Bacterial blight causes spots on the leaves and shoots. The spots later become sunken and turn black. Infected leaves are distorted and the shoots have black stripes. The leaves at the twig tips wilt and die. Prune out dead shoots in the fall.
In years favorable for leaf spots trees may be defoliated. Rake up and dispose of infected leaves.
Cankers cause dieback of branches and kill trees if the trunk is infected. Prune out infected branches and keep the trees healthy.
Powdery mildew causes a white coating on the leaves. Use benomyl according to label directions.