How to Prevent and Control Sweet Potato Stem Nematode Disease? Detailed Technical Methods

Sweet potato stem nematode disease is caused by infection by a parasitic stem nematode. The pathogenic nematode is slender and worm-like, with both ends slightly pointed, and a body length of 0.9-1.45 mm. It can overwinter in tubers as adults, larvae, and eggs, and can also overwinter in soil and manure as adults and larvae. This nematode is not tolerant of high temperatures; immersion in 50°C warm water for 10 minutes kills 98%. It prefers moisture and tolerates low temperatures. At -15°C it stops activity but does not die; it also tolerates dryness and can survive for 1 year under extremely dry environmental conditions. Therefore, completely eradicating this nematode is relatively difficult. 

To prevent and control sweet potato stem nematode disease, the following integrated measures can be taken: 

1. Select disease-resistant varieties: When introducing varieties, choose excellent disease-resistant, virus-free varieties suitable for local planting. For example, excellent varieties suitable for planting in the Central Plains region and resistant to stem nematode disease include Jishu No. 10, Yushu No. 13, Sushu No. 8, Beijing 553, etc. 

2. Cultivate disease-free strong seedlings: Spread 60 grams of 3% carbofuran microgranules per square meter of seedbed, then cover with soil; before the seed potatoes are placed in the hotbed, soak the seeds in 52-53°C warm water for 10 minutes, which can kill nematodes 7 mm deep under the seed potato skin; after cutting the second batch of seedlings, spread aldicarb again (water after application) or pour with methyl isofenphos liquid. Because there are many stem nematodes at the base of the seedlings, high cutting of seedlings can be adopted, that is, after harvesting the seedlings, cut off 3-5 cm from the root part of the seedlings, then soak the seedlings in 150-200 times dilution of 50% phoxim or 50% methyl isofenphos for 30 minutes. 

3. Establish disease-free seed reservation fields: Use disease-free plots as seed reservation fields, and strictly select seed potatoes and seedlings. For summer sweet potatoes, collect seedlings from the nursery or cut vine tips from spring sweet potato fields and plant them in disease-free land to reserve as seed for the next year. 

4. Chemical control: In severely diseased areas, use 2000-2500 times dilution of methyl isofenphos or phoxim, and pour 0.50 kg per hole when transplanting seedlings; aldicarb granules or stem nematode spirit granules can also be used, at 1-1.50 kg per mu, applied in holes at planting time, then watered. In lightly diseased areas, use 150-200 times dilution of methyl isofenphos or phoxim, and before planting, dip the base of the seedlings for 30 minutes; the control effect is very good. 

5. Eliminate sources of the pest: Every year during seedling raising, planting, and harvest, remove diseased tubers, diseased seedlings, and diseased plant residues, and concentrate them for sun-drying and burning or boiling as feed. Diseased potato skins, water used for washing potatoes, feed residues, soil from diseased fields, and soil from diseased seedbeds should not be used as composting materials. If used as fertilizer, they must undergo high-temperature fermentation above 50°C. 

6. Crop rotation: Severely diseased plots should be rotated. Sweet potatoes should be rotated with wheat, corn, millet, cotton, and tobacco. If sweet potatoes are not planted for more than 3 years, the occurrence and damage of stem nematode disease can be basically controlled. 

7. Adjust planting and harvesting times: In severely diseased land, change early planting of spring sweet potatoes to planting in mid-May, and harvest early by the end of September or early October, so as to avoid the peak period of nematode damage, and promptly slice and sun-dry them as brewing raw material or boil them as feed. 

8. Strengthen quarantine: Implement a strict quarantine system. It is strictly forbidden to transport diseased potatoes and diseased seedlings across regions, in order to prevent the expansion of the epidemic area.