Leaf curl

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Curl leaves are plant diseases characterized by leaf curling, and are caused by fungi, genus Taphrina , or viruses, especially the genus Begomovirus of the family > Geminiviridae . One of the most famous species is the peach leaf's curl, caused by the fungus Taphrina deformans , which infects peach trees, nectarines, and almonds. T. deformans is found in the United States, Europe, Asia, Africa, Australia and New Zealand. It was first introduced in America in 1852 and has now spread throughout the country.

Video Leaf curl

Masalah dengan daun curl

Peach leaf curl reduces the number of leaves and fruits produced by peach and nectarine trees. The disease costs US $ 2.5 to 3.0 million per year.

Maps Leaf curl

Causes of curved leaves

The mushrooms of T. deformans cause young leaves to change shape, red blisters, and finally whitish blooms that cover the leaves during infection. This white color is made of asci that penetrates the cuticle cuticle. One ascus consists of eight ascospores that create conidia, which are expelled early in the summer and spread by rain and wind. Mushrooms survive in winter on the surface of host plants, such as on bark or buds. In the winter, rainwater washes the spores into the bud when they explode. Once this happens, there is no effective treatment. In the spring, new leaves are infected by conidia when the leaves appear from the buds. This disease may not occur every year due to variations in temperature and precipitation. In particular, for a successful infection, the fungus requires a cold and wet winter, where rain (not mist or dew) moistens the tree for more than 12.5 hours at temperatures below 16 Â ° C (61 Â ° F).

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Sign of disease

Curl leaves are distinctive and easily visible, and the severity of the signs depends on how early the infection has occurred. Diseased leaves can usually be identified as soon as they emerge from the bud, because the color is red and the shape is bent. As the leaves grow, they become more distorted, and ultimately thicker and chewier than normal leaves. Leaf color changes from normal green to red and purple, until finally whitish blooms cover each leaf. Changes in the skin are less visible, if at all. Fruit may fail to develop from a sick flower, or may be affected, showing a reddish color. Infected leaves fall early. Trees usually produce a rare second leaf, except in a cool, wet spring, because the fungus is not contagious at temperatures that are usually higher in late spring and early summer.

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Disease control

Various methods applied.

• The most effective method is to plant a peach tree on the wall of the house under an overhanging roof, possibly covered by mats during winter, to keep the winter rain from buds before they explode (and accidentally delay the bloom until spring frosts over), until the temperature exceeds 16Ã, Â ° C (61Ã, Â ° F) in the spring, deactivating the fungi.
• Commercially, spraying leaves with fungicides is the most common control method. The toxicity of these fungicides means they are not legally available to non-commercial farmers in some countries. Spraying should be done in winter before budding. If the tree is not sprayed early enough, the treatment is ineffective. Copper-based mixtures (such as Bordeaux mixtures) and lime sulfur are the two commonly used fungicides.
• Peach cultivars can be planted that exhibit resistance to peach leaves, or at least rapidly regenerate, such as Peach 'Benedicte'. No cultivars of the same nectarine are unknown.

If a plant seems to have leaf curling signs in a given year, the disease will take its course, but precautions can be taken to maintain the tree or maximize the yield: for example, treating it with nitrogen and excess water to minimize stress on the plant. tree; apply greasebands around the stem to protect against insect attacks; and thins the fruit. It is not clear whether removal of infected leaves from the tree is beneficial. Removing infected leaves and fruits after falling to the ground is sometimes also advised but exaggerated if, in the following winter, fungicides or rain protection is applied.

src: agropedia.iitk.ac.in

5 year plan USDA 1992

This USDA document illustrates a 5-year plan beginning in 1992 to reduce whiteflies.

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References

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External links

• Fungorum Index
• USDA ARS Fungal Database
• Royal Horticultural Society - Peach Leaf Curl
• Peach Leaves Treatment

Source of the article : Wikipedia