Peach Leaf Curl Management

If you grow peach trees and during the summer you noticed red, distorted, thickened leaves that curl up and then drop off the tree, chances are you have peach leaf curl. This is one of the most common and widespread diseases affecting peach plantings. Although this fungus can infect the fruit, most losses are due to reduced vigor caused by defoliation. Typically tree’s send out a second set of leaves after a loss due to peach leaf curl. This uses energy reserves which would have been used to produce fruit. It also weakens the tree and makes it more susceptible to winter injury or other diseases. Weakened trees also produce fewer fruit the following season.

Peach leaf curl is caused by the fungus Taphrina deformans. It is first noticed in early spring when the leaves start to unfold. The developing leaves are thickened and puckered and have a reddish or purple cast. Later the color turns to a powdery gray on the upper leaf surface as the fungus produces spores. With warmer, drier air the leaves turn yellow and drop from the tree. Secondary leaves do not show any symptoms of the disease. Sometimes infected peach fruits will develop irregular, raised, colored areas then they too will fall off the tree.

The fungal spores that develop on the leaves, giving them that gray color, are spread to all parts of the tree or neighboring trees by wind and rain. The spores land on cracks and crevices and in bud scales where they remain throughout the summer and winter months. In the spring, spore germination is timed with the swelling of young peach buds. The spores then can enter the young leaves and cause infection. This process relies on the environment and explains why the disease does not occur every year.

Wet weather during bud-break and leaf emergence favors disease. Low temperatures also slow the leaf development process giving the spores a great window for infection. Therefore cool, wet weather encourages peach leaf curl. Dry, warm weather reduces or prevents disease. Once the leaf tissues mature, they are resistant to the disease. This also explains why secondary leaves formed during the summer when the environment is typically drier and warmer do not get peach leaf curl.

Peach leaf curl is readily controlled with a single spray application made in either late fall after leaf drop or in late winter, before the buds swell. Timing is critical and the buds must be spray before they swell. If they are past this stage or have opened, it is too late for control as infection has already occurred. There is also no treatment available once the symptoms are visible on the leaves. Some fungicides which are effective include: chlorothalonil, Bordeaux mixture, lime sulfur, and fixed coppers. There are no non-chemical controls which have proved effective. If you miss your treatment window and disease develops, thin the fruit to compensate for the loss of leaves. Also, fertilize and water trees to help maintain vigor.
 
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