Downy mildew is the most serious disease in grape production in Chongqing. It mainly harms the leaves of grapes. The leaves are translucent at first, and the leaves are unclear, yellowish green oil-immersed spots, and then expanded into yellow to brown polygonal spots. The size of the lesion varies depending on the breed or the condition of the disease. When the humidity is high, the lesions heal, and the white mold layer on the back surface, the lesions finally brown, and the leaves dry and fall off. Downy mildew is usually the most severe in the rainy season from April to June each year .
Prevention and control of grape downy mildew must be taken mainly for prevention, and comprehensive prevention and control measures can be effective. The specific measures are as follows:
Adopt rain-proof cultivation to reduce the humidity of the tree. Grape downy mildew is mainly spread by rainwater, and the grapes are protected by greenhouses during the growing season of the grapes, or covered with plastic scaffolding at the top of the grapevine crowns, so that the grapevines and flowers are protected from the rain, thus preventing and alleviating the grape diseases. occur.
Adopting the "high, wide, thin, vertical" cultivation frame to keep the orchard ventilated and breathable. On the basis of ensuring the yield, the planting density is as low as possible, generally the row spacing is more than 3 meters, the plant spacing is more than 1.5 meters, and less than 111 plants per acre are planted ; the frame type is preferably cultivated by T -frames, and the branching points are high. Generally , it is above 1.3 meters, and the result is more than 80 cm. The branches are distributed wide and flat, receiving sunlight as much as possible and inhibiting the sprouting of new shoots.
Strengthen vineyard management. Deeply digging the drainage ditch, timely draining the water in the ditch, keeping the ditch inside dry, reducing the humidity of the orchard; timely picking the heart, tying the vine and cultivating the weeding, keeping the garden ventilated and transparent; appropriately supplementing the micro-fertilizers such as boron, zinc and calcium, Phosphorus and potassium fertilizer should be added; the ear should be bagged to eliminate the infection of the ear by the pathogen; the organic fertilizer should be applied to the ditch in 9 to 11 months, the organic fertilizer should be applied more than 2 tons per mu , and the weeding and weeding; the leaves and branches should be removed after winter pruning and concentrated. Deeply buried or burned, the clearing of the garden is carried out with 5 waves of sulphur sulphur mixture before the germination of the grapes .
Chemical control. Timely spraying in the early stages, usually in mid to late May to early June and even pesticides or 2, in late August to early September pesticide to spray 2 even substantially achieve the purpose of prevention. 66.8% propineb mu? Valeric propamocarb wettable powders (mold grams, etc.) of 700 to 1000 times, propineb 70% wettable powder (Taisheng) 400 to 600 times, or 25% azoxystrobin Suspension (Amisida) 1000 ~ 2000 times liquid, 80% mancozeb wettable powder (Dasheng, Shan Desheng, etc.) 600 ~ 800 times liquid, have a good control effect. Special attention is paid to the fact that the unsealed orchard is not available with powder. After the fruit is harvested, it can be sprayed once to protect the Bordeaux mixture 200 times.
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