Leaf curl and leaf gall are the more serious of the leaf blister diseases.
Leaves become puffy and the tissue is thickened, puckered and brittle.
The puckering distorts the shape of the leaf, causing it to curl. Often the puckered areas are different colors than the green leaf tissues. This fungus invisibly remains on the bare branches after leaves have fallen and multiplies there in early spring. Rains splash the fungus onto emerging leaves. The disease is most severe when leaf emergence and elongation occur during rainy weather.