First, black rot 1, symptoms and damage characteristics. The typical symptom of the disease is the appearance of "V" shaped lesions from small to large. The cotyledons of the affected seedlings were water-stained and quickly died or spread to true leaves. In the epidemic situation, the leaf margins are infested in many places, resulting in the dead leaves of the whole plant or the partial or complete decay of the outer leaves. When the plants are dry, the spots are dry or perforated. The disease mainly occurs in the fall or in high temperature and rainy conditions. It is sown too early and in the case of many pests, the disease is heavier. The pathogens invade through seedling cotyledon stomata, adult plant leaf margin water holes or wounds, etc., and are transmitted through rainwater and insects. 2, control methods. (1) Selection of disease-resistant varieties. (2) Rotation is carried out for two to three years with non-cruciferous vegetables. The former is best used for onions and garlic. (3) Seed disinfection. Seed soaking in warm water at 50-55°C for 20 minutes, or soaked in a 1:200 formalin solution for 20 minutes, or with 40% thiram. (4) timely sowing, reduce the number of field operations, do not operate the leaves, not too late. (5) Timely control of pests. (6) Chemical control. At the beginning of the disease, 72% of agricultural streptomycin soluble powder was sprayed at 4000 times, or 77% could kill WP 500 times, once for 7-10 days, even for 3 times. Second, virus disease 1, symptoms and damage characteristics. The typical symptom of the disease is chlorotic mottled leaves. The leaves of the affected seedlings had chlorotic near-round spots, and the heart veins were slightly mosaic. The color of the later leaves became pale or became dark green and green mottled, and the mosaic leaves and leaves shrank. In severe cases, the leaves were deformed, shrunken, and the plants were short and sometimes dead. The disease is spread by budworms and other insects. Therefore, the occurrence of aphids is serious and the disease is serious. 2, control methods. (1) Selection of antiviral diseases. (2) A reasonable rotation, and the diseased plants were found to be removed in a timely manner. (3) timely sowing, shade nursery. (4) Control locusts in time for seedlings. (5) Strengthen water management to prevent plants from feeling sick due to high temperature. (6) Chemical control. At the beginning of the onset, spray 20% virus A wettable powder 500 times, or plant double action booster 800-1000 times, or 1.5% plant disease emulsion 1000 times, or 83 booster 100 times, 7-10 Once a day, a total of 2-3 times. III. Downy mildew 1. Symptoms: The typical symptom of the disease is irregular polygonal yellow spot caused by limitation of veins in the lower leaves, and white moldy leaves on the leaves or leaves when the humidity is high. In severe cases, the conjunctiva becomes dark brown and dry. The disease is prone to occur under high temperature, high humidity or low temperature and high humidity environment. 2, control methods. (1) Strengthen field management, timely release air temperature, dehumidification and seedling time, and time seedlings, and reasonably dense planting. (2) Chemical control. In the early stage of disease, spray 75% chlorothalonil 500 times, 58% lepidomer 500 times, or 72.2% pliconic agent 600 times, once a day for 7 days, and prevent 3 times. Fourth, soft rot disease 1, symptoms. The typical symptom of the disease is that the outside of the plant is wilted during the day, recovers sooner or later, the outer leaves do not recover, and the diseased part rots and stinks. The disease is prone to occur under high temperature and high humidity conditions. It occurs on the bulbs or at the base of the stem during the harvest period. It initially appears translucent water stains, and then turns grayish-grayish brown. The epidermis sinks, white mucus accumulates, and the interior decays and stinks. 2, control methods. (1) Sorghum sorghum cultivation, furrow irrigation or sprinkler irrigation, flood irrigation is strictly prohibited. (2) Prevent pests and avoid man-made wounds. (3) Chemical control, spraying streptomycin sulfate or 72% of agricultural streptomycin soluble powder 3000-4000 times, or neophytin 4000 times, 10 times a day, a total of 2-3 days.
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