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Pests in Gardens and Landscapes: Quick Tips

Foliage damaged by peach leaf curl.

Reddened and puckered leaves caused by peach leaf curl.

Peach leaf curl is a fungal disease that affects only peach and nectarine trees. Distorted, reddened foliage in spring is a distinctive symptom of peach leaf curl. New leaves and shoots thicken, pucker, and may later die and fall off. If you allow an infection to go untreated for several years, it can lead to tree decline. To prevent peach leaf curl, treat susceptible trees with a preventive fungicide every year after leaves fall. Treating after symptoms appear won?t be effective. When planting, consider tree varieties resistant to the disease.

Look for symptoms in spring.

• New leaves and shoots redden and pucker. Leaves may yellow or be covered with powdery gray spores; leaves might also 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 (79° to 87°F).
• Symptoms won’t appear later in the season, although spores that can infect next year’s growth may remain.

What about pesticides?

• The safest, effective fungicides available for backyard trees are copper soap (copper octanoate) or copper ammonium, a fixed copper fungicide.
• Apply either of these copper products with 1% horticultural oil to increase effectiveness.
• Bordeaux mixture is a home-made copper sulfate and lime mixture that must be carefully mixed up just prior to treatment. However, the raw materials are difficult to find.
• The synthetic fungicide chlorothalonil is also effective.

Treat trees with a fungicide in late fall and winter.

• The fungal spores that cause the disease spend the winter on twigs and buds and germinate in the spring. For effective control, treat trees just after leaves have fallen, usually late November or December.
• A second application in late winter before buds swell can be considered, especially in areas with high rainfall or during wet winters.
• Don’t apply fungicides during the growing season because they won’t be effective.

Make fungicide applications effective and safe.

• All peach leaf curl fungicides have environmental and health risks. Wear protective clothing and follow label directions to stop drift or runoff.
• When you spray, thoroughly cover all branches and twigs until dripping to ensure all spores are killed.
• 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 runoff.

Minimize the use of pesticides that pollute our waterways. Use nonchemical alternatives or less toxic pesticide products whenever possible. Read product labels carefully and follow instructions on proper use, storage, and disposal.