Seridium cardinale
As with Monterey cypress, disease development on Leyland cypress has been closely tied with hot, dry summer weather.
This disease has also emerged across the Southeast as a common and damaging disease in landscape plantings and on Christmas tree plantations. As was the case with Monterey cypress, disease development on Leyland cypress has been closely tied with hot, dry summer weather. Two other species of Seridium, S. unicornie and S. cupressi, are also known to cause canker diseases in juniper and cypress.
The most noticeable symptom of Seridium canker is yellowing or browning of the foliage on one or more top or lateral branches. This discoloration may appear at any time of the year but is most likely to be seen in the spring. Disease development often continues until a considerable portion of the tree is killed.
Girdling cankers form on the twigs, the scaffold branches, and the main trunk, and then the foliage dies.
The spores are spread to healthy foliage and branches of adjacent Leyland cypress by splashing water and contaminated pruning tools.
Valsa kunzei (Cytospora kunzei) (fungus), V. nivea (C. nivea), V. sordida (C. chrysosperma)
Affected trees include aspen, cherry, elm, fir, maple, mountain ash, poplar, spruce, and willow throughout the Continental United States and Canada.
Wounding, improper pruning, poor ventilation, and moist atmosphere are causes.
Cytospora is irregular diffuse to the cankers on/and girdling trunks and large branches, from which yellow to red-brown spore horns or tendrils develop in moist spring weather; diseased bark discolored with black pimples; sapwood red-brown and water-soaked; wilting and dis-coloration of leaves often accompanies canker formation, followed by dieback of small branches and twigs. Needles of spruce and fir become yellow-green to purple, progressing up crown; copious resin flow from infected branches, coating cankers. Spruce cankers slightly swollen.
Spores contact wounds or branch stubs and germinate in moist atmosphere; living wood is invaded where the fungus becomes established at periphery of dead and live wood. New spores are produced in flask-shaped fruiting structures (pycnidia). Waxy tendrils release spores when wet to re-infect new wounds and branch stubs. Invasion by spores is direct or through needle scars in spruce and fir. Spores are either airborne or spread by insects, clothing, or pruning tools.
Diplocarpon mespili (imperfect stage), AKA Hawthorn Leaf Spot
Found to be throughout North America and Europe.
Favored by cool, wet weather. Predictable outbreaks based on temperature and moisture conditions. During cool, wet weather (60o to 80o F., 12-24 hour leaf wetness), small, circular, often bright red spots appear on leaves of red tip photinias and hawthorns. Many small spots may grow together to form large maroon blotches on heavily diseased leaves. Severe infections cause early and heavy defoliation, greatly reducing the landscape screening value and increasing the plant’s sensitivity to cold injury, other diseases and insects. Isolated plants or hedges often remain healthy since the fungal spores only splash over short distances.
Occuring in northern areas, but may continue year-round in regions with a mild winter climate, on evergreen hosts such as Indian and Yedda hawthorn, loquat, photinia, stranvaesia, and toyon. On deciduous hosts, the fungus may persist through winter in lesions on young, green twigs. From either year‑old leaves or twigs, conidia are splashed to developing leaves in spring. Conidia can also survive winter in acervuli on fallen leaves, and some new conidia are produced there in spring. Primary infection begins when spores are splashed onto new leaves. Thereafter, many repeating (secondary) cycles of disease start successive generations of conidia, causing new lesions.
Found on Austrian, ponderosa, and Scots pines most susceptible. Other pines less susceptible. Other conifers: deodar cedar, fir, eastern larch, hoop pine (Araucaria cunninghamii); Colorado blue, Norway, and white spruce and worldwide. Most severe on trees out of range.
Contributing to infections are drought, soil compaction, root damage, excess shade or heat, urban heat reflection (disease rare in normal forest conditions), Favorable temperature 82∞ F.
Exudation of resin drop from growing tip. Buds stunted during needle elongation; needles yellow-green to straw color. Tissues in elongating lesions water soaked, dark red-brown, exuding resin. Resin hardens, making tips hard and brittle. Repeated annual infections deform crown. In severe cases pycnidia evident beneath bark scales as black pads with gray mycelium. In second year of development, infected cone scales are covered with black pycnidia.
Dark brown conidia, appearing as brown specks at tips of pycnidia under needle sheaths, are splashed around by rains from early spring to late fall and enter directly into needle and bud tissues to create new infections. Lesions around infection sites grow rapidly into twigs below the needles for about 3 weeks in the spring when the buds elongate. Resin exudes from lesions, buds, or elongating twigs and needles die. Resin oozes around the affected area. Wounding by spittlebug or nodule moth creates sites for spores and development of larger resinous cankers on stems or larger branches, resulting in severe damage. Cones invaded by spores when buds develop pycnidia, and conidia the second year, are responsible for copious spore showers.
The Larvae are Segmented, with small black head, 1 1/2 – 2 in. long; cream to pink.
The Adults are 3/4-1 1/2 in. long; usually yellow with 3 black spots on thorax, their wing covers black along sides and down the middle.
Their Favorite host are dogwoods with occasionaly viburnum, Ulmus, malus, and prunus spp.
In the United States their found Eastern coastal, southern central and in the southwest, within the range of dogwood.
Poor sites, drought, nutritional deficiencies, wounding or root compaction all contribute to infestations.
The symptoms include Twig die-back, often severe; center of branch hollow from larval feeding and an occasional long series of round holes in bark with frass exuding; parts of twig cut off from within.
Adults emerge in early summer, feeding on twig tips; after girdling twig, adult deposits eggs inside; larvae feed down center of twig or branch, making long series of round holes for exuding frass; at intervals they cut off portions of the twig from within, then proceeds to feed downward in green wood; pupation between two wads of frass; the portion containing the cell sometimes is girdled; development usually is completed within one year.
Common to American elms. Occasionally on slippery and Siberian elms located in central and eastern United States.
Wounding, insect punctures, pruning, compacted soil, drought, malnutrition, overhead irrigation, climbing spurs all add to infections.
The foliage yellows and wilts in scattered portions of crown with wilt becoming generalized throughout, followed by gradual dieback. Outer rings of wood have brown discoloration. Elliptical cankers on stems with small black specks of spore bodies (pycnidia). In wet weather, sticky spore masses accumulate around wounds or on leaves. Wilt symptoms resemble those caused by other wilt fungi. Laboratory isolation is necessary for positive diagnosis and identification.
There are sticky spore masses on leaves or twigs spread by wind, rain, overhead irrigation, and pruning. Infection usually through wounds on leaves, but may enter through stem wounds. The fungus moves down leaf petioles into twigs, entering and plugging vessels. Cankers develop around such infection sites. New pycnidia develop during summer and autumn, releasing spores during spring rains.
Their Larvae is yellow-white with black head capsule in first instar; pink to yellow with brown head capsule in final instar. They pupate or overwinter near axis of cone in papery resin-coated cocoon perpendicular to cone axis among resin-coated scales. The adults are Moth about 1/2 in. long. Silvery gray with dark russet-brown traverse stripes on forewings; wingspan 1/4-3/4 in.
They infest Douglas fir trees as their name implies.
In the United States they can be found on the West coast and Rocky Mountains and in British Columbia.
Poor sites, drought, nutritional deficiencies, heavy cone crop all contribute to infestations.
They extrude resinous exudations between scales and cones may be misshapen (distored), with frass on the surface.Their Flight happens in early spring with eggs deposited on protruding bracts of young cones in May to early June. Young hatching larvae reach cone scales by boring into bracts through a torturous resinous tunnel, with an opening at the surface through which resin and larval castings are exuded. Feed first on scales, then the seeds for about 2 months. Cone is not killed by initial attack, but heavily infested cones usually wither before maturing. Resinous exudations between the scales prevent opening to release uninjured seeds. Pupae form in July and August. Moths emerge in April and May of the following spring. One generation annually, with part of the brood retarded as pupae, passing through a biennial generation.
The Larvae is Yellow-white with black head capsule in first instar; pink to yellow with brown head capsule in final instar.
Afterwards they pupate or overwinter near axis of cone in papery resin-coated cocoon perpendicular to cone axis among resin-coated scales.
The adults are Moth about 1/2 in. long. Silvery gray with dark russet-brown traverse stripes on forewings; wingspan 1/4-3/4 in.
Infesting Douglas fir trees in the United States they can be found on the West coast and Rocky Mountains and in British Columbia.
Poor sites, drought, nutritional deficiencies, heavy cone crop all contribute to infestations.
They extrude resinous exudations between scales and cones may be misshapen (distored), with frass on the surface.
Adult Flight occurs in early spring with eggs deposited on protruding bracts of young cones in May to early June.
Young larvae reach cone scales by boring into bracts through a torturous resinous tunnel, with an opening at the surface through which resin and larval castings are exuded. Feed first on scales, then the seeds for about 2 months. Cone is not killed by initial attack, but heavily infested cones usually wither before maturing. Resinous exudations between the scales prevent opening to release uninjured seeds. Pupae form in July and August. Moths emerge in April and May of the following spring.
There is one generation annually, with part of the brood retarded as pupae, passing through a biennial generation.
Contarinia pseudotsuga
Douglas-fir cone gall midge is considered the most significant pest of Douglas-fir seed orchards and can destroy up to 70 percent of the seed crop.
The midge can be found in plantings of Douglas fir trees.
Maggots in the galls are orange in color and about 2mm long. Adult males have bright orange abdomens, beaded-antennae that are approximately as long as the body, and they are 2.3 to 2.8 mm in length.
Larval or maggot feeding causes a gall in the vicinity of the seed. This can kill the seed or fuse it to the cone scale and it can’t be shed or extracted. All seeds in heavily infested cones can be destroyed. This pest is persistent in Douglas-fir seed orchards throughout the Northern Regions.
Douglas-fir needle midge overwinters as larvae in soil under infested trees. In early spring, larvae pupate and adult midges emerge as buds are expanding. In Oregon and Washington, where this fly has been a pest for many years, emergence may start as early as the beginning of April and continue for 4-5 weeks.
Female midges have long ovipositors with which they place several orange eggs in expanding buds and on elongating needles.
Larvae hatching from the eggs chew into the needle, causing elongating needles to form a gall around the larvae. One or more white maggotscan be found inside affected needles during the summer. At the site of the gall, the needle is frequently bent .
The damaged area is initially pale in color but as the season progresses, will darken and eventually turn brown. In late summer, larvae emerge from the undersides of the needle and drop to the soil. The emergence holes are irregular in shape and may give the appearance of a slit or rupture. Secondary fungus can infect the needle and gall, further complicating identification of the pest .
Douglas fir trees throughout California and Oregon.
Malnutrition, improper irrigation, poor soils, construction stress, persistent rainy or foggy weather; wounding by squirrels, birds, improper pruning, and climbing spurs. Long, narrow cankers on branches, usually pointed at ends; may girdle entire branch in one season. Usually in saplings on poor sites, but it may attack individual branches in mature ornamental trees under stress.
The fungus may enter through needle scars or wounds. It girdles branches and is usually successful in stressed trees. Cankers are established at the point of infection. During wet season, spores are produced in spore fruits (pycnidia) at the edges of the cankers from which they spread to other parts of the tree, or to adjacent trees.
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