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).
If you have peach or nectarine trees, winter is the time to spray them to prevent peach leaf curl.
The best way to avoid leaf curl is to use resistant varieties of peaches and nectarines. 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 its first two to three years of growth. Redhaven 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 be 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.
For more detailed information on this topic, see the University of California Integrated Pest Management (UC IPM) Pestnote #7426, Peach Leaf Curl.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area, visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu (preferred) or call (530) 538-7201.
By Brent McGhie, Butte County Master Gardener, November 13, 2015
Peach leaf curl is a fungal disease affecting only peaches and nectarines. Its distinctive symptoms include the curling, reddening, and thickening of leaves as they open in the spring. Diseased leaves will die and fall off, but are usually replaced by new, healthy leaves once the weather becomes warmer and drier. Still, if this disease is left untreated, defoliation can lead to sunburned limbs followed by borer attacks. Over several years, affected trees may decline and fruit production can be reduced.
To prevent peach leaf curl, trees must be sprayed with a fungicide after their leaves have dropped and they are dormant. This is usually in late November, or December. If it is a particularly wet winter, a second application of fungicide can be made in early spring, just as buds begin to swell. An easy way to remember is to target spraying for “curly leaf” at Thanksgiving and again at Dr. Martin Luther King's Birthday. Once peach leaf curl symptoms appear (when trees leaf out in the spring) it's too late for anything to be done to stop the disease. Spraying after symptoms show up is ineffective and removing diseased leaves or shoots will not remedy the problem.
For the home gardener, there are two treatment options. The most effective is the fungicide chlorothalonil (commercially sold as Daconil, Fung-onil, and Ortho Garden Disease Control, among other brands). However, it must be handled with care because it is listed as a likely carcinogen and can cause skin and eye irritation if handled improperly or if protective clothing and equipment (gloves and goggles) aren't worn. A somewhat less effective treatment is copper ammonium complex sold as Liqui-Cop (a Monterey Lawn and Garden product), or Kop R Spray Concentrate (a Lilly Miller brand). It can be made more effective by applying it with 1% horticultural spray oil in the spray solution. As is the case with all garden chemicals, be certain to read and follow all cautions and instructions on the label.
If you prefer not to spray, you can avoid leaf curl by planting resistant varieties of peaches and nectarines. 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. Kreibich is a nectarine variety that is resistant to leaf curl.
Citrus blast and brown rot are diseases that attack citrus trees. Although citrus blast is caused by a bacterium that attacks leaves and shoots and brown rot is a fungal disease that causes fruit to rot and turn brown, both of these diseases can be controlled by spraying with the same copper ammonium complex used to treat peach leaf curl.
When heavy rain, high winds and low temperatures occur together, conditions are optimal for citrus blast, especially on the windward side of the tree. Leaves affected by this disease have a withered, bleached appearance, as if “blasted” by a blow torch. Diseased leaves and twigs will die and occasionally a larger branch can die back. In most cases, fruit production is reduced and the appearance of the tree is adversely affected.
As with peach leaf curl, once the symptoms of brown rot or citrus blast appear, it's too late to treat them. Both of these diseases are associated with cool, wet conditions, so the best time to spray is before the winter rains begin if you wish to protect navel oranges from brown rot, usually mid-October. A second spraying in mid-December and a third in mid-January has been shown to be effective in reducing the severity of citrus blast. For maximum protection, all parts of the tree should be thoroughly coated. The rough texture of mandarin skins can make it difficult to wash spray residue off of fruit. If this residue is not acceptable, an option is to delay spraying until immediately after fruit has been harvested.
By Brent McGhie, Butte County Master Gardener, December 13, 2013
Peach leaf curl, citrus blast and brown rot of citrus fruit are diseases common in Butte County. Fortunately, all three can be prevented or reduced with fall and winter spraying.
Peach leaf curl is a fungal disease affecting only peaches and nectarines. Its distinctive symptoms include the curling, reddening, and thickening of leaves as they open in the spring. Diseased leaves will die and fall off, but are usually replaced by new, healthy leaves once the weather becomes warmer and drier. Still, if this disease is left untreated, defoliation can lead to sunburned limbs followed by borer attacks. Over several years, affected trees may decline and fruit production can be reduced.
To prevent peach leaf curl, trees must be sprayed with a fungicide after their leaves have dropped and they are dormant. This is usually in late November, or December. If it is a particularly wet winter, a second application of fungicide can be made in early spring, just as buds begin to swell. An easy way to remember is to target spraying for “curly leaf” at Thanksgiving and again at Dr. Martin Luther King’s Birthday. Once peach leaf curl symptoms appear (when trees leaf out in the spring) it’s too late for anything to be done to stop the disease. Spraying after symptoms show up is ineffective and removing diseased leaves or shoots will not remedy the problem.
For the home gardener, there are two treatment options. The most effective is the fungicide chlorothalonil (commercially sold as Daconil, Fung-onil, and Ortho Garden Disease Control, among other brands). However, it must be handled with care because it is listed as a likely carcinogen and can cause skin and eye irritation if handled improperly or if protective clothing and equipment (gloves and goggles) aren’t worn. A somewhat less effective treatment is copper ammonium complex sold as Liqui-Cop (a Monterey Lawn and Garden product), or Kop R Spray Concentrate (a Lilly Miller brand). It can be made more effective by applying it with 1% horticultural spray oil in the spray solution. As is the case with all garden chemicals, be certain to read and follow all cautions and instructions on the label.
If you prefer not to spray, you can avoid leaf curl by planting resistant varieties of peaches and nectarines. 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. Kreibich is a nectarine variety that is resistant to leaf curl.
Citrus blast damage
Citrus blast and brown rot are diseases that attack citrus trees. Although citrus blast is caused by a bacterium that attacks leaves and shoots and brown rot is a fungal disease that causes fruit to rot and turn brown, both of these diseases can be controlled by spraying with the same copper ammonium complex used to treat peach leaf curl.
When heavy rain, high winds and low temperatures occur together, conditions are optimal for citrus blast, especially on the windward side of the tree. Leaves affected by this disease have a withered, bleached appearance, as if “blasted” by a blow torch. Diseased leaves and twigs will die and occasionally a larger branch can die back. In most cases, fruit production is reduced and the appearance of the tree is adversely affected.
As with peach leaf curl, once the symptoms of brown rot or citrus blast appear, it’s too late to treat them. Both of these diseases are associated with cool, wet conditions, so the best time to spray is before the winter rains begin if you wish to protect navel organges from brown rot, usually mid-October. A second spraying in mid-December and a third in mid-January has been shown to be effective in reducing the severity of citrus blast. For maximum protection, all parts of the tree should be thoroughly coated. The rough texture of mandarin skins can make it difficult to wash spray residue off of fruit. If this residue is not acceptable, an option is to delay spraying until immediately after fruit has been harvested.
Brown rot damage and droplets of gum (left) and brown rot on peach (right)
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