwise, monitor these pests to
detect an influx of populations into the nursery.
Biological Control
There are no commercial sources of biological control agents for leafhoppers currently available; however, there is a fairly high level of naturally occurring egg parasitism of glassy-winged sharpshooters late
in the season. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Leafhoppers can be excluded from growing areas using screening or row covers. Identify potential
sources of pathogens that are near growing areas. Remove weeds to eliminate sources of leafhoppers or
pathogens near growing areas. If such sources cannot be removed, avoid planting crops susceptible to
disease near these alternate hosts.
For open field flower or nursery production, silver reflective plastic mulches may be of value. Reflective
mulches have been shown to repel leafhoppers in another crop (corn), thus reducing pest numbers in and
around the plant canopies. In addition, Xylella transmission by the leafhopper vectors was greatly reduced, thus reducing corn stunt disease incidence. For best results, apply reflective mulches at the time of
planting or transplanting the crop. Apart from reducing leafhopper and pathogen incidence, silver reflective mulch may increase cut-flower production and reduce the crop requirement for irrigation, water and
fertilizer. Row covers, screening, and mulching are acceptable practices for organic production.
Monitoring and Treatment Decisions
Leafhoppers are dormant through the winter months and will require little attention. Activity and egg
laying begin in early spring. Begin monitoring in February to March and continue through September.
For nurseries with chronic glassy-winged sharpshooter problems, apply preventive treatments when
adults are first detected. Otherwise, monitor nursery borders to detect the influx of leafhopper/sharpshooters and treat if necessary.
Place yellow sticky traps around the nursery border and throughout the nursery at canopy height (4
cards per acre) to detect migration of sharpshooters and leafhoppers into the nursery. Check cards at least
once a week for adult sharpshooters. Treat if any adult glassy-winged sharpshooters are detected in the
traps. If glassy-winged sharpshooters are not present but five to ten leafhoppers or other sharpshooters
are being caught in sticky traps, a treatment may be necessary to stem the influx of these other species. A
major management consideration is that economic damage caused by the leafhopper should equal or exceed the cost of any necessary management. For more information, see MONITORING WITH STICKY
TRAPS.
Other monitoring methods, including beating samples and visual counts, can be used to detect the presence of leafhoppers and sharpshooters. Beat or sweep sampling for nymphs and adults is most effective
when temperatures are cool (less than 60°F). At warmer temperatures the insects will fly away before
they can be counted. To conduct a beat sample, place a 2-foot square sheet of white material underneath
the canopy to be sampled. Strike the canopy with a stick or shake it vigorously to dislodge insects, and
count the number on the sheet. A sweep net may be also used to sample foliage for the presence of adults
and nymphs. Visual inspection of leaves, stems, and branches is perhaps the best method for detecting all
stages. Insects may try to move to the far side of the stem to avoid detection. Placing a hand close behind
the stem being observed will make the insects move to the front where they can be seen. (Glassy-winged
sharpshooter egg masses can be easily detected by inspecting the undersides of leaves against a sunny
sky.)
For information on making treatment decisions, see ESTABLISHING ACTION THRESHOLDS.
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Quarantine Requirements. Nurseries are considered infested if 5 or more glassy-winged sharpshooters
are collected on sticky cards that are within a 300-yard radius of each other (not less than one card per
half acre). Shipment of nursery stock from glassy-winged sharpshooter-infested areas to noninfested areas within and outside of California requires additional treatments. Contact your county Agricultural
Commissioner's office for more information.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
Pesticide
(trade name)
Manufacturer REI1
Mode of
action2 Comments
botanical
pyrethrin/PBO3
A. (PT Pyrethrum TR)
Whitmire MicroGen
12
3/—
An aerosol.
carbamate
carbaryl*
A. (Sevin SL)
Bayer
12
1A
May be applied through sprinkler irrigation systems only.
Must contact insect. Repeat applications
as necessary. Aphid suppression only.
Label permits low-volume application.
insect growth regulaazadirachtin
tor
A. (Azatin XL)
azadirachtin
B. (Ornazin 3%EC)
s-kinoprene
C. (Enstar II)
neonicotinoid
oil4
organophosphate
acetamiprid
A. (TriStar 70WSP)
OHP
4
un
SePRO
12
un
Wellmark
4
7A
Cleary
12
4A
Do not exceed 22.5 oz/acre/application.
Apply prebloom. Also labeled for low volume use.
imidacloprid
(Marathon 1G)
B. (Marathon II)
OHP
12
4A
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
imidacloprid
C. (Marathon 60 WP)
OHP
12
4A
As above, but apply only as a drench.
Do not spray plants under stress. Target
pest must be completely covered with
spray—this material may not effectively
control melon aphid because it is often on
the underside of lower leaves. Check label for list of plants that can be treated.
May cause injury to flowers.
clarified hydrophobic
extract of neem oil#
A. (Triact 70)
horticultural oil5
(Ultra-Fine Oil)
(SafTSide)
B. (JMS Stylet Oil)
acephate
A. (Acephate 97UP)
OHP
4
un
Whitmire
MicroGen
Brandt
JMS Farms
United
Phosphorus
12
—
4
4
—
—
24
1B
acephate
(Orthene T, T&O
B. Spray)
Valent
acephate
Whitmire
C. (PT 1300 Orthene TR) MicroGen
Major Insect and Mite Pests
24
1B
24
1B
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. Only
labeled for use on anthurium, cacti, carnation, rose, orchids, some foliage plants,
young poinsettia and some varieties of
chrysanthemum. Can stunt new growth in
roses.
An aerosol that is only for greenhouse
use.
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pyrethroid
soap4
1
2
3
4
5
*
#
bifenthrin*
A. (Talstar Professional) FMC
cyfluthrin
B. (Decathlon 20 WP)
OHP
deltamethrin
C. (DeltaGard T&O)
Aventis
fenpropathrin*
D. (Tame 2.4 EC)
Valent
12
3
Label permits low-volume application.
12
3
Label permits low-volume application.
12
3
For outdoor use only.
24
3
Label permits low-volume application.
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
For greenhouse and nursery use. Apply
at 7-day intervals. Do not apply more
than 52.4 fl oz of concentrate/acre/year.
Do not mix with EC formulations or oils.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
Must contact insect, so thorough coverage is important. Repeat weekly as
needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or
newly rooted cuttings. Do not add adjuvants.
fluvalinate
E. (Mavrik Aquaflow)
Wellmark
12
3
lambda-cyhalothrin*
F. (Scimitar GC)
Syngenta
24
3
permethrin
G. (Astro)
FMC
12
3
potash soap#
A. (M-Pede)
Dow Agro
Sciences
12
—
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
PBO = piperonyl butoxide
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
Check with certifier to determine which products are organically acceptable.
Restricted use material. Permit required for purchase or use.
Acceptable for use on organically grown ornamentals.
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LEAFMINERS (5/10)
Pea leafminer: Liriomyza huidobrensis
Serpentine leafminer: Liriomyza trifolii
DESCRIPTION OF THE PESTS
Adult leafminers are small (1.8 mm), yellow and black flies that are about the same size and shape as fruit
flies. In contrast to shore flies, leafminer adults are brightly colored and have clear wings. They are often
found on yellow flowers or objects. Females insert their eggs within leaves and also puncture the leaf surface with the ovipositor to feed on damaged plant tissue. Larvae have three instars, forming larger mines
inside the leaves as they grow. Liriomyza trifolii mines are readily observed from the top of the leaf, while
Liriomyza huidobrensis mines may only be visible from the underside of the leaf. Liriomyza huidobrensis mines
tend to follow the veining pattern of the leaf. After completing their feeding, larvae drop from leaves to pupate in the soil. Liriomyza trifolii can complete one generation in 14 days at 95°F, 64 days at 59°F.
DAMAGE
When populations are high, stippling, caused by females puncturing the leaves with their ovipositor to
feed and lay eggs, can be serious. However, most of the damage is caused by the larval mines that detract
from the aesthetic value of the crop.
MANAGEMENT
Biological Control
Biological control normally keeps these species in check in outdoor situations. Outbreaks of leafminers
frequently occur following the disruption of their parasites with broad-spectrum insecticides. For this reason, try to use selective insecticides through the entire production cycle so that parasites can be conserved. The parasites Diglyphus spp. and Dacnusa sibirica are commercially available to control leafminers
and may be useful in greenhouse situations, especially if greenhouses are screened to exclude adult
leafminer movement into greenhouses. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because leafminers feed on a large variety of plant species, keep production areas free of weeds, which
can serve as reservoirs for leafminer populations. Leafminers breed in weed or crop hosts outside of
greenhouses, so weed management outside the greenhouse and exclusion of immigrating adults are especially valuable as management practices. Effective screens require a pore width of 600 microns or smaller.
Carefully inspect plants being brought in to start a new crop to ensure that they are free of mines; discard
infested plants or leaves. Steam planting beds immediately after removing infested plantings to eliminate
leafminer pupae in the soil.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture adults. Place one trap per 10,000 sq. feet and monitor weekly. For more information, see MONITORING WITH STICKY TRAPS and ESTABLISHING
ACTION THRESHOLDS.
Insecticide resistance is so widespread that the effectiveness of each material depends on the tolerance of
each treated population. Rotation to a new class of insecticides every 1 to 2 months is advised.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Pesticide
Class
(trade name)
insect growth regula- A. azadirachtin
(Azatin XL)
tor
B. azadirachtin
(Ornazin 3%EC)
Major Insect and Mite Pests
Manufacturer REI1
OHP
4
SePRO
12
Mode of
action2 Comments
un
Must contact insect. Repeat applications
as necessary. Label permits low-volume
application.
un
Do not exceed 22.5 oz/acre/application.
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C. cyromazine
(Citation 75 WP)
Syngenta
12
17
D. novaluron
(Pedestal)
Chemtura
12
15
E. pyriproxyfen
(Distance)
Valent
12
7C
macrocyclic lactone A. abamectin
(Avid 0.15EC)
Syngenta
12
6
Label permits low-volume application.
neonicotinoid
A. acetamiprid
(TriStar 70WSP)
Cleary
12
4A
Apply as a foliar spray.
B. dinotefuran
(Safari) 20G
C. imidacloprid
(Marathon 1G)
(Marathon II)
Valent
12
4A
OHP
12
4A
Syngenta
12
4A
Can be applied as a drench or foliar
spray.
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above. Apply only as a drench.
Can be applied as a drench or foliar
spray.
A. acephate
(Orthene T, T&O
Spray3)
Valent
24
1B
B. acephate
(PT 1300)
(Orthene TR)
A. permethrin
(Astro)
Whitmire
MicroGen
24
1B
FMC
12
3
pyrrole
A. chlorfenapyr
(Pylon)
OHP
12
13
spinosyn
A. spinosad
(Conserve SC)
Dow Agro
Sciences
4
5
(Marathon 60 WP)
D. thiamethoxam
(Flagship) 25WG
organophosphate
pyrethroid
1
2
3
*
Certification training required to use this
product. Also effective against fungus
gnat larvae. Labeled for low volume applications.
Use no more than twice per year and
don't exceed 52 oz/acre/year. Don't use
on poinsettia.
Do not apply more than 2 times per cropping cycle or per 6 months.
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia and
some varieties of chrysanthemum. Can
stunt new growth in roses.
An aerosol for greenhouse use only.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia, and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
Greenhouse use only. Do not exceed 3
applications/growing cycle.
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus
persimilis.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with
chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional
information, see their Web site at http://www.irac-online.org/.
This material is effective, but not specifically labeled for this pest.
Restricted use pesticide. Permit required for purchase or use.
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LEAFROLLERS (5/10)
Fruittree leafroller: Archips argyrospila
Light brown apple moth: Epiphyas postvittana
Obliquebanded leafroller: Choristoneura rosaceana
Omnivorous leafroller: Platynota stultana
DESCRIPTION OF THE PESTS
Fruittree leafroller and omnivorous leafroller are the primary leafrollers found in nursery stock, but
obliquebanded leafroller and orange tortrix can also be found. There are other leafrollers such as Amorbia
or western avocado leafroller, Amorbia cuneana, which attacks avocado primarily, and light brown apple
moth (Epiphyas postvittana), which has been detected in California but is not established in the state.
Fruittree leafrollers have one generation per year. Overwintering eggs hatch in spring, and larvae can be
found feeding on leaves until about June. The larvae are dark green caterpillars with black heads. Adult
moths appear in June or July and lay the overwintering eggs.
The fruittree leafroller overwinters in flat egg masses on scaffold limbs and twigs. Eggs hatch in spring
from March to as late as mid-May in cooler areas. Young larvae are dark green caterpillars with black
heads. As the larva matures, its head turns dark brown and the plate immediately behind the head becomes a tan to olive-green color. Larvae roll a leaf and web it together to form a protective shelter. At maturity the larvae are 0.75 to 1 inch long. When disturbed, they wiggle backwards and drop to the ground
on a silken thread. The pupa is just under 0.5 inch long, light to dark brown, and is usually formed within
the rolled leaf.
The adult moth has a wingspan of less than one inch. Like other leafrollers, its wings have a bell-shaped
outline when viewed from above. The forewings are mottled shades of brown and tan with gold-colored
flecks, while the hind wings are whitish to gray.
Omnivorous leafrollers generally overwinter as adults, emerging in March. Caterpillars may differ in body
color from cream to brown with light brown to black head capsules and resemble other tortricid species,
except that they have white, slightly convex and oval tubercles at the base of each bristle on the upper
side of the abdomen. Mature larvae are about 0.6 inch (1.5 cm) long and are green to cream colored but so
translucent that you can see the main blood vessel running down their backs.
Adults are small, dark brown moths, 0.375 to 0.5 inch long with a dark band on the wing and a long
snout. Female moths lay overlapping eggs in clusters that resemble fish scales on the upper surface of
leaves. Often eggs are laid on weed hosts such as horseweed, common lambsquarters, little mallow, curly
dock, and legumes. Omnivorous leafroller has four to six generations per year depending on climatic conditions.
Obliquebanded leafroller may be the most common leafroller found in the Sacramento Valley. It has two
generations per year in the Sacramento Valley. Larvae are yellowish green caterpillars with brown to
black heads. The obliquebanded leafroller appears about the same time in spring as the fruittree leafroller
and resembles the fruittree leafroller as a larva. The obliquebanded leafroller, however, has multiple generations each year and is present throughout the summer.
Adults (moths) of obliquebanded leafrollers are reddish brown and have alternating light and dark
brown bands across their forewings. Obliquebanded leafroller overwinters as larvae in the bud scales of
twigs. They begin emerging in mid-May in warmer districts to early June in cooler areas. There are two to
three generations each year.
Another leafrolling caterpillar, orange tortrix, occurs throughout the year. As a larva, it is about 0.5 inch
long when mature and varies in color from light green to tan. The activities of orange tortrix and obliquebanded leafrollers are similar to those of the fruittree leafroller, but unlike the fruittree leafroller, which
overwinters in the egg stage, these two species overwinter as larvae.
Light brown apple moth, an exotic pest native to Australia, has been detected in California but has not
been established here. Because it is a quarantine pest with special requirements regarding inspection and
treatment, consult the University of California's online publication (PDF) and the California Department
of Food and Agriculture (CDFA) website or a County Agricultural Commissioner. The light brown apple
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moth larvae cannot be reliably identified using morphological characters with our current knowledge.
Deliver suspect larvae (see field identification guide PDF) to CDFA, usually via a county agricultural
commissioner, for proper identification. The most efficient and reliable way of obtaining male adults is
with the use of light brown apple moth pheromone traps. There are many native tortricids that can be
confused with this pest. If you find a tortricid moth in a light brown apple moth pheromone trap, take it
to your county agricultural commissioner's office for positive identification.
DAMAGE
Leafrollers, which can feed on leaves and flower buds, are generally minor pests in ornamental nursery
crops but can be a serious defoliating pest when populations are high. In spring, small larvae spin webs
and feed on new foliage. They can attack a wide variety of trees including deciduous and live oaks, ash,
birch, California buckeye, box elder, elm, locust, maple, poplar, and willow. Roses can also be targets.
MANAGEMENT
Regular monitoring each season is important so that prompt action can be taken if damaging populations
develop. Throughout the year, watch for the presence of leafrollers while monitoring for other pests.
Biological Control
A number of general predators, such as lacewing larvae, assassin bugs, tachinid flies, and wasp parasites
attack leafroller larvae or eggs. These natural enemies help keep fruittree leafroller populations at low,
nondamaging levels, but occasional outbreaks occur. Preservation of natural enemy populations is an important part of keeping leafroller numbers low. Use selective materials that are least disruptive of biological control when treating these and other pests.
Monitoring
Inspect plants during the winter period for egg masses. Egg masses are about the size of a thumbprint
and laid on smooth wood. Also check blooms and leaves for the presence of the leafroller and other larvae. To monitor caterpillars, search the outer canopy. Begin checking once a week starting from the
spring leaf flush. Closely examine blossoms and vegetative shoots in the nursery in the spring for the
presence of caterpillars, webbed or rolled leaves, or feeding damage.
Decisions to treat the larval stage of the leafrollers should be based on the presence of caterpillars observed from periodic visual inspection of the plants.
Treatment Decisions
If damaging populations are observed, a number of environmentally friendly chemicals are effective in
controlling this pest, including Bacillus thuringiensis and spinosad (Entrust, Conserve).
Bacillus thuringiensis (Bt) is only effective on fruittree leafroller larvae when they are small (less than 0.5
inch long) and usually requires more than one application. Caterpillars must ingest the pesticide to be
killed.
Spinosad is a material that is effective on young larvae and is often preferred over Bt because it has a
longer residual and slightly more efficacious against older larvae.
The stomach poison cryolite is specific to foliage-feeding pests. These insecticides are relatively nontoxic
to parasites that attack the caterpillars and beneficial insects and mites that feed on other citrus pests.
Carbaryl (Sevin) can be effective against leafroller larvae.
Optimum control and a minimum amount of damage by fruittree leafrollers occur when a spray is applied at the time of larval hatching or shortly afterwards. To determine this time, inspect twigs showing
flushes of new foliage and look for feeding injury and the small caterpillars. If egg masses are found,
check them regularly for signs of larval exit holes. High-pressure spray is needed to force the material
into the leaf rolls and other protected areas where larvae are found.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
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Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
Pesticide
(trade name)
biological
A. Bacillus thuringiensis
ssp. kurstaki#
(various products)
carbamate
A. carbaryl*
(various)
insect growth regula- A. diflubenzuron
(Adept 25WP)
tor
mineral
spinosyn
1
2
A. cryolite
(ProKil Cryolite 96)
(Kryocide 96WP)
A. spinosad
(Conserve SC)
Manufacturer REI1
Mode of
action2 Comments
Valent
4
11
Bayer
12
1A
Chemtura
12
15
Gowan
Cerexagri
Dow Agro
Sciences
12
12
4
un
un
5
Most effective against early instar larvae;
pheromone trapping recommended for
timing applications.
Include vegetable oil at the rate of 1
qt/acre. Do not apply after petal fall. Do
not exceed 2 applications in any given
season. Allow 21 days between applications.
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus persimilis.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
# Acceptable for use on organically grown ornamentals.
*
Restricted use pesticide. Permit required for purchase or use.
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ROOT MEALYBUGS (5/10)
Rhizoecus spp.
DESCRIPTION OF THE PESTS
Root mealybugs are belowground dwelling mealybugs that feed on the roots of plants. These mealybugs
have a thin, uniform waxy coating and lack the terminal wax filaments typical of their foliar-feeding relatives.
DAMAGE
The only outward sign of root mealybug feeding may be a decline in the health of infested plants. When
plants are removed from the pot, the whitish mealybugs feeding on the roots are then observed.
MANAGEMENT
Biological Control
Biological control has not been investigated.
Cultural Control
Discard infected and surrounding plants. Control ants.
Monitoring and Treatment Decisions
Examine plant root balls when monitoring and when plants are declining. The presence of ants climbing
on the plant can also indicate a problem with mealybugs. Rogue and discard infected plants. Treat with a
soil drench or discard the surrounding plants.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
botanical
neonicotinoid
organophosphate
pyrethroid
Pesticide
(trade name)
pyrethrin/PBO3
A. (PT Pyrethrum TR)
imidacloprid
(Marathon 1G)
A. (Marathon II)
(Marathon 60 WP)
acephate
A. (Acephate 97UP)
Manufacturer
Whitmire
MicroGen
REI1
Mode of
action2 Comments
12
3/—
OHP
12
4A
United Phosphorus
24
1B
acephate
B. (Orthene T,T&O Spray) Valent
bifenthrin
A. (Talstar Professional) FMC
cyfluthrin
B. (Decathlon 20 WP)
OHP
fenpropathrin*
C. (Tame 2.4 EC Spray) Valent
Major Insect and Mite Pests
An aerosol.
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above, but apply only as a drench.
24
1B
A number of chrysanthemum varieties
have exhibit ed phytotoxic reactions. In
greenhouse, only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia and
some varieties of chrysanthemum. Can
stunt new growth in roses.
12
3
Label permits low-volume application.
12
3
Label permits low-volume application.
24
3
Label permits low-volume application.
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pyrethroid/
neonicotinoid
fluvalinate
D. (Mavrik Aquaflow)
Wellmark
12
3
permethrin
E. (Astro)
FMC
12
3
cyfluthrin/imidacloprid
A. (Discus)
OHP
12
3/4A
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
1
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
2
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with
chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional
information, see their Web site at http://www.irac-online.org/.
3
PBO = piperonyl butoxide.
* Restricted use material. Permit required for purchase or use.
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SHORE FLY (5/10)
Scatella stagnalis
DESCRIPTION OF THE PEST
This fly breeds in overwatered conditions in association with algae. The adult is small (2 mm) and dark.
The overall appearance is similar to a fruit fly; having short antennae and shorter legs than fungus gnats.
The pair of dark wings has three white spots on each wing. When the fly is at rest, there appear to be five
spots because the wings overlap.
Small, oblong eggs are laid in algal scum where larvae feed. Shore fly larvae have no distinct head capsule, and the body is opaque yellow, white, or brown. Both the dark brown pupa and the larva have a
forked air tube at the rear end.
DAMAGE
Large populations of shore flies can be a nuisance. Neither the adults nor larvae feed on plants. However,
adult shore flies have been implicated in the spread of fungal spores in greenhouses. Fecal spots on leaves
produced by resting adults can cause aesthetic damage to plants.
MANAGEMENT
Biological Control
Biological control of shore flies has not been investigated.
Cultural Control
Do not overwater. Control algae growing underneath benches, along irrigation lines, and in drainage areas.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture adult shore flies, see MONITORING WITH
STICKY TRAPS. Because these flies do not directly feed on plants, treatment may not be essential unless
there is a large nuisance population. Foggers and aerosols may be better at controlling adults than sprays.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
botanical
Manufacturer REI1
Mode of Comments
action2
Whitmire
MicroGen
12
3/—
An aerosol. Also effective against adults.
OHP
4
un
B. cyromazine
(Citation 75 WP)
Syngenta
12
17
C. diflubenzuron
(Adept 25WP)
Chemtura
12
15
Must contact insect. Repeat applications
as necessary. Only effective on larvae.
Label permits low-volume application.
Certification training required to use this
product. Also effective against shore fly
larvae.
Apply as spray or drench to top 2 inches
of soil.
D. pyriproxyfen
(Distance)
Valent
12
7C
Do not apply more than 2 times per cropping cycle or per 6 months.
E. s-kinoprene
(Enstar II)
A. imidacloprid
(Marathon 1G)
Wellmark
4
7A
OHP
12
4A
Apply prebloom. Also labeled for low volume use.
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
Pesticide
(trade name)
A. pyrethrin/PBO3
(PT Pyrethrum TR)
insect growth regula- A. azadirachtin
(Azatin XL)
tor
neonicotinoid
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bedding plants intended to be used as
food crops.
organophosphate
(Marathon 60 WP)
A. acephate
(Orthene T, T&O
Spray)
Valent
B. acephate
Whitmire
(PT 1300 Orthene TR) MicroGen
pyrethroid
1
2
3
*
As above. Apply only as a drench.
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouse only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia,
and some varieties of chrysanthemum.
Can stunt new growth in roses.
24
1B
24
1B
An aerosol for greenhouse use only.
A. bifenthrin
(Attain TR)
Whitmire Micro-12
Gen
3
Check label. A fogger for greenhouse use
only.
B. bifenthrin*
(Talstar Professional)
C. cyfluthrin
(Decathlon 20 WP)
D. fenpropathrin*
(Tame 2.4 EC Spray)
E. fluvalinate
(Mavrik Aquaflow)
FMC
12
3
OHP
12
3
Valent
24
3
Wellmark
12
3
F. permethrin
(Astro)
FMC
12
3
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application.
Also effective against adults. Label permits low-volume application. Also labeled
as a cutting dip at 5 fl oz/100 gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia, and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with
chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional
information, see their Web site at http://www.irac-online.org/.
PBO = piperonyl butoxide
Restricted use pesticide. Permit required for purchase or use.
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SNAILS AND SLUGS (3/21)
Amber snail: Novisuccinea spp., Succinea spp.
Brown garden snail: Cornu aspersum =Helix aspersa =Cantareus aspersus
Cellar glass-snail: Oxychilus cellarius
Garden slug: Arion hortensis
Gray garden slug: Deroceras reticulatum =Agriolimax reticulatus
Greenhouse slug: Milax gagates
Threebanded garden slug: Ambigolimax valentianus =Lehmannia valentiana
Tramp slug: Deroceras invadens
White garden snail: Theba pisana
DESCRIPTION OF THE PESTS
Snails and slugs are mollusks with similar anatomy and biology, except slugs lack an external shell. As
they feed and move, slugs and snails secrete mucus, which dries to form a silvery to whitish trail that
indicates these pests' presence. Note that fungus gnat larvae also leave silvery trails on growing media,
which when abundant can resemble trails of slugs and snails.
Snails and slugs are active mostly at night and on cool, cloudy, damp, and foggy days. On sunny days,
they hide from the heat and sunlight. The only daytime clues to their presence may be chewing damage
to plants and silvery to whitish trails. In mild winter areas of Southern California and coastal locations,
snails and slugs are active throughout the year. During cold weather, snails and slugs hibernate in the
topsoil. During hot, dry periods, snails seal their shell opening with a parchment-like membrane, often
attached to containers, fences, trunks, or walls.
Snails and slugs are hermaphrodites; they have both female and male reproductive parts. But generally
they must mate with another mollusk of the same species in order to lay viable eggs. Brown garden snails
mature in about 2 years, whereas some slugs reach reproductive maturity in about 3 to 6 months.
Brown garden snail is the most common snail pest. It has a spiraling shell up to 1-1/4 inches in diameter.
The shell is patterned brown, gray, tan, and yellow in bands, flecks, and swirls. Where calcium is
abundant in their food or soil, the shells will be hard. However, where calcium is low, shells may be quite
fragile. Adult brown garden snails can lay about 80 eggs per month in shallow depressions in growing
media and topsoil, but clutches (groups of eggs) may be smaller, often 10 to 20 eggs. The spherical to
teardrop-shaped eggs are 1/8 inch in diameter and initially white, but become browner as they develop.
The eggs may be mistaken for certain slow-release fertilizers.
Amber snails have an elongate shell up to 4/5 inch long that is translucent and mostly brown or
yellowish-orange (amber colored). These semiaquatic snails occur mostly in the wetter portions of
growing areas. Several Novisuccinea and Succinea species can be present and they are not reliably
distinguishable to species. These snails generally feed on algae on the bench or pot, but will also feed on
tender leaves and petals.
Cellar glass-snail has a shiny, pale brown, translucent shell up to 1/2 inch wide. The body on top is pale
blue. Cellar glass-snail is an omnivore; its food includes dead and living plants, earthworms, fungi, other
snails and slugs and their eggs, and sowbugs.
White garden snail has coloration and a shell shaped similar to brown garden snail, but overall it is more
pale and smaller at maturity. White garden snails are about 1/2 to 3/5 inch in diameter at maturity, and
rarely grow up to 1 inch. In California this introduced pest is established in San Diego County and has
been found in Los Angeles and Orange counties.
Slugs of various species can be pests in greenhouses and nurseries. These include, garden slug, gray
garden slug (gray field slug, or milky slug), greenhouse slug, threebanded garden slug, and tramp slug.
For more information consult California Pest Snails and Slugs, Slugs: A Guide to the Invasive and Native Fauna
of California, and Terrestrial Mollusc Tool.
DAMAGE
Snails and slugs chew and feed on algae, decaying organic matter, and various living plants. They chew
irregular holes in leaves or entirely clip off succulent plant parts. They sometimes chew flowers, fruit,
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roots, and tender bark. They make shiny to whitish trails on plants and other surfaces where their dark to
pale feces may also be found. Because they prefer humid or moist conditions and prefer to feed on succulent plant parts, they are primarily pests of herbaceous and low-growing plants and seedlings. Quarantines prohibit the sale and shipment among counties and states of plants infested with the introduced
brown garden snail, white garden snail, other exotic snails or slugs, and commonly all mollusks.
MANAGEMENT
Employ a combination of methods for effective snail and slug management:
• Eliminate where feasible the places where snails and slugs can hide during the day. Boards, debris,
stones, leafy branches growing close to the ground, weedy areas, and dense ground covers such as
ivy are ideal sheltering spots. Reducing hiding places allows fewer snails and slugs to survive.
• Inspect regularly the remaining places where slugs and snails seek shelter. The survivors will congregate there for spot control, such as by handpicking. Brown garden snails are often found on nursery
containers. Slugs may be found under containers.
• Switch from sprinkler to drip irrigation to reduce humidity and surface moisture, making the habitat
less favorable for mollusks.
• Where possible, do not grow plants on wooden benches and pallets. These stay moist for a long time,
tend to be good sites for growth of algae on which mollusks feed, and provide snails and slugs places
to hide between the bench or pallet and containers.
Biological Control
Snails and slugs have many natural enemies, including parasitic flies in the families Sciomyzidae and
Phoridae, mites, nematodes, pathogens, Scaphinotus spp. and other predaceous ground beetles, staphylinid beetles such as devil's coach horse (Ocypus olens), and small vertebrates such as birds, snakes,
toads, and turtles. But natural enemies do not provide satisfactory control of mollusks in production
nurseries.
The omnivorous decollate snail (Rumina decollata) is commercially available for biological control of pest
snails in Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino,
San Diego, Ventura, and Tulare counties. Because of the potential impact of the decollate snail on certain
endangered and native mollusks, it cannot be released outside of the above counties.
Decollate snail release in commercial nurseries is not recommended because all plants must be snail-free.
In addition to feeding on other snails, decollate snails feed on some seedlings and succulent, small plants.
Before shipping plants, any decollate and other snails must be removed.
Cultural Control
Carefully inspect new plants and propagation stock to ensure they are pest free. Reduce hiding places
that allow snails and slugs to survive and thrive. Use good sanitation and keep growing areas free of clutter and weeds. Grow plants off the ground and on metal benches and not on anything made of wood.
Switch from overhead irrigation to drip to reduce the wetness of growing areas that favors pest mollusks.
Increase the frequency between irrigations to the extent compatible with good plant growth. Irrigate early
in the day so surfaces are drier by evening when mollusks become active. Apply copper bands or screens
on benches to inhibit the movement of snails and slugs from the ground to plants on benches.
Handpicking.
Handpicking can be very effective if done thoroughly on a regular basis and in combination with
reducing the places where mollusks can hide. Snails and slugs can be controlled and monitored using
trap boards positioned throughout the nursery as discussed below. Crush and dispose of mollusks in
covered containers away from crops. Snails and slugs may also be killed before disposal by dropping in a
bucket with soapy water or diluted ammonia (5 to 10% solution). Do not apply salt to destroy snails and
slugs as salt can increase soil salinity.
Organically Acceptable Methods
Biological and cultural controls are organically acceptable management methods. Bordeaux mixture,
copper sulfate, and iron phosphate are organically acceptable molluscicides.
Chemical Control
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Baits are effective when used properly in combination with cultural management practices. Note that
baits will kill predatory decollate snails if they are present. The active ingredient of most baits is ferric sodium EDTA, iron phosphate, or metaldehyde. Growers report that iron phosphate appears to be more
effective and persistent where humidity is commonly high, plants are watered overhead, or rainfall is
common. Monitor to determine where to apply the bait. In commercial nurseries to be most effective bait
is scattered throughout planting beds and places where snails hide. The timing of any baiting is critical;
baiting is less effective during cold, dry, and hot times of the year because snails and slugs are less active
then. Because snails and slugs are more likely to travel and encounter any bait when soil is moist, apply
bait after an irrigation.
Bordeaux mixture. Properly mixed copper sulfate and hydrated lime mixture (Bordeaux mixture) can be
brushed or sprayed on trunks or bench legs to repel snails and slugs. One treatment should last about a
year. Adding a commercial spreader-sticker may increase the persistence of Bordeaux mixture through
two seasons.
Copper barriers. Slugs and snails will not cross copper unless the surface is fouled with debris or
becomes heavily oxidized. Copper flashing or vertical copper screens can be erected around planting
beds to prevent in-migration of mollusks. The screen should be 6 inches tall and buried several inches
below the soil to prevent slugs from crawling underneath. Copper screens can be placed between the
bench-support legs and the bench to prevent snails and slugs under the bench from reaching the top
where the pots are located. Copper foil or screen wrapped around planting boxes and bench legs can
repel snails for months or longer.
Monitoring and Treatment Decisions
Regularly inspect growing areas for slugs and snails around chewed plants on cloudy, cool, damp days
or around sunrise or sunset. During the day, scout beneath dense foliage, under benches and under and
on pots, in nearby weeds, under edges of nursery mats, and other protected locations that are dark, moist,
and near growing media, organic litter, or the ground. Slugs commonly are found under pots and in
growing media. Snails are commonly found attached to the less-exposed sides of plant containers.
Amber snails tend to remain on the surface of planting medium. Look for these on pot surfaces and
where moist planting medium and dry areas (e.g., the container) meet, generally around the inner lip or
head space of containers.
Snails and slugs seek cover during daylight and can be trapped under slightly raised boards positioned
throughout the nursery. Traps can be made of lumber about of 12 x 15 inches or any convenient size or
similar material. Raise traps off the ground with 1-inch runners to facilitate pest movement to the shaded
underside. After counting and recording the number of mollusks trapped, scrape off snails and slugs
daily and dispose of them by crushing or killing in soapy water or dilute ammonia solution as described
above.
A method of both control and monitoring that is effective for the brown garden snail is to place an
attractive bait (e.g., containing metaldehyde) in small piles strategically around the growing areas.
Nearby snails will be drawn to the bait overnight and will quickly die. The next morning, the number of
dead snails can be counted to help identify locations where snails are most abundant. As with the trapboard method above, repeated over time the use of bait piles allows comparisons of whether brown
garden snail numbers are increasing or decreasing. If dogs wander the nursery, they may feed on and be
poisoned by exposed metaldehyde bait; place the metaldehyde in a way that it is accessible to the snails
but not the dogs, such as in a commercial bait trap.
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Common name
(trade name)
Amount
per acre
REI‡
(hours)
PHI‡
(days)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the
most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a
pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application
timing. Always read the label of the product being used.
A,
IRON PHOSPHATE
(Sluggo Slug and Snail Bait)#
24–44 lb
0
0
MODE OF ACTION GROUP NUMBER1: —
COMMENTS: Can be more effective and persistent during prolonged wet conditions in comparison with metaldehyde. Reapply
as bait is consumed or at least every 2 weeks while snails and slugs are active.
B.
METALDEHYDE
(Durham Ornamental 3.5)
1 lb
12
NA
( Metarex 5)
8–25 lb
12
NA
MODE OF ACTION GROUP NUMBER1: —
COMMENTS: Reapply at 21 day intervals while snails and slugs are active. Broadcast per label instructions; do not apply in
piles or strips unless using as a monitoring method.
C.
METHIOCARB*
(Mesurol 75W)
2 lb/100 gal
24
0
MODE OF ACTION GROUP NUMBER1: carbamate (1A)
COMMENTS: Danger signal word. Can only be applied twice in a cropping cycle. Do not apply or allow to drift to blooming
crops or weeds. Should only be used as a rescue treatment.
D.
SODIUM FERRIC EDTA
(Ferroxx)
5–20 lb
0
0
MODE OF ACTION GROUP NUMBER1: —
COMMENTS: For terrestrial uses only. Do not allow water from treated fields that flooded to enter surface waters or drinking
waters. Do not contaminate water when disposing of equipment wash water or rinse water. Spot apply near pots instead of broadcasting. May damage contacted, succulent leaves.
E.
BORDEAUX MIXTURE#
0.5:0.5:100
1 lb
See label
—
MODE OF ACTION GROUP NUMBER1: Multi-site contact (M 01)
COMMENTS: Apply only as a dilute spray to plant containers and nearby surfaces. Do not mix with microbial pesticides; contact
with bacterial or fungal pesticides prevents efficacy of the microbial products. Can be phytotoxic to plant tissues. For how to prepare Bordeaux mixture see Pest Notes: Bordeaux Mixture. Check copper label to determine if acceptable in organic production.
F.
COPPER SULFATE
(Cuproxat FL)#
1 pt/100 gal
48
—
MODE OF ACTION GROUP NUMBER1: Multi-site contact (M 01)
COMMENTS: Apply only as a dilute spray to plant containers and nearby surfaces. Do not mix with microbial pesticides; contact
with bacterial or fungal pesticides prevents efficacy of the microbial products
G.
COPPER OXIDE
(Nordox)
1 lb/100 gal
24
0
MODE OF ACTION GROUP NUMBER1: Multi-site contact (M 01)
COMMENTS: Apply only as a dilute spray to plant containers and nearby surfaces. Do not mix with microbial pesticides; contact
with bacterial or fungal pesticides prevents efficacy of the microbial products.
‡
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely
entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the
REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group
number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B.
Mode of action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see
their Web site at http://irac-online.org/.
Acceptable for organically grown produce.
Permit required from county agricultural commissioner for purchase or use.
Unknown
1
#
*
—
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SOFT SCALES (5/10)
Black scale: Saissetia oleae
Brown soft scale: Coccus hesperidum
Green shield scale: Pulvinaria psidii
Hemispherical scale: Saissetia coffeae
DESCRIPTION OF THE PEST
Soft scales are typically found on woody and foliage plants. The first nymphal instar is called a crawler
and has functional legs, while the remaining instars are attached to the leaf or twig and (with the exception of green shield scale) do not move. These scales typically have a more conspicuous profile from the
side view compared with armored scales and produce copious honeydew. The protective covering over a
soft scale cannot be separated from its body. Brown soft scale adults are fairly flat in profile, range in
color from yellowish green to brown, and are often spotted or mottled to uniform brown. Hemispherical
scale adults are round, hard, brown, smooth and shiny. Black scale adults are globular and hardened
with ridges on the back that look like the letter "H". Green shield scale, introduced into California in the
early 1990s, has a light yellow-green color as an immature. Female green shield scales produce a mass of
eggs in a cottony ovisac without mating (i.e., reproduction is parthenogenetic and there are no males).
DAMAGE
Soft scales remove sap from plants and cause yellowing of leaves and overall plant decline. Green shield
scale ovisacs and the honeydew excreted by all the soft scales disfigure plants. Honeydew allows the
growth of black sooty mold fungi and attracts ants. Ants may then carry scales to uninfested plants as
well as protect them from natural enemies such as predators and parasites.
MANAGEMENT
Biological Control
The black scale parasite, Metaphycus helvolus, has also been used for control of the closely related hemispherical scale. The mealybug destroyer, Cryptolaemus montrouzieri, is known to be an effective predator
of green shield scale. Green shield scale, however, is a CDFA "B" rated quarantine pest, so plant material
must be entirely free of the scale to be shipped. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Exclusion of windblown crawlers can be accomplished by covering openings to the greenhouse with fine
mesh screens. Prune out and discard heavily infested plant parts. Control ants.
Monitoring and Treatment Decisions
Visual inspection of plants will help locate infestations and may permit localized treatments of hot spots.
The presence of ants climbing on the plant can also indicate a problem with scales. To monitor the
crawler stage, place double-sided sticky tape around stems.
Treatment is generally warranted when scales are present. Optimum treatment timing is when crawlers
are active; however, this can be difficult when there are overlapping, multiple generations. Multiple applications are generally necessary.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
insect growth
regulator
Pesticide
(trade name)
pyriproxyfen
A. (Distance)
s-kinoprene
B. (Enstar II)
Major Insect and Mite Pests
Manufacturer REI1
Valent
12
Wellmark
4
Mode of
action2 Comments
Do not apply more than 2 times per crop7C
ping cycle or per 6 months.
Apply prebloom. Also labeled for low vol3
ume use.
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neonicotinoid
acetamiprid
A. (TriStar 70WSP)
imidacloprid
(Marathon 1G)
B. (Marathon II)
oil3
Apply as a foliar spray.
Cleary
12
4A
OHP
12
4A
(Marathon 60 WP)
OHP
12
4A
clarified hydrophobic
extract of neem oil#
A. (Triact 70)
OHP
4
un
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above. Apply only as a drench.
Do not spray plants under stress. Target
pest must be completely covered with
spray. Check label for list of plants that
can be treated. May cause injury to flowers.
4
horticultural oil
Ultra-Fine Oil
organophosphate
SafTSide
B. JMS Stylet Oil
acephate
A. (Acephate 97UP)
acephate
(Orthene T,
B. T&O Spray)
acephate
C. (PT 1300 Orthene TR)
malathion
D. (various)
1
2
Whitmire Micro-12
Gen
4
Brandt
JMS Farms
4
United Phosphorus
24
—
—
—
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
1B
Valent
24
Whitmire MicroGen
24
1B
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouses only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia,
and some varieties of chrysanthemum.
Can stunt new growth in roses.
1B
An aerosol for greenhouse use only.
various
1B
Not for greenhouse use.
12
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
3
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
4
Check with certifier to determine which products are organically acceptable.
* Restricted use material. Permit required for purchase or use.
#
Acceptable for use on organically grown ornamentals.
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THREAD-FOOTED (TARSONEMID) MITES (5/10)
Broad mite: Polyphagotarsonemus latus
Bulb scale mite: Steneotarsonemus laticeps
Cyclamen mite: Phytonemus pallidus
DESCRIPTION OF THE PESTS
Thread-footed mites are tiny and cannot be readily seen without magnification (20X to 40X). The life
stages of these thread-footed mites are: egg, nymph, pseudopupa, and adult (one less stage than for spider mites). Eggs of the cyclamen mite are one-half the length of the adult and are oval shaped. Eggs of the
closely related broad mite are distinguishable from cyclamen mite eggs by rows of white pegs on the
egg's upper surface. Immature stages of these mites are white.
These mites get the name "thread-footed" from the appearance of the hind pair of legs in the adult female,
which is threadlike; adult males, on the other hand, have stout legs for clasping the female. Adult males
carry female pseudopupae on their back. As soon as the adult female emerges, they mate.
Cyclamen mite is generally found feeding on growing terminals, in buds, or on unfolding leaflets. Their
development is optimal under moderately warm (60° to 80°F) temperatures and high humidity (80 to
90%). Broad mite is similar to cyclamen mite, but is generally found mostly on the undersides of plant
leaves. Mites disperse between plants on air currents and by mechanical transport such as on worker's
clothing. These mites can complete one generation in 7 to 21 days, depending on temperature. Female
bulb scale mites lay up to 28 eggs. Adults are usually found between the scales of the bulb and the neck
region. Bulb mites overwinter in bulbs between the scales, emerging as the leaves grow. They re-enter
bulbs as the bulbs dry in the field. One generation can be completed in about 7 weeks under field conditions.
DAMAGE
Feeding by cyclamen and broad mites is easily recognized on all hosts because affected leaves become
characteristically cupped, dwarfed and thickened, and the internodes are greatly shortened. Broad mite
damage occurs more generally over the plant than cyclamen mite damage. Bulb scale mites feeding in developing shoots can cause longitudinal bronze streaks of discoloration, horizontal cracks, distortion, and
death of leaves and flowers.
MANAGEMENT
Use good sanitation practices and biological and chemical controls to manage thread-footed mites.
Biological Control
Neoseiulus californicus and other species of predatory mites have been used for broad mite and cyclamen
mite control. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because these mites feed on a large variety of plant species, keep production areas free of weeds that can
serve as hosts for mite populations. Carefully inspect plants being brought in to start a new crop to ensure that they are free of pests, and disinfest the plants if needed. Disinfestation can be accomplished by
immersing propagation stock in 110.3°F water for 30 minutes, or treatment at 100% relative humidity and
110.3°F for 1 hour. If hot spots of these mites are found in production areas, consider roguing affected
plants and treating the surrounding plants.
Monitoring and Treatment Decisions
Visually inspect plants for typical damage symptoms as part of a weekly scouting program.
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TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Pesticide
Class
(trade name)
macrocyclic lactone A. abamectin
(Avid 0.15EC)
oil3
A. clarified hydrophobic
extract of neem oil#
(Triact 70)
B. horticultural oil4
(Ultra-Fine Oil)
(SafTSide)
(JMS Stylet Oil)
Manufacturer REI1
Syngenta
12
Mode of
action2 Comments
6
Label permits low-volume application.
OHP
4
un
Whitmire
MicroGen
Brandt
JMS Farms
12
—
4
4
—
—
pyridazinone
A. pyridaben
(Sanmite 75WP)
BASF
12
21A
soap3
A. potash soap#
(M-Pede)
Dow Agro
Sciences
12
—
1
2
3
4
*
#
Do not spray plants under stress. Target
pest must be completely covered with
spray. Check label for list of plants that
can be treated. May cause injury to flowers.
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
Use at least 2 different chemicals between applications of Sanmite. Do not
use fertilizers containing boron or apply
through any type of irrigation system. Do
not exceed 10.67 oz/acre/application.
Must contact insect, so thorough coverage is important. Repeat weekly as
needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or
newly rooted cuttings. Do not add adjuvants.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
Check with certifier to determine which products are organically acceptable.
Restricted use pesticide. Permit require for purchase or use.
Acceptable for use on organically grown ornamentals.
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THRIPS (5/10)
Greenhouse thrips: Heliothrips haemorrhoidalis
Western flower thrips: Frankliniella occidentalis
DESCRIPTION OF THE PESTS
Thrips are tiny insects that have four featherlike wings, each consisting of a thick supporting strut with
fine hairs on the front and hind edges. Thrips go through six life stages: egg, first instar, second instar,
prepupa, pupa, and adult. Thrips insert eggs into plant tissue. The first two instars and the adults feed by
piercing and removing the contents of individual plant cells.
Western flower thrips. This thrips has three color forms that vary in abundance depending on the time of
year. There is a pale form that is white and yellow, except for slight brown spots or blemishes on the top
of the abdomen; an intermediate color form with a dark orange thorax and brown abdomen; and a dark
form that is dark brown. The intermediate form is present throughout the year, but in spring the dark
form predominates while the pale form is most abundant at other times throughout the year. The dark
form is an overwintering form that is usually found in foothill or mountain areas. Its presence in greenhouses in spring indicates thrips are migrating into the houses. Western flower thrips usually feed in enclosed tissues such as flowers, buds, or growing tips. Adults also feed on pollen and on spider mites. The
prepupa and pupal stages take place in the soil beneath infested plants. Females will lay male eggs if unmated and female eggs are produced once mating has occurred. Development times to complete one generation of western flower thrips varies from 11 days (77° to 87°F), to 44 days (50° to 60°F).
Greenhouse thrips. Adult greenhouse thrips are tiny, black, insects with whitish to translucent wings
folded back over their thorax and abdomen. Legs are also a whitish color. Nymphs are whitish to slightly
yellowish in color and produce a globule of fecal fluid at the tip of their abdomen. These globules of fluid
increase in size until they fall off and another one begins to form, resulting in a characteristic spotting of
the infestation area with black specks of fecal material.
DAMAGE
Western flower thrips primarily feeds on flowers but also sometimes on new vegetative growth, whereas
greenhouse thrips feeds primarily on foliage. Direct feeding damage includes streaking, spotting, and tissue distortion. On leaves, feeding often occurs along veins and appears as an outlining of the veins. Western flower thrips can vector Tomato spotted wilt virus as well as many other viruses. Western flower thrips
may cause premature senescence of flowers, such as African violets, because they prematurely pollinate
the flowers. On orchids, western flower thrips feeding and egg laying will leave translucent 'pimpling'
spots on petals and leaves. Greenhouse thrips stipple the foliage of numerous field and greenhouse
grown plants. The stippling damage caused by thrips feeding on individual cells is often confused with
mite stippling. Thrips feeding is often accompanied, however, by black, varnishlike flecks of dried excrement whereas mite stippling is often accompanied by webbing or shed skins.
MANAGEMENT
Prevention is a good strategy in a thrips management program. Treat plants with an effective insecticide
and move them to a holding area for inspection and potting.
Biological Control
Three commercially available predators to help control western flower thrips are the minute pirate bug,
Orius tristicolor, and two predatory mites, Neoseiulus cucumeris, and Hypoaspis miles. Minute pirate bugs
are polyphagous and will also feed on aphids, mites, and small caterpillars. Orius are released at a rate of
2000 to 4000 per acre, while Neoseiulus cucumeris are released at a rate of 10 to 50 mites per plant for each
of 2 to 3 weeks. These mites will also feed on spider mite eggs, pollen, and fungi. Hypoaspis miles are soilinhabiting predators that feed on thrips prepupae and pupae in the soil. These mites are generally released in the soil at planting and are most successful at controlling thrips when there is plant-to-plant
contact that facilitates movement of the predators between plants. A commercially available parasite of
greenhouse thrips is Thripoctenus javae =Thripobius semiluteus. For more information, see BIOLOGICAL
CONTROL.
Cultural Control
Because western flower thrips and greenhouse thrips feed on a large variety of plant species, keep production
areas free of weeds, which can serve as hosts for thrips populations. Most commercially available screens
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have pore sizes slightly larger than the width of the western flower thrips thorax (145 microns), meaning that
some winged adults can penetrate these openings. However, covering openings to the greenhouse with fine
screens does exclude most thrips. Be sure that the ventilation system on an existing greenhouse can accommodate the reduced flow caused by a fine screen or else the system will need to be modified.
Monitoring and Treatment Decisions
Blue sticky cards are most attractive to western flower thrips. However, yellow cards are good predictors
of western flower thrips populations, are easier to count and are more commonly used for general-purpose insect monitoring. Place yellow sticky cards vertically in the crop canopy, with the lower one-third
of the trap in the leaves and the upper two-thirds above the leaves. As the crop grows, the traps will need
to be raised. For more information, see MONITORING WITH STICKY TRAPS.
There is little research on the most effective trap density to use or on action thresholds. Research in California greenhouse roses suggests that three traps per cultivar is adequate. In greenhouses with many different cultivars, place traps in the most sensitive varieties, usually yellow or white flowers. In large greenhouses of the same or similar cultivars, there should be at least eight traps per 100,000 square feet. The
treatment threshold for roses is 25 to 50 thrips per card per week (25 for more sensitive yellow- and
white-flowered varieties, 50 for reds). In other crops place one card per 10,000 square feet. Consider treating if an average of 5 to 10 thrips per card per week is present.
It is important to note that correct identification of pest thrips is essential in a monitoring program. There
may be several species of thrips present on a sticky card but only the western flower thrips and greenhouse thrips should be counted when making treatment decisions.
Most insecticides must be applied at least two times, 5 to 7 days apart, for efficacy against western flower
thrips.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
Pesticide
(trade name)
Manufacturer REI1
Mode of
action2 Comments
biological
A. Beauveria bassiana#
(BotaniGard 22WP)
(BotaniGard ES)
Laverlam
4
—
botanical
A. cinnamaldehyde
(Cinnacure)
Proguard
4
—
B. pyrethrin/PBO3
(PT Pyrethrum TR)
Whitmire
MicroGen
12
3/—
A. methiocarb*
(Mesurol 75W)
Gowan
24
1A
OHP
4
un
(Ornazin 3%EC)
B. novaluron
(Pedestal)
SePRO
Chemtura
12
12
un
15
A. abamectin
(Avid 0.15EC)
Syngenta
12
6
carbamate
insect growth regula- A. azadirachtin
tor
(Azatin XL)
macrocyclic
lactone
Major Insect and Mite Pests
Treat every 7 days while insects are active. Do not tank mix with most fungicides
and wait 48 hours after application to apply a fungicide.
Use product within 10 days of breaking
seal. Do not apply to stressed plants or
newly transplanted material before roots
are established.
An aerosol synthetic pyrethroid that is
some-times used as an irritant when
mixed with other pesticides.
Apply in 50 gal water. Repeat as necessary up to 4 applications/season. Do not
apply with oil or foliar fertilizer. Do not
use through any type of irrigation system.
Must contact insect. Repeated applications as necessary. Label permits lowvolume application.
Do not exceed 22.5 oz/acre/application
Use no more than twice per year and
don't exceed 52 oz/acre/year. Don't use
on poinsettia.
Label permits low-volume application. Do
not use through any type of irrigation system.
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neonicotinoid
A. acetamiprid
(TriStar 70WSP)
B. imidacloprid
(Marathon 1G)
(Marathon II)
Cleary
12
4A
OHP
12
4A
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
As above, but apply only as a drench.
Must contact insect. Repeat applications
as necessary. Difficult to get coverage in
flowers, best for thrips on foliage.
(Marathon 60 WP)
4
oil
A. clarified hydrophobic
extract of neem oil#
(Triact 70)
OHP
4
un
organophosphate
A. acephate
(Acephate 97UP)
B. acephate
(Orthene T,
T&O Spray)
United Phosphorus
Valent
24
1B
24
1B
C. acephate
Whitmire Mi(PT 1300 Orthene TR) croGen
A. potash soap#
(M-Pede)
Dow Agro
Sciences
24
1B
12
—
A. spinosad
(Conserve SC)
4
5
soap4
spinosyn
1
2
3
4
*
#
Dow Agro
Sciences
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
greenhouses only labeled for use on anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia,
and some varieties of chrysanthemum.
Can stunt new growth in roses.
An aerosol for greenhouse use only.
Must contact insect, so thorough coverage is important. Repeat weekly as
needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or
newly rooted cuttings. Do not add adjuvants.
Do not apply more than 10 times in a 12month period. Compatible with most beneficials, but highly toxic to bees and hymenopteran parasites. Direct contact can
cause significant mortality to Phytoseiulus
persimilis.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
PBO = piperonyl butoxide
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
Restricted use material. Permit required for purchase or use.
Acceptable for use on organically grown ornamentals.
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TWOSPOTTED SPIDER MITES (5/10)
Tetranychus urticae
DESCRIPTION OF THE PEST
Twospotted spider mites are web-forming mites that pierce plant cells and remove their contents. All spider mites have two body segments and four pairs of legs as adults. Twospotted spider mite adults, as the
name suggests, have two large dark spots on the sides of their yellowish green bodies. These mites lay
round eggs that hatch into six-legged larvae. The subsequent stages, the protonymph and deutonymph
stages, are eight-legged as are the adults. Since the entire life cycle can take as little as 8 (77° to 95°F) to 28
(50° to 68°F) days, spider mites have many generations per year and can rapidly increase in number.
DAMAGE
Twospotted mites suck cell contents from leaves, initially stippling leaves with a fine pale green mottling.
As feeding continues, the stippling increases and leaves turn yellow with bronzed or brown areas; damaged leaves frequently fall. Undersides of leaves may have many cast skins of mites, and the webbing on
foliage is unaesthetic. Plants may become severely stunted when large mite populations are allowed to
feed and the plants may die.
MANAGEMENT
Biological Control
Many different species of predatory mites are available for control of these mites under different conditions. Phytoseiulus persimilis is a commercially available predator of twospotted spider mite, and it has
been used to control mite populations in greenhouses and field situations. It can reproduce faster than its
prey, yet best results have been obtained when it is released into the crop well before the spider mite populations have built up. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because spider mites feed on a large variety of plants, keep production areas free of weeds, which can
serve as hosts to the mites. Carefully inspect plants being brought in to start a new crop to ensure that
they are free of mites. Rogue or treat infested plants.
Monitoring and Treatment Decisions
Monitor the crop regularly, as indirect sampling methods (such as sticky cards) are ineffective. Observe
the undersides of leaves with a 10X hand lens, and watch for changes in plant foliage that are characteristic of mite feeding.
Except as noted, the materials listed only kill active stages of mites, so more than one treatment may be
necessary to break the life cycle. Follow label directions regarding reapplication times. For guidelines on
when to treat, see ESTABLISHING ACTION THRESHOLDS.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
Pesticide
(trade name)
Manufacturer REI1
Mode of
action2 Comments
botanical
A. cinnamaldehyde
(Cinnacure)
Proguard
4
—
carbamate
A. methiocarb*
(Mesurol 75W)
Gowan
24
1A
Gowan
12
carboximide
A. hexythiazox
(Hexygon 50DF)
Major Insect and Mite Pests
Use product within 10 days of breaking
seal. May cause phytotoxicity to tender
tissue growth on plants. Do not apply to
stressed plants or newly transplanted
material before roots are established.
Apply in 50 gal water. Repeat as necessary up to 4 applications/season. Do not
apply with oil or foliar fertilizer.
10A
No chemigation. Ovicidal/larvicidal action.
Use only 1 time per crop or once a year.
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carboxylic acid
A. bifenazate
(Floramite)
Chemtura
12
un
macrocyclic lactone A. abamectin
(Avid 0.15EC)
Novartis
12
6
oil3
OHP
4
un
Do not spray plants under stress. Target
pest must be completely covered with
spray. Check label for list of plants that
can be treated. May cause injury to flowers.
Whitmire MicroGen
Brandt
JMS Farms
12
—
4
4
—
—
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
A. clarified hydrophobic
extract of neem oil#
(Triact 70)
B. horticultural oil4
(Ultra-Fine Oil)
(SafTSide)
(JMS Stylet Oil)
Do not use in successive applications; apply at least two alternative products between treatments of bifenazate. Primarily
effective against motile stages but has
some ovicidal activity.
Label permits low-volume application.
phenoxypyrazole
A. fenpyroximate
(Akari)
SePRO
12
21A
Do not apply more than 10 gal spray/1000
sq ft/application. Do not exceed 48
oz/crop cycle or growing season, whichever is longer.
pyrethroid
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
C. fenpropathrin*
(Tame 2.4EC Spray)
D. fluvalinate
(Mavrik Aquaflow)
Whitmire
MicroGen
Whitmire
MicroGen
Valent
12
3
12
3
Check label. A fogger for greenhouse use
only.
Label permits low-volume application.
24
3
Label permits low-volume application.
Wellmark
12
3
pyridazinone
A. pyridaben
(Sanmite 75WP)
BASF
12
21A
pyrrole
A. chlorfenapyr
(Pylon)
A. potash soap#
(M-Pede)
OHP
12
13
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Use at least 2 different chemicals between applications of Sanmite. Do not use
fertilizers containing boron. Do not exceed
10.67 oz/acre/application.
Greenhouse use only. Do not exceed 3
applications/growing cycle.
Dow Agro
Sciences
12
—
soap3
spinosyn
1
2
A. spinosad
(Conserve SC)
Dow Agro
Sciences
4
5
Must contact mite, so thorough coverage
is important. Repeat weekly as needed up
to 3 times. Test for phytotoxicity. Do not
spray new transplants or newly rooted
cuttings. Do not add adjuvants.
Miticidal activity of this material is due
mainly to the surfactants and other inert
ingredients. This material is not recommended for use against mites unless
control is also needed for other pests
(caterpillars, leafminers, thrips) against
which the active ingredient in this product is effective. Do not apply more than
10 times in a 12-month period. Compatible with most beneficials but highly toxic
to bees and hymenopteran parasites.
Direct contact can cause significant
mortality to Phytoseiulus persimilis.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should
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3
4
*
#
be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
Check with certifier to determine which products are organically acceptable.
Restricted use pesticide. Permit require for purchase or use.
Acceptable for use on organically grown ornamentals.
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WHITEFLIES (5/10)
Greenhouse whitefly: Trialeurodes vaporariorum
Silverleaf whitefly: Bemisia argentifolii (=Bemisia tabaci B-biotype)
DESCRIPTION OF THE PESTS
Greenhouse whitefly. The greenhouse whitefly adult is 0.9 (male) to 1.1 mm (female) long, with four
wings, sucking mouthparts, a powdery waxy coating over the body, and wings that give the otherwise
yellow body a white color. The wings are held nearly parallel to the leaf and cover the abdomen when the
adult is at rest. There are seven life stages: egg, four nymphal instars, pupal stage, and the adult. Females
occasionally lay eggs in circles on the undersides of leaves of plants with smooth leaves. Egg laying on
plants with pubescent leaves results in random placement of the eggs. Eggs are partially inserted into the
leaf, initially they are yellowish, but close to hatching they turn a purplish brown. The first nymphal instar is called a crawler and has functional legs, while the remaining instars are attached to the underside
of the leaf and do not move. The end of the fourth instar is called a pupa. The pupal stage is the most important for determining whitefly species identification. Greenhouse whitefly pupae are oval and have
vertical sides, giving the pupa a cakelike appearance from the side. Along the perimeter of the upper surface is a fringe of filaments and relatively large wax filaments project above the upper surface of the
body. The greenhouse whitefly can complete one generation in 21 to 26 days at 81°F.
Silverleaf whitefly. The silverleaf whitefly adult is 0.8 (male) to 1.0 mm (female) long, with four wings,
and sucking mouthparts. The white, waxy coating covering its body and wings is not as thick as it is on
the greenhouse whitefly and its yellow body has a whitish hue from the wax rather than a white color.
The wings are held at the sides of the body, partially exposing the back of the abdomen when the adult is
at rest. There are seven life stages: egg, four nymphal instars, pupa, and the adult. Eggs are not laid in a
circular pattern, are partially inserted into the leaf, and remain yellowish until they hatch. The first nymphal instar is called a crawler and has functional legs, while the remaining instars are attached to the leaf
and do not move. The end of the fourth instar is called a pupa. Silverleaf whitefly pupae are ovoid, but
with a slightly pointed hind end and red eye spots easily visible from above. The pupa is fairly flat and
does not have a marginal fringe of filaments. The length of wax filaments projecting above the upper surface of the body varies on different hosts. Silverleaf whiteflies can complete development in 16 (86°F) to
31 (68°F) days.
DAMAGE
Whitefly adults and immatures feed on sap. As they feed, they excrete honeydew, a sticky substance that
causes unsightly glistening and supports the growth of black sooty mold. Very large populations of
whiteflies cause stunting of plant growth, and leaves may senesce and die. Physiological abnormalities,
such as white stem on poinsettia, may also occur. Usually populations are not high enough to stunt ornamentals, and damage is mostly caused by honeydew, sooty mold, and nuisance populations of flying
adults.
MANAGEMENT
Biological Control
Encarsia formosa, a tiny, stingless parasitic wasp, is as an effective biological control for greenhouse whiteflies. Wasps are released once a week at a rate of two to five parasites per plant for 8 to 10 weeks of the
growing season. This sort of release program can be effective if long residual insecticides have not been
applied in advance of the parasite release, and where the initial population of whiteflies is quite low (only
a few whiteflies per plant). Greenhouse whitefly pupae turn black when parasitized by Encarsia, which
emerge as adults through circular exit holes. Delphastus pusillus, a whitefly predator, has been used
against silverleaf whiteflies. Eretmocerus eremicus is a commercially available whitefly parasite for silverleaf whitefly. It will also attack greenhouse whitefly, whereas Encarsia is ineffective against silverleaf
whitefly. For more information, see BIOLOGICAL CONTROL.
Cultural Control
Because whiteflies feed on a large variety of plant species, keep production areas free of weeds, which
can serve as hosts for whitefly populations. Exclusion of winged adults can be accomplished by covering
openings to the greenhouse with screens that have a pore width of 405 microns or smaller.
Before starting a new crop, carefully inspect plants to ensure that they are free of whiteflies and other
pests. Treat or discard any infested plants.
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In open field production, mulching with silver reflective plastic has been shown to repel whiteflies, thus
greatly reducing their presence in and around the plant canopy. Apply the plastic mulch at the time of
planting or transplanting for best results. In addition to repelling insects and reducing the incidence of
insect-transmitted diseases, reflective mulch may increase plant growth, cut-flower yield, and reduce the
irrigation water and fertilizer requirement. This control method is acceptable for organic production.
Monitoring and Treatment Decisions
Yellow sticky cards placed in greenhouses will capture adult whiteflies. However, traps need to be used
at a greater density, one per 1,000 sq. ft., than for other pests. Trap monitoring should be supplemented
with inspection of leaves for nymphs and pupae. When monitoring plant samples, it is imperative to look
on the undersides of leaves for adults and nymphs. For more information, see MONITORING WITH
STICKY TRAPS.
Treatment thresholds vary with the crop. For example, cut flowers such as gerberas can tolerate more
whiteflies than poinsettias because only the flowers are harvested in the cut flower crop whereas the entire poinsettia plant is marketed. For more information, see ESTABLISHING ACTION THRESHOLDS.
TREATMENT
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the
first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
Class
biological
Pesticide
(trade name)
A. Beauveria bassiana#
(BotaniGard 22WP)
B. (BotaniGard ES)
A. pyrethrin/PBO3
(PT Pyrethrum TR)
insect growth regula- A. azadirachtin
(Azatin XL)
tor
botanical
Manufacturer REI1
Laverlam
4
Laverlam
4
Whitmire Micro-12
Gen
OHP
4
Mode of Comments
action2
—
Treat every 7 days while insects are active. Do not tank mix with most fungicides
and wait 48 hours after application to apply a fungicide.
—
3/—
An aerosol.
un
Must contact insect. Repeat applications
as necessary. Label permits low-volume
application.
Do not exceed 22.5 oz/acre/application.
B. azadirachtin
(Ornazin 3%EC)
C. diflubenzuron
(Adept 25WP)
SePRO
12
un
Chemtura
12
15
Whitefly suppression. May damage poinsettias if used over labeled rate. Also effective on fungus gnat larvae and lepidopteran larvae.
D. novaluron
(Pedestal)
Chemtura
12
15
Use no more than twice per year and
don't exceed 52 oz/acre/year. Don't use
on poinsettia.
E. pyriproxyfen
(Distance)
F. s-kinoprene
(Enstar II)
Valent
12
7C
Wellmark
4
7A
Do not apply more than 2 times per cropping cycle or per 6 months.
Apply prebloom. Also labeled for low volume use.
Syngenta
12
6
Cleary
12
4A
OHP
12
4A
macrocyclic lactone A. abamectin
(Avid 0.15EC)
neonicotinoid
A. acetamiprid
(TriStar 70WSP)
B. imidacloprid
(Marathon 1G)
(Marathon II)
Major Insect and Mite Pests
Label permits low-volume application.
Not to be used more than once every 16
weeks. Do not apply to soils that are water logged or saturated. Do not apply to
bedding plants intended to be used as
food crops.
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oil4
organophosphate
pyrethroid
pyridazinone
pyridine
soap4
1
2
3
4
(Marathon 60 WP)
A. clarified hydrophobic
extract of neem oil#
(Triact 70)
OHP
12
4
4A
un
B. horticultural oil5
(Ultra-Fine Oil)
(SafTSide)
(JMS Stylet Oil)
A. acephate
(Acephate 97UP)
As above. Apply only as a drench.
Do not spray plants under stress. Target
pest must be completely covered with
spray. Repeat application as necessary.
Check label for list of plants that can be
treated. May cause injury to flowers.
Use as above for neem oil. Also, do not
use with sulfur fungicides; check label for
tank mix restrictions.
Whitmire
MicroGen
Brandt
JMS Farms
United
Phosphorus
12
—
4
4
24
—
—
1B
B. acephate
(Orthene T, T&O
Spray)
Valent
24
1B
C. acephate
(PT 1300 Orthene TR)
D. malathion
(various)
A. bifenthrin
(Attain TR)
B. bifenthrin*
(Talstar Professional)
Whitmire
MicroGen
various
24
1B
A number of chrysanthemum varieties
have exhibited phytotoxic reactions. In
the greenhouse, only labeled for use on
anthurium, cacti, carnation, rose, orchids,
some foliage plants, young poinsettia and
some varieties of chrysanthemum. Can
stunt new growth in roses.
An aerosol for greenhouse use only.
12
1B
Not for greenhouse use.
Whitmire
MicroGen
FMC
12
3
12
3
Check label. A fogger for greenhouse use
only.
Label permits low-volume application.
C. cyfluthrin
(Decathlon 20WP)
D. fenpropathrin*
(Tame 2.4EC)
E. fluvalinate
(Mavrik Aquaflow)
OHP
12
3
Label permits low-volume application.
Valent
24
3
Label permits low-volume application.
Wellmark
12
3
F. permethrin
(Astro)
FMC
12
3
Label permits low-volume application.
Also labeled as a cutting dip at 5 fl oz/100
gal.
Direct application to blooms may cause
browning of petals. Marginal leaf burn
may occur on salvia, dieffenbachia and
pteris fern. Label permits low-volume application. Do not apply more than 2 lb
a.i./acre/year.
A. pyridaben
(Sanmite 75WP)
A. pymetrozine
(Endeavor)
BASF
12
21A
Syngenta
12
9B
A. potash soap#
(M-Pede)
Dow Agro
Sciences
12
—
Apply as foliar spray at 7-14 day intervals. For outdoor use, do not apply more
than 48 oz/acre/year; for indoor use, do
not use more than 100 oz.
Must contact insect, so thorough coverage is important. Repeat weekly as
needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or
newly rooted cuttings. Do not add adjuvants.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.
Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to
help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated
with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
PBO = piperonyl butoxide
Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.
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5
*
#
Check with certifier to determine which products are organically acceptable.
Restricted use pesticide. Permit required for purchase or use.
Acceptable for use on organically grown ornamentals.
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Nematodes
(Section reviewed 3/21)
Foliar nematodes: Aphelenchoides fragariae and A. ritzemabosi
Root-knot nematode: Meloidogyne spp.
DESCRIPTION OF THE PESTS
Nematodes are typically tiny (usually microscopic), unsegmented roundworms. At maturity, they commonly are 1/100 to 1/25 inch (0.25 to 1 mm) long. Depending on the type of nematode, they feed on or
inside bulbs, leaves, seeds, stems, or roots. Root-knot nematodes (Meloidogyne spp.) are the most prevalent nematodes attacking floricultural and nursery crops. Foliar nematodes (Aphelenchoides spp.) and lesion nematodes (Pratylenchus spp.) can also cause problems. However, there are numerous other nematodes, both ectoparasitic (feed externally on plants) and endoparasitic (enter plant tissues to feed and reproduce) that can attack floricultural and nursery crops. Because growing media used in containers is
commonly pasteurized, soil-dwelling nematodes primarily cause problems in field crops.
Plant-parasitic nematodes generally hatch from an egg and develop through four juvenile stages before
maturing into adults. Most species are active at temperatures from about 60° to 85°F. Feeding stages
pierce plant cells and withdraw the contents. They also inject enzymes and other chemicals that breakdown cells and can change the appearance and physiology of plants. Tissues injured by nematode feeding become increasingly susceptible to infection by pathogenic bacteria, fungi, and oomycetes. Certain
species of plant-parasitic nematodes vector some plant viruses.
Root-knot Nematodes
Root-knot nematodes occur throughout California and most of the United States. The second-stage larvae
occur in soil, are mobile, and can enter roots. Once inside the roots, they become immobile near vascular
cells where they induce feeding sites (giant cells). While the root swells to form galls, within those structures the nematodes further develop through three molts into mature females. Each of those pear-shaped
females can produce up to 400 eggs in a protective gelatinous mass that protrudes from the surface of
roots. Second-stage larvae hatch from eggs to repeat the cycle, or eggs can remain viable in the soil and
hatch during the next crop or growing season. The time from root invasion to egg development is determined mostly by temperature, but also depends on the nematode species and host crop.
Root-knot nematodes are the most common pests of plants grown in warm, sandy, irrigated soils. The
particular Meloidogyne species that are active can depend on cropping history, geographical location, and
seasonal temperature. Although Meloidogyne species generally have a broad host range, there are differences between species, so cropping history can influence the species of root-knot nematodes present. See
the University of California (UC), Davis Nemaplex website for more information.
To tentatively diagnose an infestation, dig the plants up after they have grown for about 4 to 6 weeks in
soil above 65°F. Wash or gently tap the soil from their roots and examine the roots for swellings and
gnarled, restricted root growth. Cut open any galls and use a hand lens or binocular microscope to examine galls for the presence of pinhead-sized, shiny white females that look like tiny pearls. For confirmation of infection by root-knot nematodes, send roots or soil or both to a nematology laboratory.
Foliar Nematodes
Foliar nematodes, also called bud and leaf nematodes, prefer moderate temperatures and moist or humid
conditions. Aphelenchoides fragariae and A. ritzemabosi are the leaf-infesting nematodes that attack ornamental plants in California. Ferns, strawberries, tropical foliage plants, and vegetatively propagated ornamentals are important hosts of A. fragariae. Foliar nematode damage in California occurs mostly in certain
greenhouses and in fields along coastal areas where humidity is high and ornamental hosts and strawberries are grown. Foliar nematodes are tiny, about 1/50 to 1/25 inch (0.5–1 mm) long, and samples must be
sent to a nematode diagnostic laboratory to confirm an infestation.
Foliar nematodes infest new plants by swimming in a water film up stems and along the surface of moist
plant tissue. After entering leaves through stomata, females lay their eggs in intracellular spaces in leaves.
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Foliar nematodes can mature from egg to adult in about 2 weeks, allowing many generations to develop
during one growing season. Foliar nematodes can also live for a few months in soil or decomposing organic material by feeding on fungi. They typically overwinter in dormant buds, plant terminals, and soil
in dead leaves that drop from infested plants. In slowly drying leaf tissue, adults of A. ritzemabosi can enter a desiccated, resting stage that allows them to survive for several years until moist conditions induce
them to resume activity. See the UC Davis Nemaplex website for more information.
To make an initial diagnosis, tear symptomatic tissue into small pieces and place it in a glass dish. Add
just enough water to immerse the plant tissue, then cover the dish to reduce evaporation. After 24 hours,
carefully examine the water under strong light using a 10X hand lens or, preferably, a binocular microscope providing higher magnification. Nematodes will appear as tiny strands moving in the water.
SYMPTOMS AND DAMAGE
Root-knot nematodes
Root-knot nematodes cause galls or swellings on the roots of many broadleaf plants. Many weeds host
root-knot nematodes. Some grasses and cereals (monocots) can be infested and are suitable hosts, but root
symptoms (galls) on these crops are generally not obvious. Severely infected roots may subsequently be
attacked by a variety of decay- or disease-causing microorganisms, including bacteria, fungi, and oomycetes. Aboveground symptoms are usually nonspecific, characteristic of a poorly functioning root system,
and may include stunted growth, wilting, and yellowing.
Although beneficial nitrogen-fixing bacteria often form nodules on the roots of legumes such as cassia,
sweet pea, and vinca, these nodules rub off roots easily, whereas galls caused by root-knot nematodes are
truly swellings of the roots. Also, a thumbnail can easily be pressed into a bacterial gall, but not into a gall
of root-knot nematodes. To provide identification, collect galled roots and surrounding soil and send
them to a nematode diagnostic laboratory.
Foliar nematodes
Foliar nematode damage can be confused with symptoms caused by certain bacteria, fungi, viruses, nutrient deficiencies, or chemical injuries. Nematodes may interact with certain bacteria or fungi to cause severe foliar blight.
Foliar nematode damage usually begins as yellowish leaf spots that eventually turn dark green to blackish brown. Discoloring typically starts near the leaf base and spreads outward. The lesions are often angular because nematodes in leaves are initially contained between the veins. Because monocots have parallel veins, discoloring on them occurs in streaks.
If young leaves or shoots are infested, they may remain undersized, become bushy or distorted, and produce little or no marketable foliage or flowers. Damaged foliage may become brittle or shrivel and drop
prematurely. Damage usually appears beginning in spring (or winter in coastal areas) and becomes most
severe by summer.
SAMPLING NEMATODES
The best time to sample nematodes for the next crop is at or around the harvest of the current crop when
plants with damage symptoms are available for testing. Nematodes of most pest species are usually concentrated near or in plant roots. Unless your nematology laboratory recommends other procedures, the
following method can be used. Divide the field into areas of uniform plant growth and similar soil characteristics and cropping history. Take several soil subsamples from locations scattered throughout each
uniform field area. Each subsample can be about 1 pint of soil. Collect moist (not soggy) soil from the
plant root zone or the upper 6 to 18 inches of soil if no crop is present. Thoroughly mix the subsamples to
make a composite sample and send about 1 pint of soil for testing. Repeat this sampling procedure for
each field area. If plants have symptoms, dig them up along with their roots and surrounding soil and
place them in a bag for testing. Also, bag separately at least one or two plants and soil sampled from a
healthy-looking part of the field and send them for comparison testing.
Label each sample with field location, current crop, cropping history, crop injury observed, and your
name, address, and phone number. Seal samples in plastic to prevent them from drying out and keep
them cool at about 50° to 60°F until the material reaches the laboratory. Laboratories should report the
genus of the nematodes that were found, the number of nematodes per unit of soil, and the extraction
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efficiency. It is important to know the laboratory's method (and the method's efficiency) for extracting
nematodes from soil. Certain techniques are not adequate for detecting the presence of specific genera of
nematodes, or they provide only qualitative results, which tell you that nematodes are present but not
whether they are abundant enough to cause damage.
MANAGEMENT OF FOLIAR NEMATODES
Grow plants in soilless media or pasteurize media before use. Propagate only nematode-free stock. Foliar
nematodes are typically introduced into growing areas in cuttings, seedlings, and other vegetative propagation material that may be asymptomatic. Take cuttings only from the tops of long, vigorous growth to
reduce the likelihood that it is infested.
If the plants tolerate heat without damage, cuttings can be disinfected by dipping them in hot water at
122°F for 5 minutes or at 111°F for 30 minutes. Foliar nematodes infesting Easter lilies may be controlled
by dipping bulblets in 125°F water for 10 minutes before planting. However, treatment at the same temperature for 20 minutes results in severe damage to the crop. Thus, to avoid damage to plants, it is critical
to control both temperature and exposure time accurately.
Employ proper sanitation by removing plant debris, promptly disposing of all infested plants, and eliminating weeds that can host foliar nematodes (e.g., goldenrod, groundsel, and sneezeweed) from around
growing areas. To reduce the risk that foliar nematodes will spread throughout the crop by traveling in a
water film on plant surfaces, avoid crowding plants and using overhead irrigation .
MANAGEMENT OF ROOT KNOT AND OTHER SOIL-DWELLING NEMATODES
Rotating crops, employing good cultural practices and excellent sanitation, pasteurizing growing media,
and fumigating field soil before planting are the most important strategies for preventing and managing
most soil-dwelling nematodes. Soil amendments and biological control products may sometimes suppress nematode populations. Post-plant nematicides for use in soil around established plants may be permissible (check the label). But it is generally more effective to employ preventive measures before planting.
Sanitation and Cultural Practices
Avoid introducing nematode-infested plants into growing areas. To minimize the risk of introducing
nematodes with the planting stock, use only good-quality stock from a reliable supplier and, if available,
from participants in the California Department of Food and Agriculture (CDFA) Nursery Services Program. Use growing media known to be free of nematodes or pasteurize growing media before use. Dispose of infested plants when found and avoid moving soil from around infested plants to healthy plants.
Do not allow irrigation water from around infested plants to run off onto healthy plants, as this spreads
nematodes.
Unless the soil is treated first, do not plant susceptible crops in field soils where nematodes have previously been a problem. In particular, do not replant the same plant genera into the old site; rotate crops by
replanting with different genera more tolerant of, or resistant to, the specific nematodes present.
Provide crops with proper cultural care so that they are vigorous and better able to tolerate feeding by
nematodes and other pests. More frequent irrigation of drought-stressed plants can reduce damage
caused by root-knot nematodes, but it does not reduce the abundance of nematodes.
Heat Pasteurization
Pasteurizing media with heat, such as aerated steam, can control nematodes and other pests or pathogens
in container mix and greenhouse beds. Special tractor-drawn steam rakes are available, but except for
raised beds, steam is difficult to use in field soils. The heat generated by decomposer microorganisms
during composting of container media can control certain nematodes, but preparing pathogen-free compost requires careful management and monitoring.
Solarization
In sunny, warm climates, field solarization before planting can temporarily reduce nematode populations
in the upper 12 inches of soil. Solarization involves covering moist, bare soil or container mix with single
or double layers of clear plastic for several weeks during hot weather. In some cases, incorporating
amendments (such as compost or green manure) or applying lower than normal rates of fumigant
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pesticides in combination with solarization can provide better control than using any single method. Correct use of "double-tent" solarization can completely eradicate plant-parasitic nematodes, most other
pathogens, and weed seeds from containerized growth media. See the table of Some Flower and Nursery
Crop Nematodes Controlled by Solarization of Container Mix for which nematodes are controlled in this
situation. See CDFA's Nursery Inspection Procedures Manual (NIPM Item 7) and UC's Using Solarization
to Disinfect Soil for Containerized Production (PDF) for details.
Some Flower and Nursery Crop Nematodes Controlled by Solarization of
Container Mix
Common name
Scientific name
citrus
Tylenchulus semipenetrans
dagger
Xiphinema spp.
ring
Criconemella (=Criconemoides) xenoplax
root knot
Meloidogyne hapla
root knot
Meloidogyne incognita
root knot
Meloidogyne javanica
root lesion
Pratylenchus spp.
stem and bulb
Ditylenchus dipsaci
Source: Stapleton, J., L. Ferguson, and M. McKenry. 1998. Using solarization to disinfect soil for
containerized production (PDF). U.C. Plant Protection Qtr. 8(1 & 2): 7-9
(https://ucanr.edu/sites/kac/files/123909.pdf).
Hot Water Dips
Hot water dips can reduce the number of nematodes and certain other pests infesting bulbs, corms, and
rhizomes of crops such as amaryllis, daffodil, gladiolus, lily, and tulip. The temperature and time needed
to provide sufficient control depend on the nematode species and crop variety. Exceeding the proper
temperature or exposure time can damage plants, but insufficient temperatures or exposure time may not
kill the nematodes. Cool plants immediately afterward with clean, cold water, then dry thoroughly in
warm air or sunshine. Consider making a fungicide application after the heat treatment. After heat treatment, store the plant material under cool, low-humidity conditions until plants are used.
Amendments and Biological Control
Although amendments and biological control microorganisms reduce plant-parasitic nematodes in certain situations, sufficient control has been unreliable. The reasons for this variable effectiveness are not
well known. To provide a basis for comparison, growers using amendments and biological control products should consider leaving several randomly selected areas of their fields untreated or treated with
more conventional methods or both.
Soil amendments used for nematode control can be placed into four categories: animal-based, inorganics,
plant-based, and microbial. Except for inorganics (such as ammonium sulfate fertilizer and powdered
rock), nematode suppression from most amendments is at least partly the result of biological control. Incorporating animal manure, compost, crop residue, and organic fertilizers increases the organic matter
content of the soil. It improves water and nutrient availability to plants, reduces plant stress, and can encourage higher numbers of nematode predators and parasites. Some residues can produce by-products
with nematicidal properties upon degradation. However, organic amendments sometimes contain contaminants such as weed seeds, especially in non-composted or incompletely composted materials, and
their effectiveness is largely limited to the depth of material incorporation.
Barley, certain legumes such as clover and vetch, French marigold, perennial rye, and other plants with
bioactive properties are grown as crop rotations, cover crops, or trap crops in some row crops. These
plants may sometimes reduce populations of certain soil-dwelling plant-parasitic nematodes by producing chemicals that kill or repel nematodes, stimulate premature egg hatch, suppress nematode growth, or
disrupt the attraction between nematodes seeking to mate. However, crops suppressive to one species of
nematode often host other nematode species. Rotating specific marigold cultivars with crops such as lilies
grown for bulb production has been somewhat successful in controlling certain nematodes. The marigolds must be left in the soil, either through cultivation or by mowing the tops and leaving the roots underground. However, this practice is generally not recommended because phytotoxicity to lilies and other
crops is commonly observed when they are grown in rotation after incorporating marigolds into the soil.
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Several biologically-based (microbial) nematicides are registered in California. Their efficacy for controlling root-knot nematodes has been studied in vegetable crops in Southern California. These field experiments found their effectiveness to be inconsistent at best.
Organically Acceptable Methods
Certain amendments and biological control products, anaerobic soil disinfestation, cultural practices, heat
pasteurization, hot water dips, sanitation, and solarization are organically acceptable management methods.
Fumigants
A soil fumigant can be used in certain situations to reduce nematode populations before planting. Before
using a fumigant, be sure that nematodes or other soil pests are the cause of your problem by having a
laboratory test performed or by having an expert examine your plants and soil. Consider alternatives before using a nematicide. Be sure the nematicide is registered for that crop or growing situation. Follow
label directions strictly; the improper application is not only illegal but often ineffective and may be hazardous. Fumigants such as 1,3-dichloropropene* and metam sodium* are a source of volatile organic
compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. (*Permit required from county agricultural commissioner for purchase or use.)
Fumigate only as a last resort when other management strategies have not been successful or are not
available. Soil fumigants may only be applied by a regulated, commercial applicator. Consult UC's Field
Fumigation: Pesticide Application Compendium, Vol. 9, the Department of Pesticide Regulation's Addendum
to the Field Fumigation Study Guide (PDF), and the office of the local county agricultural commissioner for
more information.
Common name
Amount to use
REI‡
PHI‡
(Example trade name)
(hours)
(days)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM
value listed first—the most effective and least harmful to the environment are at the top of the table. When
choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
Preplant
A.
1,3-DICHLOROPROPENE*§/CHLOROPICRIN*§
(InLine, Telone C-35)
Label rates
See label
NA
COMMENTS: Multipurpose liquid fumigant for the preplant treatment of soil to control plant-parasitic nematodes, symphylans, and certain soil-borne pathogens using drip irrigation systems only. Use of a tarp seal is
mandatory for all applications of this product.
B.
1,3-DICHLOROPROPENE*§
(Telone EC)
Label rates
5 days
NA
COMMENTS: Liquid fumigant for the preplant treatment of soil against plant-parasitic nematodes and certain other soil pests in cropland using drip irrigation systems only.
C.
CHLOROPICRIN*§
(Tri-Clor, Tri-Clor EC)
Label rates
See label
NA
D.
METAM SODIUM*§
(Vapam HL, Sectagon-42)
Label rates
See label
NA
COMMENTS: Contact your farm advisor for advice on the most effective application method for a particular
situation.
E.
METAM POTASSIUM*§
(K-PAM HL )
Label rates
See label
NA
COMMENTS: Contact your farm advisor for advice on the most effective application method for a particular
situation.
F.
ETHOPROP*§
(Mocap EC)
Label rates
COMMENTS: Apply just before planting. Make only one application per crop.
72
NA
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G.
1,3-DICHLOROPROPENE*§
(Telone II)
Label rates
5 days
NA
COMMENTS: Liquid fumigant for the preplant treatment of soil against plant-parasitic nematodes and certain other soil pests in cropland using drip irrigation systems only.
H.
DAZOMET
(Basamid G)
Label rates
See label
NA
COMMENTS: Granular fumigant for preplant treatment of soil or substrates against (some) plant-parasitic
nematodes.
I.
CHLORFENAPYR
(Pylon)
Label rates
12 hrs
NA
COMMENTS: Nematicide and Miticide only for greenhouse ornamentals and vegetables. For managing foliar nematodes (Aphelenchoides spp.) ONLY; not for control of other plant-parasitic nematodes.
‡
Restricted entry interval (REI) is the number of hours or days from treatment until the treated area can be safely entered
without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the
REI exceeds the PHI. The longer of these two intervals is the minimum time that must elapse before harvest may occur.
*
Permit required from county agricultural commissioner for purchase or use.
§
Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements, which may be lower than maximum label rates.
NA
Not applicable.
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Weeds
(Section reviewed 7/20)
COMMON AND SCIENTIFIC NAMES OF WEEDS IN
FLORICULTURE AND NURSERIES (7/20)
Weeds are broadly divided into broadleaf plants (dicotyledons) or narrowleaf plants (monocotyledons).
Most narrowleaf plants are grasses, but this group also includes sedges, such as yellow nutsedge, which
are important weeds. Another way to classify weeds is by when they germinate and grow. Many common weed species are winter annuals, germinating mainly in fall, growing through winter and spring,
and dying as summer approaches. Summer annuals germinate in spring, grow through summer and die
as the temperature drops in the fall. Irrigation can alter the germination time of weeds and prolong the
life span of some annuals and delay their senescence. A few weeds complete a life cycle in 2 years and are
referred to as biennials (e.g., bristly oxtongue). Some of the worst weed species are perennials; weeds that
live for 2 years or more. These include bermudagrass, creeping woodsorrel, and nutsedge that persist
through their vegetative propagules (stolons, rhizomes, or tubers). See the Common Weeds in Floriculture and Ornamental Nurseries table for a list of these and links to photographs and more information on
them.
Common Weeds in Floriculture and Ornamental Nurseries.
COMMON NAME
WINTER ANNUALS
bittercress
bluegrass, annual
burclover, California
chickweed, common
cudweeds
filarees
goosefoot, nettleleaf
groundsel, common
lettuce, prickly
mallow, little (cheeseweed)
mustard, wild
nettles
pearlwort
radish, wild
rocket, London
shepherd's-purse
sowthistle, annual
spurry, corn
SCIENTIFIC NAME‡
Cardamine spp.
Poa annua
Medicago polymorpha
Stellaria media
Gnaphalium spp.
Erodium spp.
Chenopodium murale
Senecio vulgaris
Lactuca serriola
Malva parviflora
Brassica sp.
Urtica spp.
Sagina sp.
Raphanus raphanistrum
Sisymbrium irio
Capsella bursa-pastoris
Sonchus oleraceus
Spergula arvensis
Continued on next page . . .
Weeds
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Common Weeds in Floriculture and Ornamental Nurseries, continued
COMMON NAME
SCIENTIFIC NAME‡
SUMMER ANNUALS
barnyardgrass
Echinochloa crus-galli
buttercup, yellow
Ranunculus sp.
crabgrasses
Digitaria spp.
fleabane, hairy
Conyza bonariensis
henbit
Lamium amplexicaule
horseweed
Conyza canadensis
junglerice
Echinochloa colona
lambsquarters, common
Chenopodium album
nightshade, black
Solanum nigrum
nightshade, hairy
Solanum physalifolium
pigweed, prostrate
Amaranthus blitoides
pigweed, rough
Amaranthus retroflexus
pigweed, tumble
Amaranthus albus
puncturevine
Tribulus terrestris
purslane, common
Portulaca oleracea
sprangletops
Leptochloa spp.
spurges; prostrate, creeping, or
Euphorbia (=Chamaesyce) spp.
spotted
willowherbs
Epilobium spp.
COMMON BIENNIALS AND PERENNIALS
bermudagrass
Cynodon dactylon
bindweed, field
Convolvulus arvensis
johnsongrass
Sorghum halepense
kyllinga, green
Kyllinga brevifolia
nutsedge, purple
Cyperus rotundus
nutsedge, yellow
Cyperus esculentus
oxtongue, bristly (biennial)
Picris echioides
woodsorrel, creeping
Oxalis corniculata
MISCELLANEOUS
liverwort
Marchantia polymorpha
mosses
Bryophytes (a division taxon)
‡ Scientific names are genus and specific epithet except where noted.
Growing site and production practices largely determine which weeds are likely to become problems at a
site. For example, weeds commonly associated with container nursery production include creeping
woodsorrel, common groundsel, lesser-seeded bittercress, northern willowherb, and prostrate and spotted spurge. Sometimes annual bluegrass, liverwort, or pearlwort are a problem. In greenhouses, weeds
that thrive in moist conditions often proliferate. These include liverwort, mosses, and pearlwort. In field
sites, weed species vary greatly but the weed spectrum can be influenced by management practices in the
field and by the environment. Because of these variations, each type of production situation is addressed
separately in this guideline. After the section on general methods of weed management, there are special
sections for weed management in
•
container nurseries
•
field-grown trees and shrubs
•
field-grown flowers
•
greenhouse-grown crops
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GENERAL METHODS OF WEED MANAGEMENT (7/20)
Managing weeds in ornamental plant production, whether in field soil, greenhouses, or outdoor containers,
can be difficult but is essential to successful production. Weeds not only compete with the crop for plant
nutrients and sunlight but are also unsightly and do not meet clean nursery quality standards. In addition,
ornamental plants infested with certain noxious weeds cannot be sold because of quarantine regulations.
Because of the high value of ornamental crops and the limited number of herbicides available, growers often resort to costly hand-weeding. However, many of the strategies used in vegetable row crops or tree
crops can be adapted for use in field-grown trees and cut flower production. For example, planting in rows
allows the field to be more easily cultivated by hand or mechanically. The use of drip irrigation in tree or
shrub production greatly reduces excessively wet areas, thus reducing the germination and growth of
weeds.
Whether ornamentals are grown in containers, fields, or greenhouses, there are some control practices
common to many methods of production that can reduce the impact of weeds on the crop as listed below
in no particular order.
Prevention
The most important factor in overall weed control is to prevent weeds from developing seed and perpetuating the weed problem. Sources of weed introduction include weedy stock, weed seeds in the growing
area or nearby, or plant propagules in manure, soil, uncomposted yardwaste, or other organic matter
sources. Many growers cultivate or treat the margins of the property with herbicides to reduce the number of windborne or water-carried seeds that can move to the growing area. Screens on open-water inflow sources can be installed to keep out water-borne seeds. When using fine-mesh screens, increasing
the surface area of the water intake and periodic debris removal may be needed to avoid clogging of the
water flow.
Cultivation
Weed management systems for field-grown ornamentals start with mechanical cultivation. Begin this
process by irrigating the field to induce weeds to germinate and then cultivate the new seedlings. Alternatively, the field can be sprayed with a postemergence herbicide after weed emergence so that the soil
will not be disturbed by cultivation before planting. Each time cultivation occurs, new weed seeds can be
brought close to the soil surface and germinate. This method reduces the soil seed bank so fewer weed
seeds will be present to germinate when the crop is planted.
After planting (and crop emergence if a seeded crop), preemergence herbicides can be used before weed
emergence or the field can be cultivated between rows after new weeds germinate or both. After harvest,
cultivate again to kill emerged weeds so they do not seed and replenish the weed seed bank.
Cover Crops
Cover crops can be used between rows and at field edges to improve weed management and to allow for
another crop to grow instead of weeds. See the Potential Cover Crops for Field-Grown Ornamentals for
the desirability of species for cover crops. The cover crop selected will depend on soil type, environmental conditions, and the ornamental crop. The cover crop can be a living mulch that is repeatedly mowed
to minimize competition, or it can be sprayed with herbicides and used as a nonliving mulch. Certain
cover crops can be hard to suppress with herbicides, such as white or strawberry clovers. An annual
cover crop can be established and allowed to senesce naturally or (where freezing temperatures occur) be
killed back by exposure to frost.
Weeds
Potential Cover Crops for Field-Grown Ornamentals.
DESIRABLE
INTERMEDIATE
LESS DESIRABLE
WINTER ANNUALS
beans, bell or fava
clover, rose or crimson
mustard,1 wild or black
bromegrass, blando
fescue, zorro
ryegrass, annual
pea, Austrian winter field
brome, California
rye, cereal
oat (forage)
vetch, hairy or purple
SUMMER ANNUALS
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beans, dry
sorghum
sudangrass
sudangrass/sorghum hybrids
PERENNIALS
perennial ryegrass/hard fescue
orchardgrass, berber
bermudagrass
clover, strawberry or white
1
Mustards can be undesirable cover crops because they can be invasive weeds in wildlands.
Mowing
Mowing is used to prevent rampant growth of the weeds, reduce the formation of seed, and reduce the
spread of weed seed into cultivated areas. Properly timed mowing can also suppress some perennial
weeds such as established johnsongrass. However, repeated mowing over a period of time (seasons or
years) without any other means of weed control tends to favor the establishment of low-growing perennial grasses, which are very competitive for water and nutrients. Also, species that have flower heads below the level of the blade are not effectively controlled. If performed after seed set, mowing can spread
weed seed and exacerbate weed problems.
Flaming
Flaming can be used before planting or on weeds between crop rows. To avoid injuring the crop, direct
the flame at young weeds between the rows or use shields. Broadleaf weeds are controlled more effectively than grasses by flaming, and young weeds are better controlled than older ones. Because of the cost
of fuel, the time required to pass over the beds, potential injury to workers, and fire hazard, flaming is not
a widely used method of weed control for field-grown flowers or nurseries.
Hand-removal
Hand-hoeing or hand-pulling of weeds is always a part of crop management because cultivation does not
remove all of the weeds. In some crops there may not be any other method of control. By removing the
few remaining weeds in the crop, not only will there be less competition, but fewer weed seeds will be
produced.
Mulches
Various kinds of bark, composted yardwaste, and other organic material can be used to help suppress
annual weeds by covering the soil surface and preventing weed seed germination and establishment.
Only 2 to 3 inches of fine organic mulch (finished yardwaste) may be required to totally eliminate light on
the soil and suppress the growth of weeds. An advantage of the fine mulches is that after the crop is harvested, the mulch can be worked into the soil to improve drainage, soil structure, and water-holding capacity of the soil. A disadvantage of fine mulch is that weed seeds that fall on it will germinate and grow.
Coarse wood chips or bark may require 3 to 6 inches of material to eliminate light. Synthetic materials
(geotextiles, landscape fabrics) made of polypropylene or polyester can also be used as mulches but because of cost, they generally are used only with perennial shrubs or trees or under containers. Because
they last several years, they can be left on for the life of the tree or shrub, or they can be removed and reused. Dark plastic mulches can be used for weed control when using drip or furrow irrigation.
Soil Solarization
Heating soil to high temperatures can kill many weed seeds. Solarization is done by covering bare, moist
soil with clear plastic during periods of high solar radiation and temperature. In California's interior valleys, this is generally during June to August. Before placing the plastic on the site to be treated, cultivate
or closely mow any established plants and remove the clippings, then smooth the soil surface and irrigate
the area well. Place clear polyethylene that is ultraviolet (UV) resistant over the area and extend it about 2
feet beyond the infested area on all sides and pull it tightly so it is close to the soil. The plastic must be left
in place and maintained intact for 4 to 6 weeks for control of weeds. Many annual weeds can be controlled using this method. Weeds not well controlled include clovers, field bindweed, and purple and yellow nutsedge.
Media for containers or for use in greenhouses can be solarized using clear bags or flats or small, low
mounds of soil covered with clear polyethylene. In greenhouses, beds can be solarized before planting.
See Soil Solarization: A Nonpesticidal Method for Controlling Diseases, Nematodes, and Weeds, UC ANR
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
Publication 21377 and UC IPM Pest Notes: Soil Solarization for Gardens and Landscapes, UC ANR Publication
74145, for more details.
Transplants
Using transplants rather than direct-seeding a crop allows the crop to establish more quickly and be more
competitive with weeds. Also, a transplant is generally more tolerant to soil-applied (preemergence)
herbicides than are germinating crop seeds.
Herbicides
Herbicides are used in many ornamental production areas as an economical option to control weeds. By
using herbicides before weeds emerge, weed competition with the ornamental crop can be reduced or
eliminated, resulting in higher quality ornamental plants and less labor costs.
Herbicides are generally classified according to when they are used in relation to crop and weed growth
stage. Preplant herbicides are applied before planting. These herbicides are used before the desirable
plants are present because some can control both germinating seedlings and established plants.
Preemergence herbicides kill weeds at the seed germination stage. These herbicides are applied before
weeds emerge. Postemergence herbicides are applied after the weeds have emerged. Preemergence and
postemergence herbicides may be applied before or after the crop is planted depending on the crop and
the herbicide selected. See the section SUSCEPTIBILITY OF WEEDS TO HERBICIDE CONTROL to guide
herbicide choice based on the weed species present.
Preplant herbicides
Herbicides that are applied before planting the crop may be fumigants, nonselective or selective
postemergence herbicides, or preemergence herbicides, which are selective because they are generally
safe for use around established plants. The fumigant herbicides, such as metam potassium* and metam
sodium*, are often applied as an injection to cultivated soil. They are generally covered with a polyethylene tarp to seal in moisture and slow the escape of fumigant gas. Dazomet is a powder that is incorporated into the soil. All of these materials must be applied by licensed applicators. Nonselective postemergence herbicides can be used preplant as well. Certain preemergence herbicides can be applied and incorporated mechanically into soil before direct seeding or transplanting if the crop is tolerant to that herbicide. (*Requires a permit from the county agricultural commissioner for purchase or use.)
Preemergence herbicides
Preemergence herbicides must be applied before the weed seeds germinate. These herbicides comprise
the largest number of herbicides available to ornamental growers because they are generally safest for the
crop and the weed seedling stage is the easiest part of the plant cycle to interrupt. Examples of these herbicides are dimethphenamid-d, flumioxazin, indaziflam, isoxaben, napropamide, oryzalin, oxadiazon, oxyfluorfen, pendimethalin, prodiamine, and trifluralin. There are a number of preemergence herbicides
sold as combinations such as dimethenamid-p/pendimethalin (Freehand), oryzalin/isoxaben (Snapshot),
oxyfluorfen/oryzalin (Rout), and oxyfluorfen/pendimethalin (OH2).
Apply preemergence herbicides to the soil after cultivating or hand-weeding to remove emerged weeds.
Follow the application with an irrigation or rain to move the herbicide in the top 1/2 inch of media or soil
where the seeds are germinating. A second handweeding 7 to 10 days after an herbicide application may
be needed to ensure elimination of previously germinated seedlings. However, read the label to learn if
doing so will affect the chemical barrier. For example, oxadiazon and oxyfluorfen are taken up by the
seedling as it emerges; disturbing the soil may create some gaps in the herbicide barrier.
Because of the varied germination periods of the weed species and the selectivity and sometimes limited
persistence of the herbicides, it can be necessary to use different preemergence herbicides at different
times of the year or repeat application of a particular herbicide to achieve the best control. For example,
common groundsel and lesser-seeded bittercress can germinate at almost any time during the year, but
their maximum germination in a field situation occurs in a cool, moist environment. Thus, a late summer
herbicide treatment for control of winter annual seedlings is most desirable. For summer weeds such as
crabgrass and purslane, apply herbicides in late winter. Keep in mind that where artificial conditions for
germination can occur, such as in a container nursery where irrigation may occur daily, these weeds can
germinate at any time. The length of time a preemergence herbicide stays active is also an important
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consideration in application frequency and timing. For example, because of frequent irrigation herbicides
may not control weeds for as long as stated on the label.
Postemergence herbicide
Postemergence herbicides are applied after weeds have emerged. Some are very selective and control
only a narrow range of weed species. Examples of selective postemergence herbicides include clethodim,
fluazifop-p-butyl, and sethoxydim. Fluazifop-p-butyl and sethoxydim control most annual grasses, except annual bluegrass and fine fescue. Clethodim will control annual bluegrass as well as other grasses.
Products containing phenoxy herbicides, such as 2,4-D, will selectively control broadleaf weeds in monocots but will injure a broadleaf crop. There are no selective postemergence herbicides that can be used
over a wide spectrum of ornamental species for broadleaf weed control. Nonselective herbicides are those
containing diquat, glufosinate, glyphosate, pelargonic acid, and plant oils such as eugenol. Nonselective
herbicides can be used around the field to keep weeds from seeding but must be kept away from the
crop.
Apply postemergence contact herbicides when weeds are in the seedling stage, the stage when they are
the most susceptible and require the least amount of herbicide for effective control. Translocated herbicides such as glyphosate and the grass selective herbicides can be effective on bigger weeds. In some
field-grown flowers, shrubs, or trees, control of grasses with the postemergence herbicides clethodim,
fluazifop-p-butyl, or sethoxydim can be very effective. Many postemergence herbicides need addition of
an adjuvant (surfactant oil) for maximum control. Check the herbicide label for information about
whether a surfactant should be added and which type of surfactant to use and the rate.
By using preemergence or postemergence herbicides or, where possible, mulches instead of cultivation or
hand-weeding, the root system of desirable plants is not disturbed. Roots are not cut off with a hoe or
crop plants pulled accidentally. And because new weed seeds are not brought to the soil surface, as they
would be with cultivation, fewer weeds will germinate to start a new weed crop.
Application of Herbicides
Calibration of the equipment is essential for proper application regardless of whether the herbicide is
sprayed or applied dry as granules. Granules and wettable powder formulations can cause severe wear to
the application equipment, so the equipment will need to be calibrated more frequently.
Most liquid herbicides are applied at 20 to 60 gallons of solution per acre at pressures of 30 to 40 pounds
per square inch (psi). Applying liquids with a single nozzle hand wand does not give as uniform distribution as multiple nozzles on a boom. Because the effectiveness of preemergence herbicide applications is
highly dependent on even soil coverage, make applications as uniformly as possible. When applying to
container plants be aware that the media surface may be blocked by plant foliage.
Where the crop makes it difficult for the herbicide to reach the media, a granular can be more effective.
Granules are applied to dry foliage and if the foliage restricts the movement to the media surface, the foliage can be lightly brushed or shaken with a broomstick or similar tool to dislodge granules. Recalibration
of the application equipment is important when changing herbicides as granule size and weight differ
among herbicides.
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SUSCEPTIBILITY OF WEEDS TO HERBICIDE CONTROL (7/20)
Mode of Action
ANNUAL WEEDS
barnyardgrass
bittercress, lesserseeded
bluegrass, annual
burclover, California
chickweed, common
crabgrasses
cudweeds
filarees
fleabane
goosefoot, nettleleaf
groundsel, common
henbit
horseweed
junglerice
lambsquarters, common
lettuce, prickly
mallow, little
(cheeseweed)
mustard
nettle, stinging
nightshade, black
nightshade, hairy
pearlwort
pigweeds
purslane, common
radish, wild
rocket, London
shepherd's-purse
sowthistle, common
sprangletops
spurge, prostrate or
spotted
spurry, corn
willowherbs
BIENNIAL WEEDS
oxtongue, bristly
PERENNIAL
WEEDS
bermudagrass
(plant)
bermudagrass
(seedling)
bindweed, field
(plant)
bindweed, field
(seedling)
buttercup, yellow
johnsongrass (plant)
johnsongrass (seedling)
nutsedge, yellow
nutsedge, purple
woodsorrel, creeping
(plant)
Weeds
PREEMERGENCE
DIH DIM D/P FLM IND ISO I/T MCH NAP ORY O/O OXA OXY O/P PEN PRD TRI
14
15 15/3 14
29
21 21/3 15
15
3
3/14 14
14 14/3
3
3
3
C
—
C
—
C
—
C
—
C
—
N
C
C
C
C
P
C
P
C
P
C
C
C
C
P
C
C
C
C
P
C
P
C
P
—
—
P
P
C
—
C
C
C
—
C
—
C
C
—
C
C
—
—
—
—
—
—
—
—
C
C
—
C
C
—
—
—
C
—
C
—
C
C
—
—
C
P
—
C
C
—
C
C
C
—
C
C
C
—
C
C
C
C
C
P
C
C
—
C
N
C
C
N
C
C
P
C
C
C
P
N
C
C
C
C
C
C
C
P
C
C
C
P
C
C
C
N
C
C
N
N
N
P
N
N
N
C
P
C
N
C
C
P
C
N
C
C
N
P
C
C
C
N
C
C
N
P
N
C
P
C
N
C
C
C
C
C
C
C
C
P
C
C
C
P
C
C
C
N
N
C
C
C
P
C
P
C
P
C
C
P
C
P
N
C
C
P
C
C
C
P
P
C
C
C
C
C
C
C
P
C
C
C
P
C
C
C
N
C
C
N
N
N
C
N
C
N
C
C
C
N
C
C
N
N
N
C
N
C
N
C
C
C
N
C
C
N
N
N
C
N
C
N
C
C
C
—
—
—
—
P
—
C
P
C
C
C
C
C
N
N
C
P
P
P
C
C
P
C
C
C
C
C
N
P
N
P
N
P
—
C
C
C
—
P
C
—
—
—
C
—
C
—
C
P
P
—
C
C
—
—
—
—
—
—
—
C
P
P
C
C
C
—
—
—
—
C
C
C
C
C
C
—
—
C
—
—
C
C
—
—
C
C
C
C
—
C
C
C
C
C
C
—
C
C
C
C
C
C
C
C
C
C
C
C
N
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
C
C
C
P
C
C
N
N
P
P
C
N
P
P
N
N
C
C
C
N
C
P
C
C
N
N
P
N
N
C
C
C
N
N
N
N
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
C
C
C
C
C
C
P
C
C
C
C
C
P
C
C
C
C
C
C
N
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
P
N
N
C
C
C
N
N
N
N
C
C
N
P
N
N
C
C
C
N
N
N
N
C
C
N
P
N
N
C
C
C
N
N
N
N
C
C
—
—
—
—
C
—
—
C
—
C
C
P
C
P
C
N
C
N
C
P
C
C
N
P
P
C
C
C
C
N
C
N
C
N
—
—
—
—
—
N
N
N
N
N
N
N
N
N
N
N
N
N
—
—
—
N
N
N
N
N
N
N
N
N
N
N
N
N
C
—
C
—
—
N
C
C
C
C
C
P
N
N
C
C
C
P
N
N
—
N
N
N
N
N
N
N
P
N
N
N
N
N
C
—
P
—
—
N
C
N
N
P
C
C
C
C
P
P
C
—
N
C
P
—
C
P
—
C
—
—
—
—
N
—
N
N
N
N
N
C
N
N
C
N
N
C
N
N
C
N
N
N
N
N
N
N
N
N
N
N
P
N
N
P
N
N
C
N
N
C
P
—
—
P
—
—
P
—
—
P
N
—
N
N
—
N
N
N
N
N
N
P
P
N
P
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Susceptibility of Weeds to Herbicide Control (7/20)
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woodsorrel, creeping
(seedling)
MISCELLANEOUS
liverwort
C = control
—
—
C
—
C
C
C
—
—
—
C
—
—
DIH DIM D/P FLM IND ISO
P = partial control
DIH
DIM
D/P
FLM
= dichlobenil (Casoron)
= dimethenamid-P (Tower)
= dimethenamid/pendimethalin
= flumioxazin (Broadstar, Sureguard)
IND = indaziflam (Marengo G)
ISO = isoxaben (Gallery)
I/T
= isoxaben/trifluralin
MCH = metolachlor (Pennant)
N = no control
—
I/T
N
N
C
C
C
C
C
C
C
—
—
—
P
P
P
P
—
—
—
MCH NAP ORY O/O OXA OXY O/P PEN PRD TRI
— = Information not available or not presented
NAP
ORY
O/O
OXA
= napropamide (Devrinol)
= oryzalin (Surflan)
= oryzalin/oxyfluorfen
= oxadiazon (Ronstar)
OXY
O/P
PEN
PRD
TRI
= oxyfluorfen (Goal)
= oxyfluorfen/pendimethalin
= pendimethalin (Pre-M, Pendulum)
= prodiamine (Barricade)
= trifluralin (Treflan)
Susceptibility of Weeds to Herbicide Control, continued
Mode of Action
ANNUAL WEEDS
barnyardgrass
bittercress, lesser-seeded
bluegrass, annual
burclover, California
chickweed, common
crabgrasses
cudweeds
filarees
fleabane
goosefoot, nettleleaf
groundsel, common
henbit
horseweed
junglerice
lambsquarters, common
lettuce, prickly
mallow, little (cheeseweed)
mustard
nettle, stinging
nightshade, black
nightshade, hairy
pearlwort
pigweeds
purslane, common
radish, wild
rocket, London
shepherd's-purse
sowthistle, common
sprangletops
spurge, prostrate or spotted
spurry, corn
willowherbs
BIENNIAL WEEDS
oxtongue, bristly
PERENNIAL WEEDS
bermudagrass (plant)
bermudagrass (seedling)
bindweed, field (plant)
bindweed, field (seedling)
Weeds
C
POSTEMERGENCE
FLU GLU GLY PAR
1
10
9
22
CLE
1
DIQ
22
C
N
C
N
N
C
N
N
N
N
N
N
N
C
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
C
P
C
P
C
P
P
N
N
N
N
N
N
P
P
N
N
P
P
P
P
N
P
C
C
N
P
P
N
C
P
P
C
N
N
N
N
C
N
N
N
N
N
N
N
C
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
P
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
P
C
C
C
C
C
C
C
C
P
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
N
N
N
P
C
C
C
N
N
N
C
N
C
P
C
N
N
PEL
26
SET
1
P
—
C
P
C
C
N
P
P
C
C
C
C
P
P
P
N
C
P
C
C
—
C
N
P
C
C
C
P
C
—
P
C
P
C
P
C
P
P
N
N
N
N
N
N
P
P
N
N
P
P
P
P
N
P
C
C
N
P
P
N
C
P
P
C
N
N
N
N
C
N
N
N
N
N
N
N
C
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
—
N
N
P
C
P
N
P
C
C
C
C
C
P
P
P
N
N
C
C
C
P
N
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buttercup, yellow
johnsongrass (plant)
johnsongrass (seedling)
nutsedge, yellow
nutsedge, purple
woodsorrel, creeping (plant)
woodsorrel, creeping (seedling)
C = control
P = partial control
CLE = clethodim (Envoy)
DIQ = diquat (Reward)
FLU = fluazifop-p-butyl (Fusilade)
GLU = glufosinate (Finale)
Weeds
N
C
C
N
N
N
N
CLE
N
N
C
N
N
N
C
DIQ
N = no control
N
P
C
N
N
N
N
FLU
P
P
C
N
N
P
C
GLU
C
C
C
P
P
C
C
GLY
—
N
C
P
P
—
—
PAR
N
N
C
N
N
N
C
PEL
N
P
C
N
N
N
N
SET
— = Information not available or not presented
GLY = glyphosate (Roundup Pro)
PAR = paraquat (Gramoxone)
PEL = pelargonic acid (Scythe)
SET = sethoxydim (Vantage)
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Container Nurseries
INTEGRATED WEED MANAGEMENT FOR CONTAINER
NURSERIES (7/20)
The growth and vigor of nursery stock can be reduced when weeds are allowed to grow in the container
for any length of time. Slow-growing crops that do not cover the surface of the media in the container
quickly are particularly vulnerable to weed infestations. Managing weeds in container nurseries involves
eliminating weeds and their seed and preventing the introduction of new weed seeds into the nursery.
Although growing medial is usually weed-free at planting, weed seeds can be blown in from other areas
or may be brought in with the liner (transplant). Frequently, preemergence herbicides are applied to the
surface of potting mix in containers of 1 gallon or larger to prevent the establishment of weed seeds.
Mulches may also be applied after canning or after weeding. After container plants are established,
preemergence herbicides are applied one or more times per year for weed management. Hand-pulling of
weeds that have escaped the herbicide treatments is necessary to prevent them from setting seed and
reestablishing a weed population.
Most weeds in a container nursery come from
• contaminated liners
• equipment
• irrigation water
• movement of soil
• plants growing between, in, or near pots
• potting mix, if it is stored uncovered where weed seed can blow in
• vehicles
• windborne seeds
Transplants produced in the nursery or purchased from others should be free of weeds and weed seed
and moved into larger, weed-free containers. Use preemergence herbicides in and between the containers
to reduce contamination or reinfestation, but take care so that herbicides are not carried off-site in water
runoff.
The most effective way to manage weeds is to start with a clean area and to keep it clean by creating a
weed-free, well-drained site for containers. Covering the nursery site with concrete, a geotextile (landscape fabric), or gravel helps control weeds under and between containers. Control perennial weeds before grading and installing irrigation equipment because they are nearly impossible to control after a
nursery is established.
Soil Mixture
Although potting mix is usually weed-free, it can become contaminated with weed seed if stored uncovered where seeds can blow in from neighboring areas. Fumigate, solarize, or steam sterilize any seed-contaminated soil mix. Check the soil mix periodically for weed seeds by placing samples of soil mix in a flat
or two. Keep the flats moist and check for weed germination for 1 to 2 weeks. If weeds grow, consider
fumigation or solarization of the soil mix.
For fumigation to be most effective, the soil mixture needs to be uniformly wet for 3 to 4 days before fumigation treatment so that the weed seeds absorb water and begin to germinate. If the mix is too dry or
too wet or there are large clods of soil, fumigation will not be uniform. Fumigation is most successful
when the soil is placed on a concrete pad or in a container and the fumigant or steam is introduced at several locations in the mix.
There are two main methods to fumigate a soil mix:
1. Steam fumigation. The steam is usually mixed with air and injected into a loose soil mix to heat the mix
to at least 140°F for 30 minutes. Length of time and temperature are critical if weed seeds are to be controlled. Cover the pile so that the entire pile, including the outer edges, reaches 140°F. A major problem of steam fumigation is that equipment, such as a boiler and blower, are required.
Weeds
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2. Chemical fumigation. Fumigation with pesticides such as dazomet (Basamid), metam potassium*, or
metam sodium* is sometimes used as a preplant treatment in potting mixes. For recommended fumigants, see MANAGEMENT OF ROOT-KNOT AND OTHER SOIL-DWELLING NEMATODES. Dazomet is a dry formulation that is mixed into the potting mix before wetting the pile. The pile is then
covered for about 2 weeks as the dazomet degrades into the active fumigant, methyl isothiocyanate.
The cover is removed and the soil allowed to air for 2 weeks before using the mix for potting. Metam
potassium and metam sodium are liquids that can be applied in water to the mix and then tarped for 2
weeks. Air out the soil for 2 weeks before planting the crop. Fumigants such as metam potassium and
metam sodium are sources of volatile organic compounds (VOCs) but are minimally reactive with
other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available. (*Requires a permit from the county agricultural
commissioner for purchase or use.)
Although less commonly used, soil solarization can also be used to control weeds in the potting mix before planting. See the discussion of soil solarization in GENERAL METHODS OF WEED
MANAGEMENT at the beginning of the weeds section.
Monitoring Container Nurseries
See the Common Weeds in Container-Production Nurseries table for links to photographs and more information on these species. Because many of these weeds can germinate year-round in the nursery, check
the containers regularly. Some weed species can flower and produce seed in only a month from the seedling stage, so monitoring followed by hand-weeding is needed at least monthly to remove any weeds that
were missed by herbicide treatments or from the last hand-weeding. It is essential to monitor for winter
annual weeds germinating in late summer and for summer annuals germinating in late winter.
Common Weeds in Container-Production Nurseries.
Common name
Scientific name
bittercress
Cardamine spp.
cudweed
Gnaphalium stramineum
groundsel, common
Senecio vulgaris
lettuce, prickly
Lactuca serriola
liverwort
Marchantia polymorpha
pearlwort, birdseye
Sagina procumbens
sowthistle, annual
Sonchus oleraceus
spurge, prostrate or spotted
Chamaesyce maculata
willowherbs
Epilobium spp.
woodsorrel, creeping
Oxalis corniculata
Identifying the weeds present in a given situation is an important factor in deciding which weed control
strategies to employ. Use the Weeds of California, UC ANR Publication 3488, and the UC IPM Weed Photo
Gallery to help identify weeds. University of California Cooperative Extension advisors or county agricultural commissioners, botanic gardens, or arboretum personnel can also help with weed identification.
Once the weed is identified, the herbicide labels and tables of SUSCEPTIBILITY OF WEEDS TO
HERBICIDE CONTROL will help you determine the best herbicide or combinations of herbicides to supplement a weed management program and provide optimum control of the weed species present.
Herbicides
Preemergence herbicides are used extensively in container-grown ornamentals, usually in conjunction
with handweeding to control any weeds that escape the chemical treatment. The herbicides used depend
on the weed species expected (see monitoring section), the time of year, the stage of the ornamental
plants, and the tolerance of the ornamental plants to the herbicides. The weed species present at a particular site must be properly identified in order to select the effective herbicide. Apply the herbicide as soon
as possible to achieve optimal weed control but keep in mind that some plants may be injured if applied
before the soil has settled around the roots.
Herbicides used in container production will not harm the ornamental species listed on the label if care is
taken to use them properly. A number of factors determine if the ornamental plant will be adversely affected. These include the
Weeds
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•
•
•
•
•
•
•
•
•
Degree of plant establishment. Newly-planted plants are more sensitive because generally they
have smaller root systems than established plants.
Dosage of the herbicide. Higher dosages can cause crop injury; rates above the label are illegal.
Use the lowest dose that will control the weeds targeted. Note that using too low of rate can promote the development of resistance to herbicide.
Formulation. Granular formulations are generally safer with some products than the emulsifiable
concentrate or wettable powder formulations. However, injury can result if the granules collect in
the whorl of the plant.
Plant size. The younger the crop plant the greater the sensitivity to herbicides, and therefore, the
greater the likelihood of it being injured.
Rate of plant growth. Actively growing plants often are more sensitive to injury from certain
herbicides than dormant plants.
Soil texture and organic matter content. These properties can affect an herbicide's tendency to
leach into the root zone. Some herbicides can be more strongly adsorbed on soil particles than
others. As clay and organic matter content increase, binding increases and usually there is less
leaching.
Spray techniques. The method of application will affect distribution of the herbicide on the target. For most herbicides, the height of the spray boom should be adjusted so that the top of the
ornamental plant receives uniform spray distribution. This means that with normal spray booms
equipped with fan type nozzles, the nozzles should be at least 20 to 24 inches above the top of the
plants. Spray booms adjusted too low can cause plant injury with certain herbicides. Individual
nozzles should be checked for proper flow rate and spray pattern.
Tank mixing of products. Mixing in wetting agents (chemicals that reduce the surface tension of liquids) or another herbicide that has wetting agents in it with an herbicide that has postemergence activity can greatly increase the activity and perhaps also increase crop injury and reduce selectivity.
Check the label and follow any instructions regarding adding adjuvants or tank-mixing products.
Temperature. Temperature affects rates of chemical reactions in plants. Higher temperatures can
greatly increase the speed of chemical reactions, which can result in greater injury to plants as
well as to weeds. Higher temperatures may also increase herbicide absorption through leaves
and roots.
Herbicide runoff can be a serious problem in some situations, so observe the following precautions to reduce runoff:
• Spot treat.
• Use herbicides with water solubility of less than 3.5 ppm as listed in the Herbicide Handbook and
certain online guides (PDF).
• Use low-volume applications. Use only as much water as needed to move the herbicide into soil
with the first irrigation following an application.
Container spacing can also affect herbicide loss when granular herbicides are applied. Tight spacing of
containers can keep 50% more of the herbicide in the container rather than on the ground compared to
containers that are spaced 8 inches apart. Additionally, herbicide loss can be reduced if drop spreaders
are used rather than rotary spreaders. However, herbicide that falls on the ground is not totally lost because it helps control weeds between containers and thus contributes to the total weed management.
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UC IPM Pest Management Guidelines - FLORICULTURE AND ORNAMENTAL NURSERIES
SPECIAL WEED PROBLEMS FOR CONTAINER NURSERIES (7/20)
BITTERCRESS (hairy bittercress, lesser-seeded bittercress, popweed)
Bittercress is a small winter annual that will germinate almost any time in container production. It grows
upright when the seed stalk starts to form and is easy to hand-weed at that stage, but as a seedling it is
very difficult to remove easily. It produces hundreds of seed per plant, and when the capsule matures it
expels the seed some distance from the original plant. Remove this weed before it flowers to reduce seed
production and new infestations. Herbicides that are effective against bittercress are those that contain
isoxaben, oxadiazon, or oxyfluorfen. Sanitation is also important to reduce the spread of this weed. Because
the seed of this weed adheres to soil on the outside of the pots, wash pots before reuse or moving them
from an infested area. The seeds are also easily carried in irrigation water. Avoid overwatering or allowing
water to runoff from an infested area to a clean one.
COMMON GROUNDSEL
Common groundsel is probably the most difficult weed to control in container nurseries in California. It is
a hardy weed that grows rapidly and germinates anytime during the year in container nurseries, whereas
in the field it usually germinates in fall and early winter. Preemergence herbicides suppress the rooting,
making the weed easier to pull. Also, because the seedling is smaller after the use of a preemergence herbicide, competition with the desirable plant is not very significant. Remove this weed before it flowers because its seeds are easily spread by wind. Preemergence herbicide combinations containing dichlobenil,
dimethenamid-P + pendimethalin, flumioxazin, isoxaben, napropamide, or oxyfluorfen have given good
control.
CREEPING WOODSORREL (Oxalis)
Creeping woodsorrel is a perennial plant that grows in a prostrate manner and forms roots along its stems
where nodes contact the soil. It is a prolific seed producer. When its seed pods mature, they burst open and
forcefully expel seeds, which may land several feet from the plant. Because the seeds are rough, they adhere to clothing or the surfaces of machinery and are easily dispersed. The primary method of managing
creeping woodsorrel is to hand-pull established plants before they set seed, being careful to remove as
much of the creeping stolons as possible, and to control germinating seeds with mulch or the preemergence
herbicides indaziflam, isoxaben, oryzalin, oxadiazon, oxyfluorfen, pendimethalin, prodiamine, or trifluralin.
CUDWEED
Cudweed is an annual that germinates in fall and grows through the winter and spring. It is a whitish,
hairy plant that has small inconspicuous flower heads. The preemergence herbicides dichlobenil, indaziflam, isoxaben, and oxyfluorfen have been effective in controlling the seedlings of this weed as they germinate.
LIVERWORT
Liverworts are nonvascular, primitive plants that reproduce vegetatively and through spores. Their flat
leaf-like structure is called a thallus and their root-like structure is a rhizoid. These plants can form dense
colonies in ornamental containers resulting in crop damage and reduced marketability. Preemergence
herbicides containing flumioxazin or oxyfluorfen provide limited control of this weed, but are not labeled
for use in greenhouses. There are no selective postemergence herbicides available.
PEARLWORT
Pearlwort is a low-growing winter annual that roots on the stems and forms mosslike mats in the container. It reproduces by seed. If oxadiazon has been used repeatedly without rotation to other herbicides it
becomes a dominant weed in the nursery. A preemergence application of isoxaben, napropamide, oryzalin,
pendimethalin, prodiamine, or trifluralin will control pearlwort.
SPURGE
Creeping and prostrate (spotted) spurge are low-growing annuals that grow rapidly and quickly produce
seed. They are more easily removed when older, but by then the seeds have usually been produced and fall
off the plant into the container when the weed is removed. Mulching reduces establishment. The
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preemergence herbicides dichlobenil, indaziflam, isoxaben, oryzalin, oxadiazon, oxyfluorfen, pendimethalin, prodiamine, and trifluralin will control spurge.
WILLOWHERB
There are at least two species of willowherb found in nursery containers, Epilobium paniculatum and E. ciliatum. Willowherb seeds profusely and the seed blows in the wind. Preemergence herbicides that have been
effective in controlling germinating seeds include dimethenamid-P + pendimethalin, flumioxazin, oxadiazon, and oxyfluorfen.
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HERBICIDE TREATMENT TABLE FOR CONTAINERS AND
FIELD-GROWN TREES AND SHRUBS (7/20)
Common name
(Example trade name)
Amount to use
REI‡
(hours)
PHI‡
(days)
Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider information relating to resistance management, the pesticide's properties, and application timing. Tank
mixes may be necessary to achieve desired control; see the table SUSCEPTIBILITY OF WEEDS TO HERBICIDE
CONTOL for information on control of specific weeds. Always read the label of the product being used.
Note: Not all ornamentals will tolerate each herbicide. Check the label for species selectivity.
PREEMERGENCE HERBICIDES
A.
DICHLOBENIL
(Casoron 4G)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: Not for container-grown ornamentals. Check label carefully for sensitive crops. A dormant
season application of dichlobenil can control many seed-propagated, perennial, broadleaf weeds and provide residual control through early summer. Good for control of Equisetum and mugwort.
B.
DIMETHENAMID-P
(Tower)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1:15
COMMENTS: Mix with isoxaben or pendimethalin to expand the weed spectrum controlled. Can be used
over the top on well-rooted plants. Check label for sensitive crops and test on a small group of each crop
before applying widely.
C.
DITHIOPYR
(Dimension 2EW)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: For application to established container and field-grown, tolerant ornamentals as listed on
the label.
D.
FLUMIOXAZIN
(Broadstar, granular)
See label
12
NA
(Sureguard, sprayable)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: Avoid contact with foliage of young crop plants. Wash foliage as soon as possible after application. Can cause stem dieback or leaf burn on sensitive plants. Has some postemergence activity. Provides
moderate liverwort control. Helps provide preemergence control of annual grasses, chickweed, hairy fleabane, horseweed, and other annual broadleaves. Test on a small number of plants before using widely.
E.
INDAZIFLAM
(Marengo G)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 29
COMMENTS: Not for use on certain field-grown trees and shrubs; check label for permitted uses. Long residual. Irrigate immediately following application for best activity. Can be used on many ornamentals and
also used around beds and greenhouses for long-term, preemergence, weed control.
F.
ISOXABEN
(Gallery SC)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 21
COMMENTS: Excellent herbicide for broadleaf weed control. Does not control annual grasses and willowherb, therefore often it is mixed with oryzalin or trifluralin to control grasses. It is safe on a wide range of
woody ornamentals.
G.
METOLACHLOR
(Pennant Magnum)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 15
COMMENTS: Controls yellow nutsedge as well as some annual grasses, but to be effective it must be incorporated into the soil where nutsedge germinates and grows through the treated area. Check label for crop
safety. This herbicide is one of the more soluble products (solubility 490 ppm) – make sure that it does not
move with irrigation or rainwater.
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H.
NAPROPAMIDE
(Devrinol DF-XT)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 15
COMMENTS: Needs mechanical incorporation (such as a power tiller, adequate irrigation, or 1 to 2 inches
of rainfall within 2 to 3 days) for optimum results. The first irrigation seems to be critical for maximum activity. Safe on many woody plants but is weak in controlling some broadleaf weeds such as members of the
aster and nightshade families, oxalis, and spurge. An excellent grass herbicide and can suppress common
groundsel. Generally less efficacious but often safer than the combination herbicides, it is useful in herbaceous crops. Unless it is applied before rooted liners are established, injury is rare. If placed in the container
around the newly planted liner before an irrigation settled the soil or if placed in the root zone, injury
(stunting) may result. If the soil is moist and there is no rainfall or irrigation within 7 days following application, an appreciable amount of the herbicide is lost and weed control will be lessened.
I.
ORYZALIN
(Surflan AS)
See label
See label
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: A relatively broad-spectrum preemergence herbicide that does not need mechanical incorporation. Controls germinating seeds of annual grasses and many broadleaf weeds and can be used safely
around many herbaceous and woody ornamentals. Leaches slightly into the soil from rainfall or irrigation.
Can cause girdling of certain gymnosperms at the soil line: young hemlocks or firs (Abies spp.) up to about
3 years of age are affected, but arborvitae, junipers, pines, and Taxus are more tolerant. Stems of Monterey
pines may exhibit some swelling. Oryzalin is a strong root inhibitor but most broadleaf ornamentals are
very tolerant to oryzalin if the herbicide is not in the root zone. Commonly used in combination with other
herbicides to widen the weed spectrum controlled.
J.
OXADIAZON
(Ronstar G)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: Not for use in conifer nurseries or on certain weeds species; see label. A broad-spectrum
preemergence shoot-girdling herbicide. In containers, granular oxadiazon plus napropamide is a good
combination with a broad range of safety in woody plants. The wettable powder formulation should not be
applied over young growth. Oxadiazon does not control weeds in the chickweed family but napropamide
controls those. Has a relatively long residual, 12–16 weeks. Oxadiazon is not very effective on certain
broadleaves including chickweed, horseweed, and pearlwort. Oxadiazon is very effective when applied in
fall or spring. Oxadiazon does not leach readily in the soil, is not a root inhibitor, and thus is less likely to
injure established species. Injury may occur if oxadiazon is applied to wet foliage, is not washed from the
foliage, or the granules collect in leaf bases or crowns. If treated soil is cultivated, weed control effectiveness is reduced.
K.
OXYFLUORFEN
(Goal 2XL)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: For use only around conifers and selected deciduous trees grown in the field. Excellent in
dormant or hardened conifers where groundsel, malva, mustards, or purslane are found. Controls these
weeds in a few days and provides residual, broadleaf control. Oxyfluorfen cannot be safely sprayed over
most deciduous plants. Safest to the conifers when applied as granules. Weak on common chickweed,
grasses, and horseweed. Oxyfluorfen acts by girdling the stem of seedlings; thus in soil, oxyfluorfen is most
effective with frequent irrigation. If treated soil is cultivated, weed control is reduced.
L.
PENDIMETHALIN
(Pendulum 2G, Pendulum AquaCap)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Do not apply Pendulum AquaCap over the top of transplants; see label. Gives excellent grass
control and controls many broadleaf weeds. Weed spectrum controlled is similar to that of oryzalin. Often
combined with an additional herbicide to widen spectrum of weeds controlled. Controls oxalis and spotted
spurge. An encapsulated formulation (AquaCap) has no odor and less persistent orange color. Though it is
a root inhibitor, it is less injurious to roots than oryzalin or prodiamine.
M.
PRODIAMINE
(Barricade)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER: 3.
COMMENTS: Stable on the soil surface. Does not provide as long of weed control as oryzalin at the maximum label rates for both. Has been less effective for groundsel and spurge suppression than some other
dinitroaniline herbicides. Inhibits root growth. Low water solubility and does not move deeply in the soil.
N.
TRIFLURALIN
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(Lebanon Treflan)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: In the same class of herbicides as oryzalin (dinitroanilines), but it is not as stable on the soil
surface. Must be incorporated with cultivation or irrigation or covered with a mulch very soon after application. Inhibits root growth. Often mixed with other herbicides (benefin or isoxaben) to widen the weed
spectrum controlled.
PREEMERGENCE COMBINATIONS
Note: For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum active ingredient (a.i.) on any label when tank mixing products that contain the
same a.i.
A.
DIMETHENAMID-P/PENDIMETHALIN
(FreeHand 1.75G)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 15/3
COMMENTS: Controls many common nursery weeds such as eclipta, oxalis, spurges, and willowherbs. Can be
applied very soon after potting. Provides preemergence control or suppression of yellow nutsedge.
B.
ISOXABEN/TRIFLURALIN
(Snapshot 2.5 TG)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 21/3
COMMENTS: Gives broad-spectrum control of annual broadleaf and grass weeds. Apply only to soil where established weeds have been removed. If the soil has been freshly cultivated, apply only after the soil has settled,
then follow with an irrigation.
C.
ORYZALIN/OXYFLUORFEN
(Rout)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 3/14
COMMENTS: Provides excellent broad-spectrum control of annual broadleaf and grass weeds. Can be applied
after a cultivation to reduce subsequent germination. Water in after application. If granules remain in plants at
the base of the leaf or in whorls, burn will occur. Residual control is 3–4 months.
D.
OXYFLUORFEN/PENDIMETHALIN
(OH2)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 14/3
COMMENTS: Provides excellent broad-spectrum control of annual broadleaf and grass weeds. Should be watered-in immediately after application. Slightly less root pruning than the oryzalin/oxyfluorfen formulation
(Rout). Residual control is about 3 months.
E.
OXYFLUORFEN
(Goal 2XL)
See label
24
NA
. . . PLUS . . .
OXADIAZON
(Ronstar Flo)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 14/14
COMMENTS: Not currently registered in California for use on annual bluegrass, annual sedge, bristly oxtongue,
cheeseweed, fiddleneck, fireweed, shepherd's-purse, sow thistle, ripgut bromegrass, and wild oats. Gives broadspectrum control of grasses and broadleaf weeds. Soil should be thoroughly settled after cultivation and rainfall
or irrigation because the products form a surface barrier that controls seedlings as they germinate and grow
through the herbicides. Cultivation after treatment destroys the control.
F.
PRODIAMINE/OXYFLUORFEN
(Biathlon)
See label
WSSA MODE-OF-ACTION GROUP NUMBERS1: 3/14
COMMENTS: See the comments above on these herbicides individually.
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See label
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Common name
(Example trade name)
Amount to use
REI‡
(hours)
PHI‡
(days)
Selective (broadleaves)
A.
OXYFLUORFEN
(Goal 2XL)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: For use only around conifers and selected deciduous trees grown in the field. Postemergence
applications of oxyfluorfen will control certain annual broadleaf weeds. Effective only on certain young
seedling weeds, especially little mallow. Perennial broadleaf weeds will be burned but not controlled. Activity is enhanced if a surfactant or crop oil is added. Spruces and true firs are injured by oxyfluorfen during their early flush but after about 5 weeks of new growth, they are tolerant. Dormant applications do not
cause injury.
Selective (grasses)
A.
B.
CLETHODIM
(Envoy Plus)
See label
WSSA MODE-OF-ACTION GROUP NUMBER1: 1
COMMENTS: Controls most annual grasses, including annual bluegrass.
24
NA
FLUAZIFOP-P-BUTYL
(Fusilade II)
See label
12
NA
(Ornamec Over-The-Top)
See label
4
See COMMENTS
WSSA MODE-OF-ACTION GROUP NUMBER1: NC
COMMENTS: Do not apply to ornamentals that may be harvested for food within 1 year after application.
Kills most annual and perennial grasses; however, it will not control annual bluegrass or hard fescue. Most
effective on young, actively growing grasses and less effective on mature grasses. Has injured certain
azalea cultivars, especially at high rates, causing spotting and necrosis on leaves. Certain junipers also are
sensitive to fluazifop-p-butyl; consult the label carefully.
Nonselective
A.
CAPRYLIC ACID/CAPRIC ACID
(Suppress)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: NC
COMMENTS: Works best on newly emerged weeds. Do not apply through any type of irrigation system.
B.
CITRIC ACID/CLOVE OIL
(BurnOut)
See label
WSSA MODE-OF-ACTION GROUP NUMBER1: NC
COMMENTS: Do not directly spray or allow to drift to desirable plants.
0
NA
C.
CLOVE OIL
(Matratec)
See label
0
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: NC
COMMENTS: For use in and around greenhouses. Do not directly spray or allow to drift to desirable
plants.
D.
DIQUAT
(Reward)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: Not for use in ornamental seed crops in California. Labeled for use around container-grown
ornamentals. Kills annual weeds, but only burns off the top of perennials. Contact activity only; affects
only green tissue. Good for weed control in winter.
E.
FATTY ACIDS/AMINE SALTS
(Finalsan Herbicidal Soap)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: NC
COMMENTS: For around field-grown ornamentals. Do not directly spray or allow to drift to desirable
plants.
F.
GLUFOSINATE
(Finale)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 10
COMMENTS: For use as a directed spray around container-grown ornamentals and established fieldgrown ornamentals. Do not apply directly to or allow to drift to desirable green tissue or thin or
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uncalloused bark. Contact herbicide with a limited amount of systemic activity; kills annual weeds, but
only burns off the tops of perennials.
G.
GLYPHOSATE
(Roundup Pro)
See label
4
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 9
COMMENTS: Labeled for use around container-grown ornamentals and established woody ornamentals.
A systemic herbicide that translocates to the roots and growing point of plants and kills the entire plant.
Effective on both annual and perennial weeds. Contact with leaves of the ornamentals will result in injury
to the plant. Glyphosate activity is increased in low water volumes. For example, greater activity is obtained at 20 gal/acre than at 50 gal/acre. This herbicide can be used alone or combined with a
preemergence herbicide.
H.
PARAQUAT*
(Gramoxone SL 2.0)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: For use as a directed around established field-grown ornamental trees. Do not apply directly to or allow to drift to desirable green tissue or bark. Kills annual weeds, but only burns tops off
perennials. Controls young annual weeds with contact activity only and affects only green tissue.
I.
PELARGONIC ACID
(Scythe)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 26
COMMENTS: Labeled for use around container-grown ornamentals. Works by contact activity only (does
not move in plants) and affects only green tissue. Good control of young annual weeds, but only burns
off the top of perennials. Must be applied at high rates in high volumes of water. Very rapid activity.
1
Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action.
Although weeds may exhibit multiple resistance across many groups, mode-of-action numbers are useful in planning
mixtures or rotations of herbicides with different modes of action. For more information, see http://www.hracglobal.com.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area
can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to
harvest. In some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse
before harvest.
Permit required from county agricultural commissioner for purchase or use.
Not applicable.
‡
*
NA
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Field-Grown Trees and Shrubs
INTEGRATED WEED MANAGEMENT FOR FIELD-GROWN
TREES AND SHRUBS (7/20)
Field-grown trees and shrubs are generally grown in rows to facilitate planting, weeding by hand or mechanical cultivation, and cultural operations such as grafting and pruning. Most weeds are controlled in
established plantings by cultivation and application of preemergence herbicides, but perennial weeds
need to be controlled before the crop is planted.
Crop Rotation
Sometimes the field is fumigated before planting. During the growing season, cultivation, herbicides, or
other control methods are used. After the crop is harvested (either bareroot in winter or potted in spring),
the field is planted to a cereal crop in fall (barley, oats, or wheat) and harvested the following spring.
Herbicides can be used in the cereal crop that will reduce weed problems in the next crop of trees and
shrubs.
Solarization
Soil solarization is a valuable tool to clean up a site before a fall planting (see "Solarization" under
GENERAL METHODS OF WEED MANAGMENT.
Cover Crops
Cover crops, especially winter annuals such as barley, oat, wheat, or combinations of these with rose clover, may be planted between tree rows in early fall. Cover crops reduce erosion and help maintain soil
organic matter when the cover is worked into the soil in the spring. Mow the cover crop and work it into
the soil before it seeds to reduce competition with the marketed crop.
Mulches
To reduce weeds in field rows, cuttings can be planted through holes in paper mulch. After planting, organic mulches (e.g., bark chips) can be applied around the plants and between the rows. Organic mulch
must be deep enough to shade out all weed seedlings as they germinate. Keep organic mulch back some
from basal stems of the crop to avoid promoting crown decay. Geotextile can be placed along the sides of
newly planted stock. The geotextile materials must be placed close to the plant to reduce the number
weeds will grow around the base of the plant. It is often beneficial to combine geotextile and organic
mulches to achieve good coverage and reduce ultraviolet degradation of the geotextile.
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SPECIAL WEED PROBLEMS FOR FIELD-GROWN TREES
AND SHRUBS (7/20)
LITTLE MALLOW (Cheeseweed)
Cheeseweed is a winter annual or biennial that forms hard seed that can remain dormant for long periods
of time. It generally germinates in fall after rainfall or an irrigation, but it may germinate any time during
winter and spring. The germinating seed is controlled by most preemergence herbicides, especially oxadiazon and oxyfluorfen. Flumioxazin, indaziflam, and isoxaben are also effective. Oxyfluorfen is also effective applied postemergence to the young plant. Glyphosate is not very effective against this weed.
YELLOW NUTSEDGE
Yellow nutsedge, sometimes call nutgrass, is a perennial sedge that is often confused with a grass. Fumigation before planting is usually effective in controlling this weed. Repeat applications of glyphosate (before the five-leaf stage when new tubers are formed) will reduce populations over time. Bentazon (Broadloom T&O) may be used around some tree species. If the area is left fallow, halosulfuron can be used and
then the crop can be planted the next season. Most preemergence herbicides do not control nutsedge, but
metolachlor (Pennant) will suppress sprouting of the tubers. Soil solarization will reduce yellow nutsedge
but will not eradicate it.
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HERBICIDE TREATMENT TABLE FOR CONTAINERS AND
FIELD-GROWN TREES AND SHRUBS (7/20)
See table in the previous section.
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Field-Grown Flowers
INTEGRATED WEED MANAGEMENT FOR FIELD-GROWN
FLOWERS (7/20)
Most weeds are controlled in field-grown flower crops with cultivation, hand-hoeing, preplant fumigation, and herbicides where there is crop safety. Crops are planted in rows to make cultivation easier and
to reduce crop damage from the cultivators. The crops may be direct seeded, but are often transplanted as
bulbs or plugs; transplants are more tolerant to handling and herbicides than direct-seeded crops. After
establishment, the crops can be cultivated two or three times before the crop canopy closes and the crop
begins to compete with the weeds. Some handweeding is usually required to remove all of the weeds.
Crop rotation is beneficial to reduce weeds in the crop. When the same crop is grown year after year, the
population of weed species that escape normal cultural practices increases. Good rotation crops are barley, oats, or wheat in winter and corn or sudangrass in summer.
Mulch
Unless the crop is sprinkler irrigated, a dust mulch often is created that keeps the soil surface dry and reduces the germination and establishment of annual weeds. Organic mulches used around transplants can
reduce weeds if the light cannot reach the soil. Fine mulches (composted yardwaste) applied 1-1/2 to 2
inches deep before the weed seeds germinate or when weeds are still in the seedling stage will control
most of the weeds. If the mulch is coarse, 3 to 6 inches may be required to completely eliminate light from
the soil, but unlike fine mulch, they do not allow weed seed germination in the mulch. Bulbs such as
Dutch iris may be good candidates for mulching for weed control. They have a large food reserve to push
through the mulch and may have better growth after mulching. With some crop species, having a fine
mulch right around the base of the plant may result in disease damage to plants. Mulches should not be
used if they contain weed seed or plant propagules (e.g., bulbs, rhizomes, or tubers).
Soil Solarization
Solarization effectively controls many weed species before planting. Solarization must be done during
periods of high solar radiation and temperature. Before placing the plastic on the site to be treated,
closely mow any established plants, remove the clippings, and then water the area well. Place clear polyethylene that is ultraviolet (UV) resistant over the area, extend it about 2 feet beyond the infested area on
all sides, and pull it tightly close to the soil. The plastic must be left in place and maintained intact for 4 to
6 weeks for control of weeds. Many annual weeds can be controlled using this method. Weeds not well
controlled include field bindweed, purple and yellow nutsedge, and sweet clover. In areas where solar
radiation and temperatures are low and marginal for solarization, purslane is not controlled well.
Flaming
Shielded propane burners effectively control young weeds between rows without disturbing the soil and
bringing weed seeds to the soil surface as cultivation would do. Flaming controls broadleaf weeds better
than grasses.
Herbicides
Most crops have one or more selective preemergence herbicides available for use. See the table
TREATMENT FOR FIELD-GROWN FLOWERS for selective herbicides that are registered on flower
crops. Postemergence herbicides (fluazifop-p-butyl, sethoxydim) can be used to control some grasses in
broadleaved crops. These are applied after the weeds emerge but while they are still small (1–3 inches in
height). If weeds are larger than 3 inches, more herbicide will be required and some weeds may not be
controlled. Broadleaf herbicides are generally not safe enough to use over flower crops. Even some selective grass herbicides may injure the crop if treated during the flowering stage. Control weeds when they
are small and before they flower and set seed. If a few weeds remain, hand weed them.
Herbicides can be used before the crop is planted. The broad-spectrum fumigants dazomet, metam potassium*, and metam sodium* can be used on prepared beds to control weeds and other soilborne pests. Depending on which fumigant is used, crops can be planted within days or in 2 to 4 weeks to allow time for
the fumigant to dissipate. (* Permit required from county agricultural commissioner.)
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Another method before planting is called a "stale seedbed" treatment. Beds are prepared for planting and
irrigated to germinate weeds. After most of the weeds have germinated, a postemergence herbicide like
diquat or glyphosate is applied to kill the weeds. Because no cultivation is done before planting, no new
weed seeds are brought to the surface. This "irrigate, germinate, eliminate" approach may be repeated
two or more times before planting the crop to reduce the seed populations in the soil.
Preemergence herbicides also can be applied after seeding or transplanting a crop but before the weeds
emerge. These herbicides generally must be incorporated mechanically along the planted row or leached
slightly into the soil by rainfall or 1/2 inch irrigation after application. See specific comments on the herbicides in the table TREATMENT FOR FIELD-GROWN FLOWERS.
After the annual flower crop has been harvested, clean up any weeds before they set seed. This can be
done most effectively by cultivating. If the field is not needed until the next season, it may be beneficial to
plant a cover crop to reduce weeds, keep the soil from eroding, reduce dust, and maintain organic matter
in the soil.
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HERBICIDE TREATMENT TABLE FOR FIELD-GROWN
FLOWERS (7/20)
Amount to use
Common name
(Example trade name)
REI‡
(hours)
PHI‡
(days)
Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider
information relating to environmental impact, resistance management, the pesticide's properties, and application
timing. Tank mixes may be necessary to achieve desired control; see the table SUSCEPTIBILITY OF WEEDS TO
HERBICIDE CONTROL for information on specific weed control. Always read the label of the product being used.
PREEMERGENCE HERBICIDES
A.
ISOXABEN
(Gallery 75DF)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 21
COMMENTS: Excellent herbicide for broadleaf weed control. Major weakness is annual grass control. Therefore, it is often mixed with oryzalin or trifluralin. Some broadleaf weed species can be controlled for up to 18
months with the labeled rates. Isoxaben does not effectively control Malvaceae (mallows). Some herbaceous ornamentals such as Digitalis, snapdragon, and Veronica may be killed by postplant, preemergence applications of
isoxaben.
B.
NAPROPAMIDE
(Devrinol DF-TX Ornamental)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 15
COMMENTS: Works best if mechanically incorporated or followed by rainfall or a sprinkler irrigation of 1/2
inch within 7 days after application. The first irrigation seems to be critical for maximum activity. It is an excellent grass herbicide and can suppress common groundsel. Generally less efficacious but often safer than the
combination herbicides. Is safer if applied after transplanting. If the soil is moist and there is no rainfall or irrigation within 7 days following application, an appreciable amount of the herbicide is lost and weed control will
be lessened.
C.
ORYZALIN
(Surflan AS Specialty)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: A relatively broad-spectrum preemergence herbicide. Can be applied up to 21 days prior to rainfall or before irrigation that is needed to move it into seed zone. Needs 1/2 inch of irrigation or rain to move it
to appropriate depth. Controls annual grasses and many broadleaf weeds and can be used safely on some crops
after transplanting. Leaches slightly into the soil with irrigation or rainfall. A strong root inhibitor. Many broadleaf ornamentals are tolerant to oryzalin if the herbicide is not in the root zone. Even when applied at rates of 4
lb a.i./acre, sometimes weeds in the aster family (common groundsel, fleabane, prickly lettuce, sowthistle),
mustard family (bittercress), and legume family (burclover) are not completely controlled. For most labeled
weeds, control usually is effective for 2–3 months. Oryzalin can control spotted oxalis and spurge from seed for
about 4 months. Tolerance is marginal on some crops; thus, use low rates until familiar with the herbicide and
crop combination.
D.
OXADIAZON
(Ronstar G)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 14
COMMENTS: A broad-spectrum preemergence herbicide that is used during the growing season from spring
until fall. It is moved off crop foliage and into the soil by a sprinkler irrigation following application. Oxadiazon
is a shoot-girdling herbicide. The granular formulation is safer than the wettable powder. It is weak on all of the
chickweed family and on certain broadleaves including chickweed, horseweed, and pearlwort. Has a relatively
long residual, 12–16 weeks, but if cultivated control will be lost. It is very effective when applied in fall or
spring. Does not leach readily in the soil, is not a root inhibitor, and thus is less likely to injure established species. Injury may occur if applied to wet foliage, if it is not washed from the foliage, or if the granules collect in
leaf bases or crowns.
E.
PENDIMETHALIN
(Pendulum 2G)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Gives excellent grass control and will control many broadleaf weeds. Controls a broad-spectrum
of broadleaf and grass weeds that is similar to what oryzalin controls. It is often combined with an additional
herbicide to widen the spectrum of weeds controlled. Though it is a root inhibitor, it is less injurious to roots
than oryzalin or prodiamine.
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F.
PRODIAMINE
(Barricade)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Prodiamine is stable on the soil surface. It also has been less effective for spurge and groundsel
suppression than some other dinitroaniline herbicides. Inhibits root growth.
G.
TRIFLURALIN
(Lebanon Treflan)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: In the same class of herbicides as oryzalin (dinitroanilines), but it is not as stable on the soil surface and must be incorporated with cultivation or irrigation. At low rates trifluralin has been used as a preplant
incorporated herbicide for some direct-seeded crops but is safer for use before transplanting.
PREEMERGENCE COMBINATIONS
Note: For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum active ingredient (a.i.) on any label when tank mixing products that contain
the same a.i.
A.
ORYZALIN/OXYFLUORFEN
(Rout)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBERS1: 3/14
COMMENTS: Limited registrations for field-grown flowers. Woody plants are more tolerant than herbaceous
plants. Provides excellent broad-spectrum control of annual broadleaf and grass weeds. If granules remain in
plants at the base of the leaf or in whorls, burn will occur. Residual control is 3–4 months.
POSTEMERGENCE HERBICIDES
Nonselective
A.
DIQUAT
(Reward)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: Labeled for use as a preplant treatment and directed postemergence use in field grown ornamentals. Kills annuals weeds, but only burns off the top of perennials. Controls young annual weeds with
contact activity only; affects only green tissue.
B.
GLYPHOSATE
(Roundup Pro)
See label
4
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 9
COMMENTS: Labeled for use before planting. A systemic herbicide that translocates to the roots and growing
point of the plants and kills the entire plant. Effective on both annual and perennial weeds. Contact with
leaves of the ornamentals will result in injury to the plant. Glyphosate activity is increased in low water volumes. For example, greater activity is obtained at 20 gal/acre than at 50 gal/acre. Can be used alone or combined with a preemergence herbicide. Often takes 7 or more days after application for complete control. Avoid
drift.
C.
PARAQUAT*
(Gramoxone SL 2.0)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: For harvest aid and desiccation applications, preplant or preemergence (broadcast or banded),
and postemergence directed spray. Controls young annual weeds with contact activity only; affects only green
tissue.
D.
PELARGONIC ACID
(Scythe)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 26
COMMENTS: Labeled for use preplant. Controls young annual weeds by contact activity only; affects only
green tissue. Must be applied at high rates in high volumes of water. Kills annual weeds, but only burns off
the top of perennials. Does not move in plant. Very rapid activity (minutes in high sunlight).
Selective (grasses)
A.
CLETHODIM
(Envoy Plus)
See label
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 1
COMMENTS: Controls most annual grasses, including annual bluegrass. Safe to use over most broadleaf ornamentals.
B.
FLUAZIFOP-P-BUTYL
(Fusilade II)
Weeds
See label
12
NA
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(Ornamec)
See label
4
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 1
COMMENTS: Postemergence contact selective herbicide for use in field grown ornamentals. Kills most annual
and perennial grasses, however it will not control annual bluegrass or hard fescue. It is most effective on
young actively growing grasses and less effective on mature grasses. Ornamec Over-The-Top not for use on
certain ornamental species in California; see label.
C.
SETHOXYDIM
(Poast)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 1
COMMENTS: Controls most annual grasses, except annual bluegrass or hard fescue. Most effective on young,
actively growing grasses. A nonphytotoxic oil or nonionic surfactant must be added for best control.
*
Permit required from county agricultural commissioner for purchase or use.
Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode-of-action numbers are useful in planning mixtures
or rotations of herbicides with different modes of action. For more information, see http://www.hracglobal.com.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered
without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds
the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
Not applicable.
1
‡
NA
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Greenhouse-Grown Crops
INTEGRATED WEED MANAGEMENT INSIDE
GREENHOUSES (7/20)
It is difficult to control weeds in greenhouses because the types of plants grown are generally sensitive to
herbicides and weeds are often hard to reach with an herbicide application. Only one preemergence herbicide is registered for use in greenhouses (indaziflam) and that is for beneath benches and greenhouse
floors only. Only a few weed species are common problems in greenhouses. They are all closely associated with high moisture and nutrients and spread rapidly if they are allowed to become established.
The most common weeds in and around greenhouses include annual bluegrass, common chickweed,
creeping woodsorrel, lesser-seeded bittercress, liverwort, moss, and pearlwort. Others that may be present include cheeseweed, cudweed, fireweed, prostrate and spotted spurge, sowthistle, and willowherb.
Controlling these weeds will also help reduce the reservoir of insects and plant pathogens that are often
associated with weeds.
Reducing standing water or high moisture around the interior perimeter of the greenhouse will help control these weeds as they often become established there and can spread from those habitats.
Cultural Control
Sanitation is the best method for weed control. Weeds may be brought into the greenhouse in potting mix
or with cuttings, bulbs, or other plant material or on dirty pots and tools. If weeds do get in, they should
never be allowed to flower and seed. This is especially true of bittercress and creeping woodsorrel (oxalis). Maintain trash cans in the greenhouse for weeds that are pulled during maintenance, so they can be
readily removed before flowering. Hand-weed frequently (daily or weekly) so no weeds go to seed. If the
floors are concrete, regularly wash or sweep away soil that drops to the floor so that weeds will not establish or seed. When crops are rotated, clean weeds out of the greenhouse and clean benches, tubing, and
walls to remove seeds that may be sticking to them. Irrigate with water that is free of fungal spores and
weed seeds.
If using raised or self-contained beds, pasteurize the soil before planting by either steaming or solarizing.
Solarization is described in GENERAL METHODS OF WEED MANAGEMENT and steam fumigation in
CONTAINER NURSERIES.
Herbicides
Only Marengo (indaziflam) is currently available for preemergence use in greenhouses and only under
benches or on the floor, not in the container. Many of the other preemergence herbicides are quite volatile at greenhouse temperatures and can move or accumulate or both in greenhouses to levels toxic to
crop plants. Even though some herbicides may be labeled for use in a crop, the label must specifically
state that it can be used in greenhouses to be legal and safe.
On the greenhouse floor and under the benches a postemergence herbicide can be used to reduce weed
populations and to keep the weeds from flowering and seeding. Provide good drainage and level the
gravel or soil under the benches to reduce water collecting in low areas. Wet areas increase the chance of
liverwort and moss infestations. Air movement at the floor level will help dry off the floor and will also
reduce the chance of infestations of weeds favored by wet areas. After a crop has been harvested, remove
any weeds to keep them from seeding so new seeds will not be added to the seedbank in soil.
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SPECIAL WEED PROBLEMS INSIDE GREENHOUSES (7/20)
LIVERWORT AND MOSSES
Liverwort and mosses can be found in many greenhouses where plants are highly irrigated and fertilized.
Their presence is exacerbated when there is high nitrogen in the upper soil surface, such as by top-dressing. These types of plants reproduce by spores and vegetatively and are easily spread throughout a
greenhouse. They can compete with the crop for nutrients and water and can also create a barrier on the
potting media surface that restricts water movement into the container resulting in poor irrigation efficiency and increased runoff. Decreasing the amount of water applied and avoiding top-dressing, as well
as inspecting plants before they come into the greenhouse, can reduce the presence and impact of liverwort and mosses.
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HERBICIDE TREATMENT TABLE FOR INSIDE
GREENHOUSES (7/20)
Common name
(Example trade name)
Amount to use
REI‡
(hours)
PHI‡
(days)
Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider
information relating to environmental impact, resistance management, the pesticide's properties, and application timing. Tank mixes may be necessary to achieve desired control; see the table SUSCEPTIBILITY OF WEEDS TO
HERBICIDE CONTOL for information on specific weed control. Always read the label of the product being used.
PREEMERGENCE HERBICIDES
A.
Indaziflam
(Marengo)
7.5-15.5 fl oz/acre
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 29
COMMENTS: Very long residual. For use under benches and greenhouse floors only. Do not exceed 18.5 fl oz
in a 12 month period.
POSTEMERGENCE HERBICIDES
A.
DIQUAT
(Reward)
Spot application: 1–2 qt plus 8–16 oz nonionic surfac24
NA
tant/100 gal water
Broadcast: 1–2 pt plus 16–32 oz nonionic surfactant/100
gal water
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: Apply in 15–40 gal water/acre. Do not allow contact of spray or drift to desirable foliage.
B.
GLUFOSINATE
(Finale)
Spot application: 1.5 fl oz/1 gal water
12
NA
Broadcast application: 3 qt when weeds less than 6
inches tall or 4 qt when weeds are 6 inches or taller
WSSA MODE-OF-ACTION GROUP NUMBER1: 10
COMMENTS: Apply as directed spray under benches or on floors of the greenhouse or around the periphery
of the greenhouse. Do not have air circulation fans running. Apply using large droplets and low pressure to
avoid drift or contact with green leaves or stems of crop. Do not use in greenhouses with edible crops.
C.
GLYPHOSATE
(Roundup Pro)
Spot application: 0.66–1.33 oz product/1 gal water
4
NA
Broadcast application: (annuals) 2 qt–1 gal/100 gal water
(perennials) up to 2 gal/100 gal water
WSSA MODE-OF-ACTION GROUP NUMBER1: 9
COMMENTS: Apply to young weeds under benches along walkways or along the edge of the greenhouses.
Use low pressure and large droplets to reduce chance of drift of spray on to leaves of the crop. Do not apply to
any runoff water. Turn off air circulation fans during application. Desirable vegetation should not be present
during application.
D.
PELARGONIC ACID
(Scythe)
See label
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 26
COMMENTS: Apply to young weeds under benches, along walkways, or along the edge of greenhouses.
1
Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode-of-action numbers are useful in planning mixtures
or rotations of herbicides with different modes of action. For more information, see http://www.hracglobal.com.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In
some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
Not applicable.
‡
NA
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INTEGRATED WEED MANAGEMENT OUTSIDE
GREENHOUSES (7/20)
Control weeds outside the greenhouse to help prevent movement of their seeds into the greenhouse.
Weed control in the area around the greenhouse will also reduce the chances that insects and plant pathogens that may live and reproduce on weeds will move into the greenhouse. If insects such as aphids, leafhoppers, lygus bugs, thrips, or whiteflies are abundant on the weeds outside the greenhouse, it may be
desirable to control them before the weeds are removed or these insects may move into the greenhouse
when the weed host dies.
Weeds outside the greenhouse can be controlled by cultivation or mowing where feasible and with herbicides. Take care when applying herbicide so that it does not move into the greenhouse by drift or runoff.
Preemergence herbicides can be used if the soil slopes away from the greenhouse so no soil or water that
may contain an herbicide gets into the greenhouse. Vents in the greenhouse and fans should be closed or
shut off while herbicide applications are being made so that the herbicide will not be drawn into the
greenhouse. Also, volatile herbicides (e.g., oxyfluorfen) should not be used around the outside of a greenhouse.
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HERBICIDE TREATMENT TABLE FOR OUTSIDE
GREENHOUSES (7/20)
Common name
(Example trade name)
Amount per Acre
REI‡
(hours)
PHI‡
(days)
Not all registered pesticides are listed. The following are listed alphabetically. When choosing a pesticide, consider
information relating to environmental impact, resistance management, the pesticide's properties, and application timing. Tank mixes may be necessary to achieve desired control; see the table SUSCEPTIBILITY OF WEEDS TO
HERBICIDE CONTOL for information on specific weed control. Always read the label of the product being used.
PREEMERGENCE HERBICIDES
A.
ISOXABEN
(Gallery 75 DF)
0.9975 lb
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 21
COMMENTS: Apply preemergence or combine with a postemergence herbicide if young weeds are established. May be combined with other preemergence herbicides to control additional broadleaf weeds.
B.
ORYZALIN
(Surflan AS)
2–4 qt
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Combine with a postemergence herbicide if young weeds are present. May be combined with
other preemergence herbicides to control a broader spectrum of grasses and broadleaf weeds.
C.
PENDIMETHALIN
(Pendulum 3.3 EC)
2–3.96 lb a.i.
24
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Apply preemergence. May be combined with a postemergence herbicide if young weeds are
present. May be combined with other preemergence herbicides to control grasses and certain broadleaf weeds.
D.
PRODIAMINE
(Barricade)
0.65–1.495 lb
12
NA
WSSA MODE-OF-ACTION GROUP NUMBER1: 3
COMMENTS: Apply preemergence. May be combined with a postemergence herbicide if young weeds are
present. May be combined with other preemergence herbicides to control grasses and certain broadleaf weeds.
POSTEMERGENCE HERBICIDES
A.
DIQUAT
(Reward)
1–2 pt plus 16–32 oz nonionic
24
NA
surfactant/100 gal water
WSSA MODE-OF-ACTION GROUP NUMBER1: 22
COMMENTS: Apply 15–40 gal/acre or enough to wet young weeds. Apply when weeds are young for improved control.
B.
GLUFOSINATE
(Finale)
Spot application: 1.5 fl oz/1 gal water
12
NA
Broadcast application: 3 qt when weeds are less
than 6 inches tall or 5 qt when weeds are 6 inches
or taller.
WSSA MODE-OF-ACTION GROUP NUMBER1: 10
COMMENTS: Apply as directed spray under benches or on floors of the greenhouse or around the periphery
of the greenhouse. Do not have air circulation fans running. Apply using large droplets and low pressure to
avoid drift or contact with green leaves or stems. Do not use in greenhouses with edible crops.
C.
GLYPHOSATE
(Roundup Pro)
Annuals: 2 qt–1 gal/100gal water
4
NA
or 0.66–1.33 oz/gal water
Perennials: see comments
WSSA MODE-OF-ACTION GROUP NUMBER1: 9
COMMENTS: Apply lower rates to young weeds. Apply to perennials when in flower stage and the soil moisture is sufficient to maintain active growth of the weeds.
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1
‡
NA
Group numbers are assigned by the Weed Science Society of America (WSSA) according to different modes of action. Although weeds may exhibit multiple resistance across many groups, mode-of-action numbers are useful in planning mixtures
or rotations of herbicides with different modes of action. For more information, see http://www.hracglobal.com.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be
safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In
some cases, the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
Not applicable.
Weeds
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This material is partially based upon work supported by the Extension Service, U.S. Department of Agriculture, under
special project Section 3(d), Integrated Pest Management.
PRECAUTIONS FOR USING PESTICIDES
Pesticides are poisonous and must be used with caution. READ THE LABEL BEFORE OPENING A PESTICIDE
CONTAINER. Follow all label precautions and directions, including requirements for protective equipment. Apply pesticides only on the crops or in the situations listed on the label. Apply pesticides at the rates specified on the label or at
lower rates if suggested in this publication. In California, all agricultural uses of pesticides must be reported. Contact your
county agricultural commissioner for further details. Laws, regulations, and information concerning pesticides change
frequently. This publication reflects legal restrictions current on the date next to each pest's name.
Legal Responsibility. The user is legally responsible for any damage due to misuse of pesticides. Responsibility extends
to effects caused by drift, runoff, or residues.
Transportation. Do not ship or carry pesticides together with food or feed in a way that allows contamination of the edible items. Never transport pesticides in a closed passenger vehicle or in a closed cab.
Storage. Keep pesticides in original containers until used. Store them in a locked cabinet, building, or fenced area where
they are not accessible to children, unauthorized persons, pets, or livestock. DO NOT store pesticides with foods, feed,
fertilizers, or other materials that may become contaminated by the pesticides.
Container Disposal. Dispose of empty containers carefully. Never reuse them. Make sure empty containers are not accessible to children or animals. Never dispose of containers where they may contaminate water supplies or natural waterways. Consult your county agricultural commissioner for correct procedures for handling and disposal of large quantities
of empty containers.
Protection of Nonpest Animals and Plants. Many pesticides are toxic to useful or desirable animals, including honey
bees, natural enemies, fish, domestic animals, and birds. Crops and other plants may also be damaged by misapplied pesticides. Take precautions to protect nonpest species from direct exposure to pesticides and from contamination due to
drift, runoff, or residues. Certain rodenticides may pose a special hazard to animals that eat poisoned rodents.
Posting Treated Fields. For some materials, restricted entry intervals are established to protect field workers. Keep workers
out of the field for the required time after application and, when required by regulations, post the treated areas with signs
indicating the safe re-entry date. Check with your county agricultural commissioner for latest restricted entry interval.
Preharvest intervals. Some materials or rates cannot be used in certain crops within a specified time before harvest. Follow pesticide label instructions and allow the required time between application and harvest.
Permit Requirements. Many pesticides require a permit from the county agricultural commissioner before possession or
use. When such materials are recommended, they are marked with an asterisk (*) in the treatment tables or chemical sections of this publication.
Processed Crops. Some processors will not accept a crop treated with certain chemicals. If your crop is going to a processor, be sure to check with the processor before applying a pesticide.
Crop Injury. Certain chemicals may cause injury to crops (phytotoxicity) under certain conditions. Always consult the
label for limitations. Before applying any pesticide, take into account the stage of plant development, the soil type and
condition, the temperature, moisture, and wind. Injury may also result from the use of incompatible materials.
Personal Safety. Follow label directions carefully. Avoid splashing, spilling, leaks, spray drift, and contamination of
clothing. NEVER eat, smoke, drink, or chew while using pesticides. Provide for emergency medical care IN ADVANCE as
required by regulation.
ANR NONDISCRIMINATION AND AFFIRMATIVE ACTION POLICY STATEMENT FOR UNIVERSITY OF
CALIFORNIA PUBLICATIONS REGARDING PROGRAM PRACTICES
The University of California prohibits discrimination or harassment of any person on the basis of race, color, national origin, religion, sex, gender identity, pregnancy (including childbirth, and medical conditions related to pregnancy or childbirth), physical or mental disability, medical condition (cancerrelated or genetic characteristics), ancestry, marital status, age, sexual orientation, citizenship, or service in the uniformed services (as defined by the
Uniformed Services Employment and Reemployment Rights Act of 1994: service in the uniformed services includes membership, application for membership, performance of service, application for service, or obligation for service in the uniformed services) in any of its programs or activities. University
policy also prohibits reprisal or retaliation against any person in any of its programs or activities for making a complaint of discrimination or sexual harassment or for using or participating in the investigation or resolution process of any such complaint. University policy is intended to be consistent with
the provisions of applicable State and Federal laws. Inquiries regarding the University's nondiscrimination policies may be directed to the Affirmative
Action/Equal Opportunity Director, University of California, Agriculture and Natural Resources, 1111 Franklin Street, 6th Floor, Oakland, CA 94607,
(510) 987-0096.
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