Downy Mildew

The Causal organism: Plasmopara Viticola

Symptoms:
-The casual fungus attacks all green parts of the vine, particularly the leaves. Depending on incubation period and leaf age, lesions are yellowish and oily or angular, yellow to reddish brown, and limited by the vine.
-Sporulation of the fungus- a delicate, dense, white, cottony growth occurs on the lower leaf surface. Leaf infection is most impotent as a source of inoculums for berry infection and as over wintering inoculums. Severely infected leaves generally drop. Such defoliation reduces of over wintering buds.
-Infected shoot tips thicken, curl, and become white with sporulation; they eventually turn brown and die.
-The young berries are highly susceptible, appearing grayish when infected (gray rot) and covered0 with a downy felt of fungus sporulation.

Disease Cycle:
-Plasmopara Viticola over winters mainly as oospores in fallen leaves, although it can survive as mycelium in buds and in persistent leaves.
– Sporangiophores and sporangia are produced only through the stomata on the over leaf surface, a process that requires 95-100% RH. And at least 4hr.of darkness.
– The optimal temperature for sporulation is 18-22C.

Activities related to cleaning of vineyards

Cloudy conditions, possibility of thunderstorms, increase in RH will be the main highlights of weather during coming 7 days. North part of Nasik it may rain and hence RH will increase in Nasik district. The cloudy conditions for few days reduce the temperatures but after 4 to 5 days temperature will increase again. Windy condition during most of the days will not allow higher RH for long time. Continue reading “Activities related to cleaning of vineyards”