First, the damage characteristics Bitter gourd powdery mildew mainly infects the leaves, but also can damage the stem and petiole, generally does not harm the fruit. In the early stage of leaf damage, white round spots were formed on the front or back of the leaves, and then they gradually spread to the surrounding area and connect into a piece to form a large spot with irregular edges. The diseased leaves gradually became yellow and brittle but generally did not fall off. In severe cases, the entire leaf and vine were covered with white powder, and then the top of the yellow leaf curled, the plants declined, the larvae deformed, and the yield and quality were significantly reduced. When the fall is dry, many black spots appear on the white mold. Bitter powdery mildew is caused by obligate parasitic melon monocystis. The pathogen also infects many melon crops. A large amount of powdery spores are produced on the lesions and spread with the airflow. Generally in high temperature and dry weather is conducive to the spread of germs, humidity is more suitable for disease, but the leaves have water droplets or rainy days when the humidity is too saturated when the spores easily swell and rupture. Therefore, the damage is severe under the conditions of alternating wet and dry conditions. In greenhouses, high temperature, high humidity, lack of light, and no rain, are conducive to disease epidemics. Second, the prevention and treatment of opinion due to the early occurrence of bitter gourd powdery mildew, the incidence of heavy, the majority of melon farmers to strengthen the field inspection (including bitter gourd, melon melon - long melon, cucumber and other melons), timely prevention and treatment. 1, increase the application of phosphorus and potassium fertilizer, not partial nitrogen fertilizer to prevent plant growth and defermentation of premature aging. There is no accumulation of water in the field, and the lower disease and yellow leaves are promptly removed to facilitate ventilation. Prolong the ventilation time of the greenhouse under the condition of ensuring the temperature. 2, medication should be mastered in the initial period, the incidence of the field that field control. Old wards should be sprayed for prevention. 50% of Tribulus terrestris has been used for field plots 3000 to 4000 times, or 12.5% ​​for cymoconazole, 1500 to 2000 times; for non-pathogenic plots, 50% Tribectus 5000 times, or 40% Dupont, 6000 times, or agronomic resistance 120 200 times, or 10% of the world height 1500 times prevention. About seven days or so prevention and control, continuous control of 2 or 3 times. Tribembe is effective against powdery mildew and has good therapeutic effects. It can also prolong the harvesting period of crops. However, it cannot be used more than twice per season. Otherwise, it is easy to produce drug resistance.
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