Anthracnose is beginning to cause some defoliation now. Small brown blotches can be see on the individual leaflets, which later yellow and drop. There has been some research that indicates that nitrogen applications in the spring can reduce severity of anthracnose in the fall if nitrogen fertility is low or trees have not been fertilized in a long time or ever. Other foliage diseases are a minor problem at this time. But, black spot on American elm, Septoria leafspolt on river birch, Entomosporium leafspot on hawthorn are present on susceptible plants.
Black spot produces very small black crusty spots on the upper surface of American elm leaves.
Septoria on river birch produces small circular spots with tan centers on the leaves, and Entomosporium on hawthorn produces small dark, angular spots, often with yellow borders on susceptible hawthorns. All three diseases usually do not need to be controlled with fungicides. Raking and removing or composting fallen leaves in the fall will help control for next season. Apply Cleary's 3336, Immunox, Bayleton, Eagle, Banner, triforme, or other labeled fungicide when mildew is first seen. What's Hot The Summer Turf and Nursery Expo, sponsored by DAN and DE Coop.