In recent years, watermelon in protected areas in Jiangsu has developed rapidly. Due to the overcast and rainy weather during the growth period, it has provided favorable conditions for the occurrence of watermelon blight, and the onset has increased year by year.
Watermelon blight mainly harms stem vines and also damages leaves and fruits. Infested with melon vines, many of them develop on the ground near the stem nodes. Dark greenish oily streaks appear first, and amber gums are secreted. When the air humidity is high, the lesions quickly spread to the vines and the lesions are surrounded by severe lesions. Stems and tillers cause broken or dead stems. The leaves are affected. The first round or irregular black-brown lesions appear. The center is light brown. There are obvious black spots and concentric ring patterns on the lesions. The lesions spread rapidly in continuous rainy weather and can spread throughout the entire leaf. Black and dead. The victims suffer from the formation of water-soaked spots. The lesions in the middle turn brown and cracked in a star shape. The interior is cork-like dry rot and rots slightly after darkening. The difference between the disease and anthrax, blight and disease is that it does not harm the roots and vascular bundles. There is no pink mucous on the surface of the lesions. The center is pale and the edges have a wide brown band. There are obvious concentric rings and small circles. Dark spots and secrete amber glial.
The spore of watermelon is a fungal disease. The pathogens overwinter on contaminants and ascendants in the soil or in infected plants in greenhouses. After transplanting the host crop, the spores are released through the wind or agricultural operations and invaded through plant wounds, cracks and air holes. Seed surface can also be borne, causing seedling disease. The bacteria have strong adaptability, and the temperature requirement is not strict. It can infect at 5～35°C. The optimum temperature is 20～30°C. It will die after 10 minutes at 55°C; The relative humidity for development is 85%. . High temperature and humidity are conducive to disease occurrence and epidemic. Insufficient fertilization, weak plant growth, and poor ventilation and light transmission are prone to disease.
Agricultural control (1) rotation. Turning crops with food crops for 5 to 8 years, better crop rotations. (2) clean the pastoral. Immediately after harvest, the vines were cleared, and the surrounding leaves were burned or buried deeply to reduce the source of bacteria. (3) Select resistant varieties. (4) formula fertilization. Apply organic manure, increase phosphorus and potassium fertilizers, and do not apply nitrogen fertilizer, so that plants grow robustly and increase disease resistance. (5) Nutrient cartridge matrix colonization method. As far as possible, use the bottomless nutrient tube nursery, do not go to the tube when planting, planting depth of half a nutrition tube, can effectively alleviate the incidence of stem base. (6) Rational irrigation is done. To do sorghum, drip irrigation technology under the membrane to increase the temperature in winter and spring, reduce the incidence of disease.
Chemical control (1) Seed treatment. Before sowing, use 70% mancozeb WP 700 times or 50% thiophanate-methyl WP 500 times soaking for 1 to 2 hours to effectively control the incidence of seedlings. (2) spraying agent. At the beginning of the disease, 25% chloramphenicol cream 1500 times, or 10% difenoconazole water dispersible granules 3000 times, or 70% mancozeb WP wet spray 600 times, once every 7 days, Continuous control 2 to 3 times. The heavier fields can be sprayed with 95% mildew wettable powder 3000 times, 64% frosted MnZn wettable powder 500 times, or 70% thiophanate-methyl wettable powder 1000 times. Every 5 to 7 days, continuous control 3 to 4 times. In order to avoid affecting pollination, watermelon should be applied after 4 pm after flowering. (3) pharmacy smears. For the heavier plants, the rot tissue was scraped off and then the diseased area was smeared with 10% difenoconazole water dispersible granules 300 times or 25% prochloraz EC 150 times.
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