Diseases of basil and mint

Fungal diseases
of basil and
Mint
Fahnaz Sultana
M.Sc 1st year
Dept. Of Plant Pathology

Introduction
Basil or Tulsi is an excellent shrub and known as “Queen of herbs”
belong to the family of “Lamiaceae”.
Most of the Indians grow these plants in their houses and worship this
plant and also used in production of oil.
The parts of Tulsi generally used are its leaves, seeds and dried roots.
This plant also has many medicinal properties mainly used in Ayurvedic
medicines. Which made this plant popular.
Leaves are also used to make “Tulsi tea”.
In India, commercial/Organic cultivation is done in very large scale.

Basil leaves Basil plant flowering
Close-up of basil flowers

Downy mildew
Peronospora belbahrii
Symptoms :
Yellowing leaves
discoloration often begins around
middle vein and spreads outwards.
As the disease progresses, the more
characteristic symptom of fuzzy grayish-
purple sporangia (the reproductive
structures) develop on the lower surface
of the leaves.
 brown to black angular necrotic
patches on the plant.

Dark-colored fungal growth (sign) on the bottom
surface of a basil leaf.
Chlorotic (yellow) patches (symptoms) on the
upper surface of a basil leaf with downy mildew

Fruiting Bodies (sporangia) on lower
surface of leaf
Heavy spore production on the undersurface
of the leaf may look like dust or dirt on the
tissue.

Disease Cycle:
The disease is most likely introduced and spread
through contaminated seeds, infected leaves on the
market and wind-dispersed spores (Infected basil leaves
can produce lots of spores which could be dispersed
long distance).
Favourable conditions:
Moderate to warm temperatures
High humidity.

Management:
Grow tolerant varieties
Apply protective fungicide
Ensure good air circulation around greenhouse grown plants
Use drip irrigation to avoid wetting foliage.
In the field or garden, good sanitation practices should be used
to minimize inoculum levels.

Fusarium oxysporum f. sp. basilicum
Symptoms:
 Stunted growth
 Wilted and yellowing leaves
 Brown spots or streaks on the stem
 Severely twisted stems
 Sudden leaf drop
Fusarium wilt

Disease Cycle:
This is the most devastating fungal disease of basil.
It is a soil borne pathogen.
This disease may be introduced into the field or spread by
contaminated seeds or movement of soil where infected plants
have been growing.
Once established, the fungus can overwinter and survive for
many years as spores and cause new infections if basil or other
members of the mint family are re-planted.

Favourable conditions:
Disease favors warm, wet conditions.
Management:
Use only disease free seed
Treat seeds with hot water to kill fungi prior to planting.
If present in field, rotate crop every 2-3 years with crop other
than basil or mint.
Remove infected plant immediately to reduce the spread of
this disease.
Mulch can also help to reduce the disease incidence.

Cercospora leaf spot
Cercospora ocimicola
Symptoms :
Circular to irregular dark spots on leaves with light centers.

Management:
Avoid overhead irrigation and splashing plants with water.
Apply a layer of mulch around the plants to reduce water splash.
Remove and destroy any symptomatic leaves.
Minor infections can be controlled by spraying weekly with a
fungicide containing potassium bicarbonate.

Gray mold
Botrytis cinerea
Symptoms:
The most characteristic symptoms are a brown to gray fungal
growth on both leaves and stems.
This growth usually appears as a more dense fuzzy mold than
downy mildew.
Diseased leaves die and eventually fall from the plant.
If severe lesions develop on main stem, the infected plant may
die.

Gray mold infected basil stem Conidiophores with conidia arising
from infected tissue

Favourable condition:
Promoted by high humidity
Poor air circulation
Moderately cool temperatures
Management:
No chemical treatment available.
Avoid working in field in rainy conditions.
Remove infested leaves and/or plants.
Avoid overhead irrigation.

Damping off/Root rot:
Rhizoctonia solani
Pythium spp.
Symptoms:
Failure of seeds to germinate.
Germinated seedlings collapsing.
Brown, shrivelled area at base of stem.
Roots brown and water-soaked.

Favourable condition:
Promoted by high humidity
Poor air circulation.
Management:
Plant seeds in sterile soil;
Plant basil in well-draining soils.

 Mints belong to the genus Mentha and comprise approximately 20
species in the plant family Lamiaceae and are grown for their leaves
which are widely used as a flavouring.
 Leaf colours range from dark green and gray-green to purple, blue and
sometimes pale yellow.
 The flowers are white to purple.
 The cultivation of mint originated from Brazil and China
 For the past four decades, mints are commercially cultivated in India.
 Other major producing countries are China. USA and Brazil and to a
smaller extent Thailand and Vietnam.
Introduction

Spearmint ( M. spicata)
Four species are there
Japanese mint ( M. arvensis) Peppermint ( M. piperita)
Bergamot mint ( M. citrata)

Symptoms:
Small, dusty, bright orange, yellow
or brown pustules on undersides
of leaves.
New shoots may be pale and
distorted.
Large areas of leaf tissue die.
Leaves may drop from plant.
Mint rust
Puccinia menthae

Management:
Infected plants and rhizomes should be removed to
prevent spread
Heat treatment of roots may help to control the disease
Roots should be immersed in hot water at 44°C (111°F)
for 10 minutes, cooled using cool water and then planted
as usual
 Sulphur dust of 400 mesh fineness when applied at the
rate of 15 kg per hectare at weekly interval, gives
effective control.

Leaf blight
Symptoms:
On the leaves, spots of varying size appear.
The spots are irregular, brown to dark brown in color, and
have concentric lines inside the spots
Often several spots coalesce to form large patches, resulting
in the leaf blight.
In severe cases the entire foliage is blighted.
.
Alternaria spp.

Management:
•Fungicidal sprays, preferably with copper fungicides or zineb
given at 15 day interval effectively control the disease.

Verticillium wilt
Symptoms:
First, upper leaves twist and curl.
Leaves are bunched at the top of the plant.
Infected plants are stunted and foliage is yellowish to red
or bronze.
Lower leaves die first, then the aboveground part of the
plant.
Verticillium dahliae

wilting symptoms This section of field shows plant die-out due
to Verticillium wilt.

Management:
Use certified Verticillium-free stock for new plantings.
Application of Benlate, Bavistin and Topsin @ 0.1% .
Field sanitation.
Use of biopesticides ( Trichoderma formulation) @ 0.2%

Stolon Rot
Macrophomina phaseoli
Symptoms:
During rainy season, stolon rot occurs on the underground parts.
Infected stolons show brown
lesions which enlarge and turn
black, resulting in a soft decay.

Management:
Avoid excess irrigation.
Uproot and burn the affected plants.
Apply Trichoderma sp. to soil.
Crop rotation : 3 year rotation with rice, wheat and mint.
Treatment of the stolons with 0.25% solution of Captan or
0.1% Benlate for 2 to 3 minutes before planting is a preventive
measure.

Diseases of basil and mint

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