Peach Leaf Curl

Patricia McManus and Brian Hudelson, UW-Madison Plant Pathology

What is peach leaf curl? Peach leaf curl, caused by the fungus Taphrina deformans, is a common disease on peach and nectarine trees throughout the Midwest and eastern U.S. Where symptoms are severe, tree vigor and fruit quality and yield are diminished. Reports of peach leaf curl have increased in recent years, possibly because relatively mild winters have favored the survival of the pathogen in bark and bud scales. A related disease, plum pockets, affects plums.

What does peach leaf curl look like? Diseased leaves are reddish to purple in color, and thickened, twisted, and generally distorted. Leaves later turn brown and fall from the tree. Diseased shoots show stunted growth with small, yellowish leaves, or leaves arranged in tight whorls (rosettes). Diseased fruit are bumpy, reddish in color, and fall prematurely.

How does peach leaf curl develop? The pathogen overwinters in bark and bud scales. Fungal spores infect leaves and shoots during spring while leaves are still in the bud and during bud burst. Mild (50-70 degrees), wet weather during this period favors infection. As the fungus grows in plant tissues, it disrupts normal cell development resulting in distorted, off-color leaves, shoots, and fruit. Additional spores form on the surface of diseased tissues, and these spores go on to start new infections if the weather remains mild and wet.

How do I save trees that have peach leaf curl? If significant premature leaf drop occurs, trees will be susceptible to drought stress and winter injury. To help maintain tree vigor, irrigate during dry periods, fertilize with nitrogen (but not later than July 1), and thin fruit if the crop load is heavy. Avoid late summer fertilization as this will prevent trees from hardening off thoroughly before winter.

How do I avoid problems with peach leaf curl in the future? No peach varieties are immune to peach leaf curl, but varieties derived from Redhaven are more resistant than varieties derived from Redskin. A single fungicide spray in the fall after leaf drop or in the spring before bud swell will control peach leaf curl and the related disease on plum, plum pockets. Effective fungicide active ingredients include chlorothalonil, copper (e.g., Bordeaux mixture), and ferbam.

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