Sweet potato root rot symptoms: Mainly occurred in the field period. Injured seedlings, first from the tip of the fibrous root or in the middle, local blackening and necrosis, after the expansion to the root black rot, and spread to the underground stems, the formation of brown depression longitudinal lesions, subcutaneous tissue loose. The pods on the ground are shortened and dwarfed and the leaves are yellow. The incidence of light, after the fall of pods on a large number of bud blossom; heavy disease, underground rhizome all black rot, the main stem from the bottom dry, so that the whole plant withered. Diseased potato block surface is rough, covered with dark brown spots of varying sizes, middle and late cracking, subcutaneous tissue black. Control methods: 1. Select disease resistant varieties such as Xushu 18 2. Rotation: Serious disease field rotation for more than 3 years can be used for rotation with peanuts, sesame, cotton, corn, millet and other crops. 3. Strengthen the management and cultivation of the appropriate early planting of spring potatoes, where irrigation conditions should be planted before returning seedlings to pour water once, in order to improve the resistance to disease. Summer potatoes are planted and watered in time after harvest. Deep plowing soil, increase organic fertilizer, no bacterial fertilizer applied. Preservation tubes are swabs with disposable virus sampling tubes to collect DNA tests for disposable nasal flocking sterile medical transport. swabs with disposable virus sampling tubes , to collect DNA tests for disposable nasal flocking sterile medical transport. Jiangsu iiLO Biotechnology Co., Ltd. , https://www.iilogene.com