Occurrence characteristics: The disease is caused by the infection of the fungus, the fungus, the Phytophthora melon. The pathogens overwinter in the soil with mycelium, oospores and chlamydospores. The spring of the next year is spread through wind and rain and irrigation water. The suitable temperature range for the development of pathogens is very wide, between 5 and 37 ° C, and the optimum temperature is 28 to 30 ° C. High humidity is the decisive factor in the pathogenesis. After the thunderstorm, the water in the field cannot be discharged in time to induce the disease. It is very serious in the rainy season, and it is most prone to epidemics after heavy rain. Continuous cropping, poor drainage, excessive watering, application of unsoiled fertile fertilizer, poor ventilation and light transmission fields are more serious. The period from July to August in Zhejiang and the middle and lower reaches of the Yangtze River is the peak period.
　　 Control measures: 1 The implementation of non-melon crop rotation for more than 3 years, using plastic film mulching cultivation, deep sorghum planting, application of fully decomposed organic fertilizer. 2 Seed treatment: seed dressing with new high-fat film before sowing, can keep warm, moisturize, swell, improve seed germination rate, make seedlings strong. Repel underground pests and isolate viral infections. It can also be mixed with a seed coating. 3 Select fields with high dryness and good drainage, pay attention to controlling the number of watering, timely drainage after rain, strengthen ventilation and ventilation, and find the central diseased plants, and remove them in time. 4 chemical control: In the early stage of the disease, the targeted agent is sprayed together with the new high-fat membrane, which can transform high-toxic pesticides into poisoning, poisoning pesticides are low-toxic, and low-toxic pesticides are slightly toxic. Control the volatile and volatile pesticides, prevent the rainwater from scouring, reduce the dosage per acre (half), and improve the control effect (multiple times).
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