In some cases, every leaf on a tree may be infected. The diseased areas develop a powdery gray coating and leaves may then turn brown, wither, and drop from the tree. Twig and fruit infection, which is less conspicuous, can also occur. Yearly defoliation resulting from peach leaf curl or plum pockets can seriously weaken the trees and make them more sensitive to cold injury. Peach leaf curl is caused by a fungus called Taphrina deformans .
Infection occurs during the spring just as the buds begin to swell.
Spring rains wash spores of the fungus to the surface of leaf buds and provide conditions for spores to multiply. Once the bud scales loosen in spring, spores are carried in water films to the emerging leaf tissue where infection takes place. After infection occurs in late winter or early spring, there is no further spread of the disease during that season. The tips of the plum shoots appear swollen and are often twisted and curled. The fruit frequently appears swollen, misshapen, and bladder-like with thick spongy flesh.