The disease first shows up as slight yellowing of infected tissue. This is followed by the formation of circular, raised blisters. On the bottom of leaves, this has a particular rough and gray appearance. Dead tissue will eventual turn brown and leaves drop prematurely. The fungus survives on bud scales and in bark crevasses as well as on fallen leaves.
Infection occurs in the early spring as leaf buds begin to develop.
Heavy infections occur following cool, wet springs. Defoliation can be severe in mid-summer and will weaken trees and make then susceptible to other problems. Use of fungicides is not recommended. The fungus will not spread now. Infection next year is based on weather conditions next spring.