Leaf fall is time to treat peach tree

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Last Updated: 
May 31, 2006

CORVALLIS, Ore. – Autumn is time to start treating for peach leaf curl. To do so, apply a sulfur or copper-based fungicide, sometimes called “dormant spray,” three to four times to peach and nectarine trees during the dormant and delayed dormant season.

If peach leaf curl is left unchecked, the disease can reduce fruit production and stunt or kill shoots. Failure to control peach leaf curl disease for three or four years may kill a tree, said Ross Penhallegon, horticulturist for the Oregon State University Extension Service.

“The first treatment should be after leaf fall in autumn,” he said. “This would be a general clean up spray. Then, around Dec. 15 the second spray is needed, both on the east and west side of the Cascades. The third treatment should follow in the late winter, around Feb. 15 for western Oregon and around March 15 for central and eastern Oregon. Most peach owners will spray a fourth time as leaf buds begin to swell and start showing a little green.”

Symptoms of peach leaf curl, which appear in the spring, include curled, distorted and reddened leaves. As the disease proliferates thickened areas on the leaves turn yellowish-gray and velvety. Spores are then ready to spread to healthy leaves. During wet, rainy seasons, the infection is spread over the tree to leaf buds and can become so heavy that the tree is defoliated and will drop fruit that may have been starting to form.

Use a positive action or pressure sprayer, advised Penhallegon.

“Mix-as-you-spray type devices or hose sprayers are not capable of producing effective sprays against peach leaf curl,” he warned.

Two standard sprays are lime sulfur (a mixture of lime and sulfur) and Bordeaux (a mixture of lime and copper sulfate). Always follow the mixing instructions on the label.

If in the spring, when leaves come out, a few infected leaves appear, it is too late - your peach or nectarine tree is infected, Penhallegon pointed out.

“There’s no spray program that can be used when the trees are growing and in tender foliage,” he said. “Once the trees are infected, nothing can be done to stop the infection because it has already happened. If the infection is small, carefully picking each distorted leaf from the tree and putting it in a paper bag immediately will help minimize spores flying to healthy leaves. Destroy the bag and infected leaves you have picked from the tree by burning in an approved manner or throwing the bag into the garbage can. Then, during the following dormant season, treat your tree in late fall and again before leaves bud out.”

For additional information on growing tree fruits and nuts, visit the OSU Extension Service’s online fruit and nut growing publications, including the circular "Managing Diseases and Insects in Home Orchards," (EC 631) or go to: https://catalog.extension.oregonstate.edu/

Local county offices of the OSU Extension Service may have additional information about preventing or controlling diseases and insects in home orchards.

Author: Carol Savonen
Source: Ross Penhallegon