PATH 372 Diseases of Horticultural Crops

Grow resistant varieties like Banglore blue, Golden muscat, Golden queen and
Isabella.
4. Alternaria leaf spot: Alternaria vitis
Symptoms
Appearance of patches mostly along the margin of leaves
Individual spots appear rarely in the middle of the leaves
In the initial stage, minute, yellow spots appear on the upper surface of leaves
Later, spots enlarge and form brownish spots with concentric rings in them
In severe cases of attack, leaves dry completely and defoliation occurs
Mode of spread and survival
Survives as mycelium or conidia in infected plant debris
Spreads through air borne conidia
Favourable conditions
High humidity
High rainfall and dew
Heavy dosage of N2 fertilizers
Management
Destruction of crop debris
Selection of disease free seed
ST with mancozeb@2g/kg seed
Foliar spray of mancozeb@0.25%
5. Bacterial leaf spot: Pseudomonas viticola
First reported from S.V. Ag. College, Tirupati (1969 – 70).
Anab-e shahi & Thomson seed less varieties are highly susceptible
Symptoms
Symptoms appear on foliage and twigs
Initially yellowish, circular, translucent spots develop along the midrib and veins
of leaves
Necrotic areas along midrib & veins is the characteristic symptom
Leaves turn yellow, shriveled and shed pre-maturely
Disease cycle
P.I: Mainly from infected twigs. Bacterium survives in the soil on plant debris.
S.I Through wind splashed rain.
Management
Prune out and destroy infected plant debris
Spraying antibiotics like streptomycin 100 ppm along with copper fungicides
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