Greenhouse cucumber black spot disease occurs widely, and it is also a domestic phytosanitary object, which is serious. In recent years, there has been a trend of development. In addition to harming cucumbers, it is also inoculated with zucchini, pumpkin, watermelon, melon, etc., and attention should be paid to strengthening prevention and control. I. Symptoms Characteristics Seedlings are infected, yellow-white round spots appear on the cotyledons, and the whole leaves are dry after development; stems are infected with water-soaked dark green fusiform spots, concave cracks, black mold layer when humidity is high; tendrils Then it turns brown and rot; the growth point is infected for 2 to 3 days, and the heartless seedlings are rotted into bald piles; the diseased leaves begin to produce chlorotic spots, which are nearly round, gradually enlarged and quickly dry, forming a round or nearly round yellow-white large The lesions, after the perforation of the lesion leaves a star-like edge, the periorbital leaves shrink; the dark green depression on the melon strip, the surface grows black mold layer, the lesion appears as a scab, stops growing, forming a deformed melon. Second, the optimal temperature for occurrence of conditions is 20 ° C ~ 22 ° C, relative humidity of 90% or more. Therefore, even cloudy days, insufficient light, plant stagnation, excessive humidity, long-term heavy sputum and sowing of diseased seeds are important conditions for the onset of disease. Third, prevention and treatment methods Rotation. Rotating with non-cucurbitaceae vegetables for 2 to 3 years. 2. Use disease-free seeds and seed treatment. In addition to selecting resistant varieties, it is also necessary to use disease-free seeds. The diseased seeds need to be disinfected. They can be soaked in warm water at 50 °C for 30 minutes, and then taken out and cooled to germination. It can also be seeded with 50% carbendazim or captan WP which is 0.4% by weight of the seed. 3. The greenhouse uses sulphur powder to smoke. Before planting or nursery in the greenhouse, turn the ground, use 2.4 grams of sulfur per cubic meter of space, add 4.5 grams of sawdust and mix well, and then ignite the closed smoke for 1 night. After 7 to 10 days, seedlings or colonization can effectively kill the bacteria. 4. Strengthen greenhouse management to prevent disease from occurring. In the production period, flooding of large water is strictly forbidden, and dehumidification should be carried out by means of warming and dehumidification and high-temperature air release. The specific method is: after the scorpion is exposed every morning, the humidity in the shed can reach 90% to 100%. At this time, ventilation and moisture can not be taken. One of the reasons is that the greenhouse cucumber growth period must be 28 ° C ~ 33 ° C every morning is the most suitable high-yield temperature, the early release of low temperature is not conducive to high yield of cucumber; the second reason is that the indoor humidity can be reduced by 1 ° C 2% to 3%. Therefore, in the morning, when the temperature is low and the air is dehumidified, it is worse than the effect of warming and dehumidifying. Therefore, the correct way is to not release the wind immediately after the morning is revealed. It should be to close all the air outlets and let them warm up to 33 °C ~ 35 °C and then suddenly open the top air outlet for air release and dehumidification. However, when the temperature drops to 30 °C, the air vent is closed again, and when it exceeds 33 °C, the air is released. Every morning, 2 to 3 times of high temperature release, and in the afternoon, the temperature is reduced to 25 ° C ~ 28 ° C. This will greatly reduce the humidity, especially the nighttime humidity, and effectively control the occurrence of black spot disease and various diseases. 5. Drug control. When a diseased plant is found in the shed (the diseased seedling should be removed in time), 45% chlorothalonil aerosol should be used immediately for 1 time, and 40% DuPont Fuxing 8000 times spray or 50% chlorhexidine WP can be used. 1000 times liquid leaf spray, once every 7 days, pay attention to the use of drugs can receive better results (Yongqing County Vegetable Administration 065600) From: "Hebei Science and Technology News"
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