Downy mildew appears on plants and trees as small yellow spots on the upper surfaces of leaves and the underside of the leaf is covered with white, cottony growth. The yellow spots appear initially on older leaves and gradually turn brown and brittle.
Downy Mildew is very prevalent on grape vines and causes leaf wilting and inhibits the fruit from maturing. The fungus that causes Downy Mildew (Plasmopara viticola) over-winters on fallen diseased leaves.
To control Downy Mildew, in the fall, it is important to collect and remove all fallen leaves and follage. At the first sign of the disease in the spring or early summer, spray the affected tree or vine with Captan Fungicide. Repeat the spray evey 10 days during the growing season. To prevent the spread of Downy Mildew, spray susceptible plants located in close proximity to diseased trees and plants.