Ash Anthracnose Ash Anthracnose Anthracnose is a common foliage disease of shade trees in Iowa.
Symptoms occur on sycamore, ash, maple, oak, walnut, linden, hickory, and other deciduous trees.
Anthracnose is caused by a number of different but closely related fungi. Each fungus is specific to the host tree it affects. In most cases, although symptoms may appear serious, damage caused by anthracnose is minimal and does not seriously harm established shade trees. Symptoms vary from small, circular to irregular spots that are tan, dark brown, or black, to larger blotches that are usually associated with midribs and veins. When immature leaves are infected, these leaves may become distorted from abnormal leaf expansion.