Peach Leaf Curl
Treatment, identification, and symptoms for Leaf Curl Disease.
Peach leaf curl (Taphrina deformans) is a common fungal disease of peaches, ornamental peaches, and nectarines. It has also been found in apricot trees and occasionally in almond trees. The fungus infects leaves, fruits, blossoms, and shoots. While peach leaf curl is serious, there are ways to protect your trees from it.
Peach Leaf Curl Symptoms
About two weeks after the leaves emerge, they develop yellow or reddish raised areas. They become distorted and puckered as they grow. The raised areas become red or purple. Leaves often fall off of the tree. The leaves that remain will develop a white powder on them. This powder is velvety spores of the fungus, ready to spread when water splashes on them.
Infected shoots are distorted and have small yellowish leaves, or leaves in rosettes (whorled). Flowers are distorted and may drop without forming fruit. The fruit has raised, scaley areas on it.
Because the infected leaves are not able to photosynthesize on the distorted, raised areas, they are costly to the tree. Often if the leaves fall off the tree, it will put out new leaves that are not usually diseased. However, in doing this, they use precious energy needed to grow fruit. If left untreated, peach and nectarine trees will die in two or three years.
The Lifecycle of Peach Leaf Curl
Peach leaf curl is caused by a fungus that infects the bud scales. It forces the leaf, twig, flower, or fruit to produce many more cells in an area than they should. This causes the raised places on the infected part. Cells of the fungus break through the cuticle of the leaf and form structures called asci. Inside these structures, the fungus reproduces sexually to form ascospores. These become the white powder on the leaves and other affected parts of the tree. When water is splashed on the spores, they spread to uninfected tissue and divide into bud-conidia.
The ascospores and bud-conidia survive the summer on the tree. When it gets cool and wet outside in the fall, the ascospores divide into bud-conidia. These bud-conidia continue to divide and eventually form a thin film on the surface of the tree. They overwinter there until spring comes. When water splashes on them, they use the water to travel to new, uninfected tissue.
When Conditions Are Ripe
T. deformans is picky. It can only operate during wet weather that has lasted at least 12.5 hours. Two days of wet weather is better still. The temperature must be below 61F but above 47F. The bud-conidia can only bud when the air is humid (95%). When the temperature becomes 69F, the division stops, and the tree is protected from symptoms of peach leaf curl even if it has fungus on it. Cool-weather favors the fungus as it has longer to reproduce, and the tree’s development slows down. Hot, dry weather with temperatures of 79-87F stop the fungus from developing further.
Managing Peach Leaf Curl
If you see symptoms of peach leaf curl in the spring, it is too late to treat the tree. Cutting affected branches or diseased leaves does not control the disease and can damage your trees. However, integrated pest management (IPM) will control the disease. IPM uses cultural, biological, and chemical controls to deal with pests and diseases like peach leaf curl.
Cultural controls are things you can control about what tree you plant and how you take care of it. They are your first line of defense against pests and diseases. Cultural controls are typically very gentle and do not damage the environment.
There are a few peach varieties that can tolerate leaf curl infection. There are several lists of these cultivars, but Frost, Indian Free, Muir, and Q-1-8 are on most of them. Frost has to receive fungicide treatments in its first 2-3 years but is tolerant after that.
Redhaven peaches and cultivars developed from Redhaven are generally tolerant of the disease. Redskin peaches and cultivars are very susceptible to peach leaf curl.
The only nectarine tree mentioned as tolerant of peach leaf curl is Kreibich.
If many of the leaves have fallen or are affected by peach leaf curl, the peach tree will have less energy to devote to fruit production. It is important to thin the fruit so it does not overtax the tree. Failure to do this can keep the tree from storing enough energy to make it through the winter.
To reduce stress on trees with peach leaf curl, make sure that they get at least one inch a week of water. This counts rain and snow. If it rains or snows less than an inch of water, supplement that to bring the total up to an inch. Be aware that it takes 4-5 inches of wet snow or 10 inches of dry powdery snow to melt into an inch of water.
Fruit trees are heavy feeders. It takes a lot of energy to make fruit. Help your trees by giving them organic fertilizers high in nitrogen. Make sure that any fertilizer you apply is designed for peach trees. Fertilizers for ornamental trees and shrubs do not supply adequate nutrients to fruit trees.
This applies more to pests than to diseases. For example, if a parasitic wasp lays eggs in a caterpillar and the larvae eat it, that is a biological control. There is no recognized biological control for peach leaf curl.
Chemical controls are used as a last resort. These controls can be organic or synthetic. Pyrethrins are an example of organic chemical control. They are compounds found in chrysanthemums.
Treat peach leaf curl with sulfur or copper-based fungicides. You can use them to dust the tree or to spray it. It is generally easier to spray the tree because you can use a sprayer attached to your hose to shoot the spray all over the tree while getting the top of the tree is difficult with the dust. You need to spray the tree until the fungicide is dripping from it. While peach leaf curl is pretty distinctive, sometimes you do not know what is damaging your fruit trees. Bonide® Garden Dust contains sulfur and copper fungicides and pyrethrins. It kills a wide range of fungus and insect pests.
The optimal time to spray the fruit trees is after leaf fall in the autumn. Since the fungus overwinters on the bark and in the bud scales, it is vulnerable to the fungicide. If the trees are badly affected, you can spray again in the late winter or early spring, when the buds swell. Do not use these fungicides in warm weather or after the leaves and flowers come out of the buds. It is too late then.
Make sure you follow all the directions on the label of the product you use. Some fungicides cannot be used in warm weather. Be sure to wear appropriate clothing to apply the product, including long-sleeve shirts, long pants, and closed-toe shoes. You do not want to poison yourself instead of the fungus. Even organic products can make you sick if you use them improperly.
Peach leaf curl is a real threat to peach trees and nectarine. It can be treated with fungicides after leaf drop. Untreated, it will kill the fruit trees in two to three years.
- Select resistant varieties whenever possible.
- Leaf curl can be controlled by applying sulfur or copper-based fungicides that are labeled for use on peaches and nectarines. Spray the entire tree after 90% of the leaves have dropped in the fall and again in the early spring, just before the buds open. For best results, trees should be sprayed to the point of runoff or until they start dripping.
- Containing copper and pyrethrins, Bonide® Garden Dust is a safe, one-step control for many insect attacks and fungal problems. For best results, cover both the tops and undersides of leaves with a thin uniform film or dust. Depending on foliage density, 10 oz will cover 625 sq ft. Repeat applications every 7-10 days, as needed.
- Keep the ground beneath the trees raked up and clean, especially during winter months.
- Prune and destroy infected plant parts as they appear.
- If disease problems are severe, maintain tree health and vigor by cutting back more fruit than normal, watering regularly (avoiding wetting the leaves if possible) and apply an organic fertilizers high in nitrogen.
Liquid Copper Spray
Use as a dormant or growing season spray on fruits, flowers and vegetable crops.$11.95Read more
Sulfur Plant Fungicide
Apply as a spray or dust to treat most diseases on fruits, flowers and vegetables.Read more