Infected berries turn from light brown to dark brown, then shrivel and turn hard and black. The hard black mummies remain firmly attached to the cluster. Tiny black fruiting bodies can also be seen on the shriveling berries and on the hard, black mummies. Infected fruit will contaminate wine. Upper leaf surfaces develop yellowish lesions, while lower surfaces develop a white, downy sporulation, especially along veins.
Severe infection leads to defoliation.
Infected fruit turn light brown to purple, then shrivel and detach easily. With high RH, white cottony sporulation will occur on fruit. Many grapes are susceptible to downy mildew, with Chardonnay, Riesling, Catawba, Delaware and Niagara highly susceptible. Lesions on shoots are most common, although leaves and fruit can become infected. Elliptical lesions develop on the lower part of the shoot.