What are the symptoms of grape powdery mildew
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What are the symptoms of grape powdery mildew
Grape powdery mildew is a common disease, although it does not occur every year, once it does, it is difficult to eradicate and clean up, and it can easily cause diseases in grape leaves, petioles, young branches, new buds, young fruits, etc. What are the symptoms at the early stage of the disease, and how to control it effectively? Let's find out.
Symptoms of grape powdery mildew
Early stage is white powder, middle stage is grey-white powder, and later stage is small black spots.
Reasons why powdery mildew is difficult to treat
1. The incubation period of powdery mildew is not easy to detect, and once lesions are seen, it means the disease is in the stage of pathogen reproduction, with wide distribution and multiple levels.
2. Once powdery mildew occurs, it requires multiple consecutive treatments. The pathogen develops resistance, and the control effect decreases.
3. Overdense new shoots, uneven spraying, and areas not hit may cause vibrations, which is conducive to the advantage of the white powder for reinfection.
Prevention and control techniques for grape powdery mildew
1. Young branches should be fixed early, with a reasonable spacing and maintained ventilation.
2. Powdery mildew will take root and sprout when it comes into contact with leaves. Once the incubation period ends, the outbreak is just a matter of opportunity. Early control of the disease is very important.
3. Triazole fungicides (such as flusilazole, triadimefon) and strobilurin fungicides (such as azoxystrobin, pyraclostrobin) are commonly used fungicides in the routine prevention and control of powdery mildew. The toxicity of triazole fungicides should be considered when applying a large amount of water, and resistance to strobilurin fungicides should be noted when used continuously. Bordeaux mixture is very effective in preventing and controlling powdery mildew.
4. During the outbreak of powdery mildew, increase the amount of water sprayed. When spraying, all leaves should be wetted. If it is in a greenhouse, consider whether high humidity may cause other diseases.
5. The pathogen of powdery mildew finds it difficult to infect smooth and thick epidermis, so it is necessary to fertilize reasonably, maintain a robust tree body, apply high-quality foliar fertilizers early, pay special attention to calcium supplementation, and quickly form epidermal cells to ensure the leaves are smooth.
The above is the introduction of grape powdery mildew, in order to control this disease effectively, these technical points can be mastered.
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