Control techniques of stem nematode disease of sweet potato

Sweet potato stem nematode disease is a destructive disease in sweet potato production, which is harmful and spreads quickly. It can infect and harm in seedling stage, field stage and storage period, but it mainly infects potato pieces. The skin of the injured sweet potato is brown, green, tortoise cracks, light pieces, some potato pieces have the same appearance, but the inner bran heart. The disease not only affects the quality of sweet potato, but also seriously affects the yield of sweet potato.

Sweet potato stem nematode disease is caused by a parasitic stem nematode. The pathogenic nematode is slender wormlike, slightly pointed at both ends and 0.9-1.45mm in length. It can overwinter as adults, larvae and eggs in potato blocks, as well as adults and larvae in soil and manure. The worm is not resistant to high temperature and can die after immersed in 50 ℃ warm water for 10 minutes. The insect likes moisture and is tolerant to low temperature. It stops its activity at-15 ℃, but does not die. It is dry-tolerant and can survive for one year in extremely dry environment. Therefore, it is difficult to eradicate the worm.

The following comprehensive measures can be taken to control sweet potato stem nematode disease:

1. Select disease-resistant varieties: that is, when introducing varieties, excellent varieties with disease resistance and virus-free should be selected, which are suitable for local planting. For example, the excellent varieties suitable for planting in the Central Plains and resistant to stem nematode disease are Jishu 10, Yushu 13, Sushu 8, Beijing 553 and so on.

2. Cultivate disease-free and strong seedlings: sprinkle 60 grams of carbofuran granules per square meter of seedling bed, and then cover the soil; soak the seeds in 52-53 ℃ warm water for 10 minutes, which can kill the nematodes at the depth of 7 mm under the skin of seed potatoes; after cutting the second crop of seedlings, sprinkle aldicarb again (watering after application) or sprinkle it with methyl isomalidophos. As there are many stem nematodes at the base of the seedlings, high shearing seedlings can be taken, that is, after the seedlings are collected, the roots of the seedlings are cut off 3-5 cm, and then soak the seedlings with 50% phoxim or 50% methyl isomaliphate 150-200 times solution for 30 minutes.

3. Establish disease-free seed field, that is, use disease-free land as seed field, and strictly select seed potato and seedlings. Summer potatoes should be collected from the nursery or cut from the spring potato field and planted in disease-free land for next year.

4. Chemical control: 2000-2500 times solution of methyl isofenphos or phoxim was used in the serious disease area to irrigate 0.50kg per hole when planting seedlings, and aldicarb granule or Stem Ling granule, 1-1.5kg per mu, was applied at the hole when planting, and then watered. In mild disease area, 150-200 times solution of methyl isofenphos or phoxim was used to dip the base of seedlings for 30 minutes before planting, and the control effect was very good.

5. eliminate insect sources: when raising seedlings, planting and harvesting every year, remove diseased potato lumps, diseased seedlings and diseased plant remains, dry them in the sun, burn them or cook them as feed. Diseased potato peel, washing water, feed residue, diseased soil and diseased seedling bed soil should not be used as retting fertilizer raw materials, but should be fermented at a high temperature of more than 50 ℃ when used as fertilizer.

6. Crop rotation: rotation should be carried out in seriously diseased land, sweet potato should be rotated with wheat, corn, millet, cotton and tobacco, and sweet potato should not be planted every 3 years, which can basically control the occurrence and harm of stem nematode disease.

7. adjust the time of seed and harvest: in the seriously sick area, the early planting of spring potato was postponed to the middle of May, and the harvest was advanced to the end of September or the beginning of October, so as to avoid the peak period of nematode damage, and timely sliced and dried as brewing raw material or cooked as feed.

8. Strengthen quarantine: that is, to implement a strict quarantine system. Cross-regional transfer of diseased potatoes and seedlings is strictly prohibited to prevent the expansion of epidemic areas.