Anthracnoses

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.

The hardwood tree leaf diseases called anthracnoses are caused by fungi of the genera Gloeosporium and Gnomonia. Affected host trees include ash, basswood, birch, catalpa, elm, hickory, horsechestnut, maple, oak, London plane, sycamore, yellow-poplar, and walnut. The disease is particularly harmful to American sycamore, white oak, other oaks in white group, and black walnut. Symptoms generally include dead spots on the leaves or dead leaves, premature defoliaton, formation of twig cankers, and twig dieback.

The fungi that cause anthracnoses have both sexual and asexual stages. The fruiting bodies appear as tiny specks on killed areas. The fungi overwinter in fallen leaves and cankered twigs still on the tree. Sexual spores, produced in small, dark, fruiting bodies on these leaves or twigs, are responsible for infection in the spring. Air currents carry the spores to newly developing leaves. Late-summer infections arise from asexual spores produced in the spring. The spores are splashed about by rain, causing new infections.