It's time for second treatment to prevent peach leaf curl

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Last Updated: 
July 13, 2006

EUGENE - Do you have peach or nectarine trees? January is time for the second treatment of fungicide for peach leaf curl, a fungal disease that commonly afflicts peaches and nectarines.

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

The first application for peach leaf curl should have been after leaf fall in late autumn. A copper-based fungicide (sometimes called "dormant spray") is the standard treatment for peach and nectarine trees.

This second treatment works best if applied when leaf buds begin to swell, but before the silver bud tips turn green, usually in January in the Pacific Northwest.

Use a good positive action or pressure sprayer when applying fungicides for peach leaf curl.

"Mix-as-you-spray type devices or hose sprayers are not capable of producing effective sprays against peach leaf curl," explained Penhallegon.

Two standard sprays are lime sulfur (diluted at the rate of one part lime sulfur per 12 parts water) and Bordeaux. Those compounds with at least 50 percent copper are most effective. Always follow the pesticide label directions, especially for mixing. Each product is usually different.

Symptoms of peach leaf curl appear in the spring - curled, distorted and reddened leaves will appear if your trees are infected. As the disease proliferates, thickened areas on the leaves turn yellowish-gray and velvety. These are spores, ready to spread to healthy leaves.

If you see infected leaves in the spring, it is too late for control this year.

"There's no spray program that can be used when the trees are growing and in tender foliage," he said. "Instead, carefully pick each distorted leaf from the tree and put it in a paper bag immediately to minimize spores flying to healthy leaves. Destroy the bag and infected leaves you have picked from the tree by burning in an approved manner. Then, during the following dormant season, treat your tree in late fall and again before leaves bud out."

During wet springs, peach leaf curl infections can become so heavy that the tree is defoliated and will drop fruit that may have been starting to form.

For more information on "Managing Diseases and Insects in Home Orchards," EC 631, visit our on-line catalog. Our publications and video catalog at: http://extension.oregonstate.edu/catalog/ shows which publications are available on the Web and which can be ordered as printed publications.

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