Defoliation can be severe when conditions favor disease development. Fertilize infected trees and prune out infected branches. Coccomyces hiemalis causes reddish spots which drop out leaving shot holes. Once the holes appear the leaves may drop. The disease is worse in wet weather.
Black knot causes black swellings or galls on the branches.
Branches with galls are pruned out. Powdery mildew causes a white coating on the leaves. Use benomyl to control the disease. Yoshino cherry may be subject to witches broom caused by Taphrina cerasi. Branches are deformed and clusters of small branches form.