Occurrence and control of Sclerotinia sclerotiorum in soybean

Sclerotinia sclerotiorum is a common disease on soybean crops, which mainly causes stem rot, pale lesions, hollow stems and black sclerotia, which is easy to break. In the past two years, soybean Sclerotinia sclerotiorum has a tendency to increase year by year. Causes and characteristics: 1. Sclerotinia sclerotiorum is a fungus with a large number of sclerotia in the field, which forms cylindrical or mouse dung-shaped sclerotia on the soybean stem, its shape is irregular, the size is 1mm × 4mm × 3mm, and the sclerotia germinates under rainy, wet and light conditions. the pathogenic fungi overwintered by sclerotia scattered in the soil and mixed among seeds, and seeds can also carry bacteria. two。 Environmental factors in the flowering stage of soybean, high soil surface temperature, high air humidity and heavy rainfall are conducive to the occurrence of the disease. 3. If the seed sclerotia is used as the seed harvested in the previous year, the sclerotia residue in the seed may be increased and the occurrence of soybean sclerotia disease will be aggravated year by year. 4. The occurrence of Sclerotinia sclerotiorum was serious in the plots with high planting density. The reason is that excessive close planting will cause poor ventilation and excessive humidity, which is conducive to the disease; soybean sclerotinia disease occurs seriously in the plots adjacent to sunflowers and rape; in addition, soybean sclerotinia disease occurs seriously in continuous cropping plots. Prevention and control countermeasures: 1. Reasonable rotation of soybean Sclerotinia sclerotiorum only spreads harm to soybean, sunflower and rape, but does not infect Gramineae crops. Therefore, it is necessary to reform the farming system, implement rotation for more than three years, avoid being adjacent to sunflowers and rape fields, and control the spread of Sclerotinia sclerotiorum. two。 Before sowing selected seeds, the sclerotia mixed in soybean seeds should be screened, and disease-resistant seeds without sclerotia should be selected for sowing. 3. Strengthen cultivation management, reasonable close planting, desilting and waterlogging control, leveling the land, opening ditches and drainage, preventing stagnant water and water transmission, shoveling in time before ridge sealing of soybean, and eliminating germinated sclerotia and ascomycetes. The seriously affected plots of soybeans should be turned deep after harvest, and the diseased remains and sclerotia should be turned into the ground. 4. Chemical control in the flowering stage of soybean, soybean sclerotia just began to germinate and unearthed to the peak stage of the formation of ascomycetes, 1500 times of 50% Sukeling wettable powder was sprayed on the surface of ridge soil, or 1000 times of 50% Nongliling wettable powder was sprayed with 30 kg. The plot sprayed with the above chemicals can control soybean Sclerotinia sclerotiorum by more than 85%.