Management of downy mildew in grape

Management of downy mildew in grape
Downy mildew is a highly destructive fungal disease of grapevines in all grape-growing areas of the world. Economic losses are associated with cluster destruction and loss of vine foliage resulting in the loss of photosynthetic area. Disease symptoms
Initial symptoms are light greenish yellow oily spots on the upper surface of the leaves.
These spots enlarge and coalesce to cover the entire leaf surface. On the corresponding lower surface glistening white downy growth of the fungus is seen which is more prominent in the humid weather.
In severe infection, the entire lower surface of the leaf would be covered with the dirty white downy growth of the fungus.
Severely affected leaves fall prematurely. Young shoots and tendrils turn brown and become stunted and distorted.
They become soft, emit fishy odour and are often swollen and may curl. Older shoots and nodes are more susceptible than internodes.
Flower clusters are highly susceptible. Infected inflorescences turn oily yellow to brown and may become whitish during periods of high humidity at night.
Sometimes only a part of the bunch is affected. When infection occurs early, clusters are covered with a grey mat of fungal material, which leads to rotting of berries.
The fungus grows internally on these berries causing a condition referred to as brown rot.
Infected fruit on white varieties turns dull green and black fruited varieties turn red. Berries eventually turn brown, fail to soften and become slightly wrinkled. Disease management
Grapevine orchards should be established in well-drained sites with good air movement.
Planting in rows makes natural patterns of air movement minimize leaf wetness.
Use of overhead irrigation should be avoided. Reducing leaf litter and pruning may reduce the amount of over wintering inoculum.
Five sprays of Bordeaux mixture, Blitox-50 (0.3 per cent), Zineb, Maneb and Mancozeb (0.2 per cent) and captan (0.2-0.5 per cnt) can be applied. Mallikarjun
Y Kenganal
Hemavati Ranebennur
& Byadgi, A. S.
Department of Plant
Pathology, UAS, Dharwad