Leaf blotch can affect many types of grapes but is most often found on leaves of American rootstock cultivars. Leaf lesions appear after mid-season. Lesion size ranges from 1/25 inch to 2 inches (1 to 50 mm). Small lesions have dark margins, and large lesions have light-colored, zonate rings. Stalked fruiting structures are produced within 3 to 4 days of the appearance of the lesion, usually on the lower leaf surface. The fungus may also sporulate on overripe berries. The fungus overwinters in infected plant debris.
Leaf blotch is present throughout the eastern United States
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