Peach leaves showing symptoms of the disease peach leaf curl have been arriving in the Plant Disease Clinic. This disease causes leaves to become puckered, thickened, and show a reddish color. Infected leaves turn gray and eventually wither and fall from the tree. Because early defoliation occurs, peach leaf curl can reduce peach tree vigor and fruit yields. The disease may also occur on fruit, blossoms, and young twigs. Infected shoots appear stunted, swollen, and chlorotic. Diseased fruits show raised, wrinkled areas and often fall prematurely.
The fungus that causes peach leaf curl, Taphrina deformans, overwinters on buds scales and twigs. Infection occurs during the spring just as the buds begin to swell. Spring rains wash spores of the fungus to newly emerging leaf tissue. Cool, wet conditions favor the disease.
Fortunately, the disease is fairly easy to control with a single fungicide application. Timing is critical. Because infection occurs when the buds begin to swell, the fungicide must be applied during the dormant season, either after leaf drop in the fall or in late winter before buds begin to swell. Once the current year's leaves become infected, they cannot be treated. Fungicides effective for controlling peach leaf curl include lime- sulfer, Bordeaux mixture, chorothalonil (e.g. Daconil 2787), or ferbam (Carbamate WDG).
This article originally appeared in the June 17, 1994 issue, p. 92.