Walnut

From Bugwoodwiki

USDA Forest Service. 1979. A guide to common insects and diseases of forest trees in the northeastern United States. Northeast. Area State Priv. For., For. Insect and Disease Management., Broomall, PA. p. 123, illus.

Walnut anthracnose, caused by Gnomonia leptostyla, affects black walnut, butternut, Persian walnut, and first-generation hybrids of Persian and black walnut. Leaves, nuts, and sometimes shoots of the current season's growth are attacked.

The disease begins as tiny, dark spots on infected leaves. These spots usually spread over the leaves until they form large dead areas or blotches. Yellowish to gold leaf tissues usually border these spots.

Anthracnose can be epidemic in wet weather, causing premature foliage loss as early as late July or early August. Such defoliation slows the tree's growth, weakens the tree, and sometimes kills it. The nuts of diseased trees have dark, unattractive, shriveled meats and sunken dead spots on the hull. The fungus overwinters in infected leaves on the ground.