Peach leaf curl has been a common disease problem this spring. As new leaves emerge and expand, they become puckered, curled, thickened, and often turn red or purple. Later in the season, upper surfaces of infected leaves turn gray. Infected leaves may wither and fall off in warm, dry weather.
Infection occurs as buds begin to swell and open in the spring. Spores of the fungus, which overwinter on bark and bud scales, wash onto the young leaf tissue in wet weather and initiate infections. Peach leaf curl tends to be most severe when buds open and leaves expand during wet periods.
Fruit yields are often reduced because the tree's energy is diverted into forming new leaves.
Applying a fungicide now will not be helpful, since the damage has already taken place. The disease can be controlled by a single fungicide application (bordeaux, chlorothalonil, copper, lime-sulfur, or sulfur) in the fall or just before bud break.
To improve tree vigor, provide water if extended dry conditions occur and reduce fruit load.
Photos of disease symptoms can be found on the ISU Extension Plant Pathology home page .
This article originally appeared in the June 11, 1999 issue, p. 77.