PEACH LEAF CURL                                Bulletin #5098

Introduction

Peach leaf curl is caused by the fungus Taphrina deformans. It occurs commonly in Maine and both nectarines and peaches are affected. Although this fungus can infect the fruit, most losses are due to reduced vigor caused by defoliation. Subsequent refoliation uses energy reserves which would otherwise be used to produce fruit. The weakened trees are also more susceptible to winter injury. When the fruit is infected, it is likely to drop before maturity.

Symptoms

As the name implies, the disease is expressed as distorted or curled leaf tissue. These puckered, thickened leaves often have a characteristic reddish-purple color where the distortions occur. These symptoms may begin early in the season as the leaves are unfolding. Later the color turns to a powdery gray on the upper leaf surface as the fungus begins to produce spores. As the season progresses and the weather turns warmer and drier, the leaves turn yellow and dry and finally drop from the tree.

Young twigs can also be infected. They are stunted and may be distorted and thickened and may die. Leaves that grow from such twigs are also stunted and distorted. Infected twigs tend to die easily. Fruit infections are not common but appear as wrinkled or swollen reddish lesions which lack the normal peach fuzz.

Survival and Dispersal

Spores that  form on the surface of the leaf are the overwintering stage of the fungus. These spores are dispersed by the wind and splashing rain. They land in the cracks and crevices of the tree and in the bud scales where they rest until the following season. In the spring, spore germination is timed to coincide with the emergence of the leaf tissue. These initial spores (ascospores) germinate to produce another spore type (blastospores) which reproduce by budding. The spores fall onto susceptible tissues and germinate to penetrate the tissue directly.

As with most fungi, water is very important to the infection process. Wet weather during bud-break and leaf emergence is favorable to the disease. Because infections can begin at temperatures below 50^oF, cool weather is thought to extend the infection period because the new leaves expand slowly.

Control

Peach leaf curl is readily controlled. There are no non-chemical controls which have proved effective (e.g. sanitation, resistance), however, effective control can be achieved with one or at most two fungicide treatments. Spray either in the fall just before defoliation normally occurs or in the spring just before the buds begin to swell or at both times if the problem is severe. Some fungicides which are effective include: chlorothalonil, Bordeaux mixture, lime sulfur, and fixed coppers.

When Using Pesticides  ALWAYS FOLLOW  LABEL DIRECTIONS! Bruce A. Watt, Extension Plant Pathologist 2004 Where trade names are used, no discrimination  is intended and no endorsement by Cooperative  Extension is implied.

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