How to Manage Pests

Peach leaf curl is a fungal disease that only affects peach and nectarine trees. Distorted, reddened foliage on peach or nectarine trees in the spring is a distinctive symptom. Newly emerging leaves and shoots thicken and pucker, and may later die and fall off. A leaf curl infection that continues untreated over several years will contribute to a tree’s decline. To prevent peach leaf curl, treat peach and nectarine trees with a fungicide every year after leaves fall. Treatment in spring after symptoms appear will not be effective.

• First symptoms of reddening and puckering occur on new leaves and shoots in spring. Leaves may yellow, become covered with powdery gray spores, and drop.
• Cool, wet spring weather prolongs disease development.
• A second set of normal leaves will replace fallen leaves and tree growth will appear normal after weather turns dry and warm (79º to 87ºF), although spores that can infect next year’s growth may remain.
• Symptoms will not be seen later in the season.

• Treat just after leaves have fallen, usually late November.
• In wet climates or during a wet winter, consider a second application in late winter or early spring just before buds swell. Although a single treatment is sufficient in most areas, this second application may be advisable in areas or years with high rainfall.
• Don’t apply fungicides during the growing season because they will not be effective.

• Copper-based fungicides such as tribasic copper sulfate or cupric hydroxide (also known as fixed copper) are easiest to use and are most effective if applied with oil.
• Bordeaux mixture is a copper sulfate and lime mixture that should be carefully prepared just prior to treatment. See Pest Notes: Bordeaux Mixture for a recipe.
• Lime sulfur, although very effective, must be handled carefully. It can cause injury to eyes and skin.
• The synthetic fungicide chlorothalonil is also effective.

• The fungal spores that cause the disease germinate in the spring and spend the winter on twigs and buds. When you spray a fungicide, thoroughly cover all branches and twigs so all spores are killed.
• All peach leaf curl fungicides have environmental and health risks. Wear protective clothing and follow label directions to stop drift or runoff.
• After many years of use, copper ions from copper-based fungicides can accumulate in soil. This can harm soil microorganisms, and through runoff, aquatic organisms. Take care when using these materials to avoid excessive dripping.

What you use in your landscape affects our rivers and oceans!