Peach leaf curl is prevalent this spring. The fungal pathogen, Taphrina deformans, causes leaf puckering and unusual coloration, with bright red, yellow, lime green, or a combination of all three colors on one leaf. Infection occurs at bud swell and bud break, when spores, overwintering on twigs and buds, infect emerging leaves. The distortion of leaves inhibits photosynthesis and early defoliation occurs, all of which affects the tree’s ability to produce peaches. If infection is severe and occurs over several growing seasons, the disease weakens the tree.
Cool, wet springs are highly conducive to the development of peach leaf curl on peaches and nectarines. While the disease tends not to infect the fruits, fungal infection of the fruit is possible when temperatures and precipitation levels continue to favor the pathogen. As the disease matures, leaves become thickened and covered in powdery spores. Affected leaves may drop from the tree or continue to hang on branches.
Once the fungus is present on leaves, fungicide applications do not provide much in the way of protection or control. The key to keeping disease incidence low is to target overwintering spores. Dormant oil is a heavy, viscous oil that works by suffocating fungal spores on twigs and buds. Applications are best applied twice, once in late November and the second in late March when temperatures are above freezing. Other fungicide options include chlorothalonil and copper-containing fungicides.