Integrated Control of Diseases, Pests and Weeds in Pollution-Free Sweet Potato Cultivation

(1) Carefully select seed tubers. Choose tuber pieces free of disease, insects and injuries as seed tubers. 

(2) Chemical treatment of seed tubers (omitted). 

(3) Storage cellar management. Store the seed tubers in a sterile cellar; preferably use a new cellar. If an old cellar is used, first scrape off the cellar walls, then fumigate with 15 g of sulfur per sq m. Within three days after the tubers are stored, use a flue to let fire heat into the cellar, raise the temperature to 37-39°C, maintain it for 48 hours, open the door, and let the cellar temperature drop and remain at 11-13°C. 

(4) Seedbed management. (1) Use fresh soil from a new bed and manure free of disease and insects for raising seedlings. (2) Control humidity well. Before treating the seed tubers, keep the seedbed temperature above 25°C. After treating the seed tubers, further remove diseased, injured and frost-damaged tubers while arranging them on the bed. In the first week after the seed tubers are placed on the bed, keep the bed temperature at 30-34°C, then keep it at about 25°C. (3) Remove diseased seedlings. During seedling raising, inspect the seedbed every 5-7 days, and when virus-diseased and other diseased plants are found, pull them out together with the seed tubers. (4) High cutting of seedlings. Cut the seedlings 3-5 cm above the ground. For spring sweet potatoes, cut once; for summer sweet potatoes, cut twice, that is, cut the seedlings high from the seedbed, plant them in an open-field nursery, and then use the seedlings from the second high cutting in the open-field nursery to plant in the main field. Never pull seedlings (to prevent black spot disease). Use branches high-cut from the stems as sweet potato slips (to prevent stem nematode disease). 

(5) Treatment of sweet potato slips. (1) Before planting, strictly remove diseased slips and cut off diseased parts. (2) Chemical treatment. According to the type of disease, choose any one of the following methods: ① Soak the base of the stems 6-10 cm deep for 10 min in 1000-2000 times dilution of 50% carbendazim wettable powder or 500-700 times dilution of 50% thiophanate-methyl wettable powder, then insert cuttings, to control smut. ② Soak high-cut sweet potato slips in warm water at 45°C for 5 min, then immediately place them in warm water at 50°C for 4 min, take them out and rinse with cold water, to prevent stem nematode disease. ③ Planting soil. For every 667 sq m, evenly mix 0.25-0.35 kg of 50% phoxim with 20-25 kg of fine soil and dry it. When planting slips, first apply the poisoned soil into the planting holes, and after the liquid has seeped down, plant the slips, to control stem nematode disease.