- Author: Lauren Fordyce
Spring is just around the corner and many types of fruit trees are starting to develop their leaves. If you are growing peaches or nectarines and are now seeing symptoms of peach leaf curl on new leaves, unfortunately it's too late to manage the disease.
According to University of California research, peach leaf curl can only be effectively managed during the fall and winter, after leaves have dropped but before buds swell in spring. After bud break (when new buds begin to open), you may notice symptoms on new leaves but at this point, there are no effective controls. Pesticides used against peach leaf curl prevent the disease as opposed to curing it. Currently there are no verified curative methods for controlling peach leaf curl during the growing season.
Peach leaf curl is a fungal disease that primarily affects peach and nectarine trees. Its spores overwinter on the twigs and flower buds, and germinate in the spring causing distorted, reddened leaves. If left untreated for several years, trees can decline and may need to be removed. In some cases, peach leaf curl can also affect fruit quality.
During the dormant season (fall and winter), spray affected trees with a fungicide containing the active ingredients copper or chlorothalonil. These active ingredients can be used alternately to limit copper buildup in the soil. Horticultural oils and other fungicides have not proven to be effective against peach leaf curl. Always read the label of the pesticide product you want to use and verify that it is labeled to treat the pest you are dealing with. To learn more about pesticide active ingredients and their potential toxicity, see the UC IPM Pesticide Active Ingredient Database.
To learn more about this disease and its management, visit the UC IPM Pest Notes: Peach Leaf Curl.
Peach leaf curl is a fungal disease that only affects peach and nectarine trees. The fungus causes distorted, reddened leaves to appear on the tree in the spring. While many peach and nectarine trees don't begin to show obvious symptoms of peach leaf curl until the spring, the time to manage the disease is in late fall and winter.
If left untreated for several years, trees can decline and need to be removed. In some cases, peach leaf curl can affect the quality of fruit too.
To effectively control peach leaf curl, spray an appropriate fungicide in the fall or winter, after leaf drop but before flower buds swell in the spring. The fungal spores overwinter on peach and nectarine twigs and flower buds. If left untreated, the spores will germinate in the spring, especially in years with heavy rainfall. In Northern California you can usually treat trees starting in late November. In Southern California you can usually start in early January. A single treatment while the tree is dormant is generally advisable, but in areas that get a lot of rainfall, you may want to spray again later in the dormant season.
Numerous copper-based fungicides are available to effectively treat peach leaf curl when used according to label instructions. Always read the product label before buying or using a pesticide. Use only the rate listed on the label to avoid fungicide resistance and avoid making applications before it rains.
For more management information, see the UC IPM Pest Notes: Peach Leaf Curl and Pesticides: Safe and Effective Use in the Home and Landscape.
If the new leaves of your peach or nectarine tree become reddish, puckered and severely distorted, chances are that peach leaf curl is the culprit. This disease is caused by the fungus Taphrina deformans and is one of the most common disease problems for backyard peach and nectarine trees here in Butte County. In addition to disfiguring leaves, leaf curl can affect the blossoms, stems and fruit of infected trees. If it is severe enough, leaf curl can significantly weaken a tree and reduce fruit production. Leaf- curl-affected leaves fall off in spring, exposing the main limbs to sunburn injury. And sunburn injury facilitates flatheaded borer attacks, which often result in limb dieback.
The best way to avoid leaf curl is to grow resistant varieties of peaches and nectarines, so if you are planning to buy fruit trees, keep this in mind. Resistant peach varieties include Frost, Indian Free, Muir and Q-1-8. Although the Frost peach variety is very resistant to leaf curl, it must receive fungicide applications in its first two to three years of growth. Red Haven peach and most of the varieties derived from it are rated “tolerant” to leaf curl. On the other hand, Redskin peach and its cultivars are rated “susceptible to highly susceptible” to the disease. Kreibich is a nectarine variety that is resistant to leaf curl.
The most common fungicides available to the home gardener contain fixed copper. The active ingredient, copper, is listed as “metallic copper equivalent,” or MCE. The higher the MCE, the more effective the product will be. Thorough coverage (by spraying the trees until they are dripping) is essential for disease control. Be aware that repeated use of copper products can result in the buildup of copper in the soil, where it may become toxic to soil organisms. The synthetic fungicide, chlorothalonil, is the only non-copper fungicide available for managing leaf curl on backyard trees. When using pesticides, always read and follow the label for usage, rates, toxicity and proper disposal. Proper protective clothing and gear (including goggles) should be used when handling any pesticides.
When the symptoms of peach leaf curl appear on a tree in the spring, nothing can be done to control the disease at that time. Removing diseased leaves or shoots does not control the disease. If your tree has leaf curl now, be sure to treat it next winter to prevent more serious problems the following spring.
For more detailed information on this topic, see the University of California Integrated Pest Management Pestnote #7426: Peach Leaf Curl Management Guidelines--UC IPM (ucanr.edu).
JOB OPPORTUNITY: UC Cooperative Extension has an opening for an individual who can provide administrative and program oversight to the Master Gardener Program, plus technical and educational training to support the creation and maintenance of gardening programs with UC CalFresh Nutrition Education Program clientele in Butte County. For more information and to apply for the Garden Education Coordinator position visit Jobs - Division of Agriculture and Natural Resources (ucanr.edu).
- Author: Ed Perry
- Editor: Anne Schellman
The peach leaf curl fungus is spread by tiny spores which are produced on infected leaves and blown about by wind. As leaves begin to emerge in the spring, the spores are washed onto them, and infection begins. If the weather remains cool and wet, young leaves will be continually infected. Throughout the winter, while the tree is dormant, the spores lie exposed on limbs, twigs and buds. It is during this period that the disease can be controlled with fungicide sprays. In the dry, hot weather of late spring and early summer, the disease stops spreading.
Spraying now during the dormant season helps prevent peach leaf curl in spring. Several products are generally effective in controlling peach leaf curl and are readily available at nurseries and garden stores. These include products containing basic copper sulfate. Make sure to do a thorough job of covering every bit of the tree with the spray.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
[From the UC IPM blog Pests in the Urban Landscape]
1. Aphids
These insects may be small, but they can quickly build up large populations. With many different species in California that feed on vegetables, flowers, fruit trees, and woody ornamentals, aphids are a common sight in landscapes and gardens. Year after year, aphids continue to hold the top spot. Learn more about aphids and their management in Pest Notes: Aphids.
2. Fungus Gnats
3. Thrips
Another tiny insect sometimes found on houseplants, thrips are slender insects about the size and shape of a dash printed in a newspaper. They suck out the cell contents, leaving a discolored speckling on leaves or stunting plant growth. For more about thrips monitoring and management, visit our Pest Notes: Thrips.
4. Mealybugs
If you've found soft, oval insects that are white in color with wax filaments on your indoor or outdoor plants, it is likely you have mealybugs. These wingless insects are often found in clustered colonies. In yards and gardens, handpicking, pruning, or high-pressure water sprays can reduce populations. For small infestations indoors, spot treatments may help reduce populations. For houseplants with severe infestations, consider disposing of the plant. Find additional information in Pest Notes: Mealybugs.
5. Carpet Beetles
6. Peach Leaf Curl
Peach leaf curl can affect the blossoms, fruit, leaves, and shoots of peach and nectarine trees. The symptoms of the disease first appear in spring, when distorted red foliage emerges. However, focus management for nonresistant varieties in the late fall and early winter, after leaves drop. Read more about this disease in our Pest Notes: Peach Leaf Curl.
7. Clothes Moths
New to the top ten list this year were clothes moths. These pests tend to hide when disturbed, so you may not realize you have an infestation until after the moths have already damaged fabric, fur, or feathered items. Some clothes moths make webs while others are casemaking moths. Regularly monitoring and cleaning clothing and storage areas can help prevent or reduce infestations. Find more identification and management information from Pest Notes: Clothes Moths.
8. Springtails
9. Whiteflies
Whiteflies are not actual flies but are tiny insects that are often found on the underside of leaves, feeding on the phloem of many different plants. Certain species can cause significant loss in vegetable gardens; other species found in fruit trees are less damaging. Both adult and immature whiteflies also attack houseplants. Management information can be found in Pest Notes: Whiteflies.
10. Scales
Scales are small, legless insects that look like tiny scabs on the stems, leaves, or fruit of plants. While some scale species can weaken a plant when abundant, other species do not appear to damage plants at all. Think you have a problem with these insects? Visit our Pest Notes: Scales for identification and management options.
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