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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.
Look for leaf curl symptoms in spring.
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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 trees with a fungicide in late fall to prevent leaf curl.
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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.
Choose effective fungicides.
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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.
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Take care to make fungicide applications effective and safe.
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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.
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.
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