Occurrence and control of soybean blight

Soybean seedling blight is commonly known as "dead tree","damping-off" and "black root disease". In serious disease years, the death rate of plants in light disease fields is 5%~10%, and the death rate of plants in serious disease fields is more than 30%. Some fields even die completely, resulting in no yield. 1. The symptoms of disease in the field were that the disease occurred only at seedling stage, reddish brown slightly depressed spots appeared at the base of taproots and stems near the ground, the cortex dehisced and ulcerated, and the hyphae of the pathogen were colorless at first and gradually turned brown later. Disease serious, short appearance, slow growth, stem by the ground russet, cortex cracking, was ulcerated. 2. The disease condition is continuous cropping, rotation is light. Because of the accumulation of bacteria in the soil for years increased the number of bacteria. Poor seed quality and disease severity. The pathogen of bacterial wilt can be transmitted by seeds, and it is related to the decrease of germination potential and disease resistance of seeds. The earlier the sowing, the longer the seedling grows in the field. Compost from diseased plants can transmit disease severity without decomposition. The disease was serious in the fields with many underground pests, poor soil quality, lack of fertilizer and poor soybean growth. 3. Disease resistant varieties were selected as control methods. Seed dressing. Seed dressing with 0.3% of seed amount of 40% clofos-methyl EC or 50% thiram WP. Seed crop rotation, 3-year rotation with gramineous crops. Choose dry land with good drainage to grow soybean. Low-lying land shall be planted in ridges or high ridges and deep grooves, with reasonable dense planting to prevent excessive surface humidity and timely drainage after rain. Watering depends on soil moisture and temperature. 4. At the beginning of the disease, the following agents were sprayed: 40% aluminum triethylphosphonate WP 200 times;70% ethyl phosphate WP 200 times; Manganese zinc wettable powder 500 times solution;58% metalaxyl? Manganese zinc wettable powder 500 times solution;69% Anke manganese zinc wettable powder 1000 times solution once every 10 days, continuous control 2~3 times, and spray evenly and fully.