Cucumber powdery mildew symptoms
Powdery mildew mainly infects leaves, stems and petioles, and generally does not harm melons. At the beginning of the disease, there were nearly round white star-shaped small pink spots on the front and back of the leaves, which spread to the surrounding and spread into pieces. In severe cases, the white powder covered the whole leaves. In the later stage, the white spot is changed to grayish white due to the mycelium, and many small black spots are produced. The leaves gradually become grayish white to grayish yellow, and the texture becomes brittle. Plants can be harmed from the seedling stage, but there are more cases in the middle and late stages.
Cucumber powdery mildew transmission path and disease conditions
The pathogens overwinter with the diseased bodies, and they can also overwinter on the melons grown in the greenhouse. The greenhouses of the melon crops are the main wintering place for the bacteria. The germs spread by air and rain and invade directly from the leaves. The suitable temperature for the generation of conidia by the pathogen is 15-30 ° C, and the relative humidity is 80%. The sheds and fields are dry after flooding or rain, and the incidence of powdery mildew is heavy, especially high temperature and drought. When alternating with high temperature and high humidity, or continuous sultry, powdery mildew is very popular. Cucumber cultivation is too dense, lack of light, extensive management, long plants, premature aging, etc. will promote powdery mildew.
Cucumber powdery mildew prevention and treatment method
1. Different varieties of resistant varieties have different resistance to powdery mildew, and it is necessary to choose disease-resistant and disease-resistant varieties according to local conditions in production practice. Such as Lu Cucumber No. 4, Lu Cucumber No. 10, Jinan Mia, Jinyan No. 4, Jinchun No. 3, Jinza No. 1, Jinza No. 2, Xiafeng No. 1, etc.
2. Greenhouse greenhouse disinfection greenhouse greenhouses about 10 days before planting, after the mulch film cover shed, sealed, so that the chamber temperature is raised as much as possible above 45 °C for disinfection. The higher the temperature and the longer the time, the better the effect. It can also be ignited with 2-3 kilograms of sulfur powder per acre greenhouse with 5-6 kilograms of sawdust, or 1 kilogram of bacteriological clearing agent per acre. When fumigation, the greenhouse should be sealed.
3, cultivation and control per mu of fully-fertilized high-quality ring fertilizer 5000-7500 kg, phosphorus and potassium fertilizer 25-30 kg as a base fertilizer can also be applied to some chicken manure, large manure, grass ash and so on. The melon period is divided into 3-4 times to apply quick-acting nitrogen fertilizer and topdressing foliar fertilizer. Cucumber cultivation in greenhouses should also carry out carbon dioxide fertilization to prevent premature senescence of plants, so as to improve the disease resistance of plants; cultivation methods should be covered with sorghum cultivation and plastic film to protect roots; timely tying or hanging, cultivating and weeding, removing leaves and bottom of dried yellow leaves Leaves, brought out of the field or greenhouse outside the greenhouse; appropriate control of watering, open field cucumber should be timely ploughing, do a good job of drainage after rain, reduce the relative humidity in the field. Greenhouses should increase lighting and ventilation as much as possible.
4. In the early stage of biological control of powdery mildew, spray 2% agricultural anti-120 water agent 200 times liquid or 2% agricultural anti-BO-10 water agent 200 times liquid, spray once every 4-5 days, even spray 2-3 times.
5, the beginning of physical control began to spray 27% high-fat film emulsion 80-100 times solution, spray 5-7 days, even spray 3-4 times to form a protective film on the foliage to prevent the invasion of pathogens.
6. In the early stage of chemical control, 40% Fuxing emulsifiable concentrate 8000 times solution, 75% chlorothalonil WP 600 times solution, 40% poly-sulfur suspension 500-600 times solution, 40% thiophanate-methyl -Sulphur suspension 800 times solution, 50% sulfur suspension agent 250-300 times solution, 30% DT suspension agent 400-500 times solution, 50% methyl thiophanate wettable powder 800-1000 times liquid spray control, 7-10 Spray once a day, even spray 2-3 times.
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