A certified arborist should be contacted if chemical control is needed. On the leaves, spots appear with pale yellow centers and purple borders. The spots are irregularly round and inch in diameter. Black fruiting bodies of the fungus develop in a circle in the centers of the spots. These fruiting bodies occur in greater numbers on the upper leaf surface.
Severe infection can result in partial defoliation of the tree.
Often the disease goes unnoticed until leaf accumulation occurs under the tree. The fungus survives the winter in fallen leaves. In the spring spores are produced and dispersed to the new leaves of susceptible trees. Rake up all fallen leaves. Fertilization and watering may help to reduce the disease.