1. The cause of the disease: The pathogens overwinter in the soil or field grass with conidia. When the conditions in the next year are suitable, the conidia released from the organs spread to the watermelon leaves through wind and rain, and the pathogens germinate and invade. Later, it causes initial infection and reinfection. Watermelon plants are easily induced by freezing or lack of fertilizer and peeling scratches during transportation and storage. Continuous cropping land, fields with a large amount of pathogenic bacteria in the previous crops, low-lying water, poor drainage, heavy soil, and soil acid fields are severely affected; excessive nitrogen fertilizer is applied, dense cultivation, and canopy between plants and rows , Plots with poor ventilation and light transmission are prone to disease.

2. Control methods 1. Agricultural control (1) Carry out 2-3 years of crop rotation with non-cucurbit crops, and apply compost made of fermented bacteria or fully decomposed organic fertilizer. (2) High-border cultivation, mulching with plastic film, and strengthening drainage in the rainy season. 2. Chemical control (1) Dress the seeds with 50% thiram wettable powder with 0.3% of the seed weight. (2) Spraying at the initial stage of the disease: 50% thiophanate methyl, 800 times liquid of sulfur suspension, 400-500 times liquid of 36% thiophanate methyl suspension, 77% copper hydroxide (can be killed) wettability Particle powder 500 times liquid, 75% chlorothalonil (Dakoning) wettable powder 600 times liquid, 50%? Frightened, Ye 螘蛩? Sterilization King) Water-soluble powder 1000 times liquid or Huimanfeng multi-element active liquid fertilizer, 320ml per mu, diluted 500-600 times liquid, also once every 7 days, can use Fufengbao II 1000 times liquid, every 7 days , Spray 2-3 times. Stop medication 7 days before harvest.