Purdue Extension Service

Vanderburgh County, Indiana

Peach Leaf Curl: Noticeable, But Not Dangerous

By Larry Caplan, Extension Horticulture Educator, Vanderburgh County, IN

For the Evansville Courier and Press, May 10, 2009

I've had several samples of distorted peach leaves brought to my office this past week. A quick glance through one of my disease books confirmed that we had an outbreak of peach leaf curl, a fungus disease.

Peach leaf curl is first noticed early in the spring when leaves start to unfold. Diseased leaves are noticeably red and soon become distorted, thickened, and greatly curled as they develop. When diseased leaves are fully developed, they are lighter colored than normal; frequently flushed with red; and greatly curled, puckered, and distorted. Leaves infected with leaf curl are also thicker than normal leaves and have a firm and leathery consistency.

The disease causes loss of foliage early in the summer. This stimulates the affected tree to produce another crop of leaves, resulting in decreased tree vigor. Lowered tree vigor usually increases the danger of winter injury.

Young infected peach fruits become distorted and seldom remain on the tree very long. Infected fruits show irregular, swollen, colored areas on their surfaces. These areas are usually wrinkled, without the normal peach fuzz, and look like they have been polished.

Peach leaf curl is caused by the fungus Taphrina deformans. Spores of the fungus are produced on the surface of diseased leaves in midsummer and give the leaf a powdery appearance. These spores are spread to all parts of the tree by winds and rains, becoming lodged under bud scales and rough bark, and here they remain throughout the summer and winter months. In the spring, when the young peach buds begin to swell, germinating spores of the fungus penetrate the young leaves, causing leaf curl infection.

Peach leaf curl can be prevented by a single spray application made in late fall, after leaf drop, or in late winter, BEFORE bud swell. If buds have begun to swell or open, it is too late to obtain satisfactory control of peach leaf curl as infection has already occurred. Control is impossible once symptoms are visible.

Fungicides registered for control of peach leaf curl include liquid limesulfur, chlorothalonil (Daconil), and copper-based fungicides (numerous trade names are available) including
Bordeaux mixture. Follow all label instructions regarding amounts of pesticide to use, method of application, and safety warnings.

If a dormant spray has been neglected, and disease develops, the fruit on affected trees should be thinned to compensate for the loss of leaves. In addition, fertilize and water trees to help maintain tree vigor - and be sure to get a leaf curl spray on next year!

For more information on diseases and insects of fruit trees, please contact the Purdue Extension Service at (812) 435-5287.