Causes of serious root-knot nematodes
1. Soil type
Generally speaking, for clay, root-knot nematodes are more likely to occur on sandy soil. This is mainly because sandy soil has better air permeability and contains organic matter, which is suitable for the parasitism and reproduction of root-knot nematodes and is conducive to the onset of root-knot nematodes.
2. Extensive use of pesticides
When farmers use a large amount of highly toxic pesticides to irrigate roots, it will not only damage the root system of crops, but also destroy the living environment of beneficial microorganisms in the soil root system, break the soil balance, and provide a good living environment for root-knot nematodes, causing root-knot nematodes to become more and more serious.
3. Applying uncomposted manure
Some farmers will directly use uncomposted manure, but when farmers apply too much uncomposted chicken manure, cow manure, sheep manure and other manure on the land, it will cause soil acidification, and acidified soil is suitable for the survival of root-knot nematodes, which will increase the harm of root-knot nematodes to crops.
4. Repeated cropping
Since root-knot nematodes are difficult to completely prevent and control, if crops are planted again in areas where the disease has occurred, root-knot nematodes are likely to occur again, because root-knot nematodes have strong vitality and can survive for 2 years in dry roots and vines and 2-5 years in idle soil.
5. Limitations of pesticides
Many farmers use pesticides to prevent and control root-knot nematodes, but the main function of chemical pesticides is to paralyze nematodes. Nematodes that have not died will enter a dormant period after being poisoned. After being in an adverse environment, when conditions are suitable for reproduction and growth, they will resume normal activities and re-infect and harm crops.
Comprehensive prevention and control methods for root-knot nematodes
1. Prevention and control from the perspective of varieties
Choose varieties with strong resistance to root-knot nematodes for planting, or use root-knot nematode-resistant rootstocks for grafting and seedling cultivation of fruits and vegetables to improve the resistance of crops to root-knot nematodes from the source.
2. Prevention and control from seedlings
Strictly control the quarantine inspection of seedlings. When sowing and raising seedlings, use soil or plots without root-knot nematodes and disinfect and sterilize them, such as using quicklime disinfection, high-temperature fumigation disinfection, etc. When planting, carefully check the roots of seedlings, remove and destroy diseased seedlings to prevent the spread of root-knot nematodes.
3. Prevention and control from the soil
Deep plowing and sun exposure
Before each sowing or planting, deep plow the soil 25-30 cm and expose it to the sun for half a month or more, using ultraviolet rays in the sun to kill root-knot nematodes.
High temperature steaming
For open fields with severe root-knot nematodes caused by long-term continuous cropping, during the high temperature rest period in summer, spread quicklime or lime nitrogen and then plow, build high ridges, irrigate sufficiently and cover with mulch to steam for half a month or more, so that the root-knot nematodes are completely killed in a high temperature, oxygen-deficient and airtight environment.
High temperature dry-wet alternating steaming
For greenhouses with severe root-knot nematodes caused by long-term continuous cropping, during the high temperature rest period in summer, the method of "spreading quicklime/lime nitrogen/strong calcium oxide on the ground → deep plowing of the soil 25-30 cm → covering the ground with film and high temperature and dry steaming for 10 days → building water dams around the edge of the ground → irrigating the ground with water and high temperature and wet steaming for 10 days" is used to carry out high temperature dry-wet alternating steaming for more than 20 days, keep the greenhouse completely closed, increase the greenhouse temperature and ground temperature, and kill the root-knot nematodes.
High temperature flooding and low temperature freezing methods
For plots with serious underground root-knot nematodes, after the previous crop is harvested, water the ground repeatedly during the summer break and around the Xiaoxue solar term in winter, and use the high temperature and humidity in summer to kill the root-knot nematodes or the freezing of the soil in winter to kill the root-knot nematodes, and keep the soil moist for half a month or more.
Improve soil
For plots with sandy soil that are prone to root-knot nematodes, spread clay on the ground every year to increase the soil viscosity and water and fertilizer retention capacity year by year, and inhibit the occurrence of root-knot nematodes.
4. Prevention and control from the planting pattern
Avoid long-term continuous planting of crops that are prone to root-knot nematodes, and implement crop rotation. For example, after planting tomatoes, eggplants, lettuce, watermelons and other fruits and vegetables on the same land for two years, it is necessary to rotate with gramineous crops such as wheat, corn, and rice, or crops such as onions, ginger, garlic, and peppers that have strong resistance to root-knot nematodes for 2-3 years (if conditions permit, it is best to implement water-dry rotation planting) to reduce the number of root-knot nematodes in the soil and reduce their harm to crops.
5. Double prevention and control from the management of repeated cropping and soil improvement
The fundamental way to prevent and control root-knot nematodes is to solve the problem of repeated cropping and improve and repair the soil. Apply high-quality organic fertilizers every year to increase soil organic matter, repair soil aggregate structure, and improve soil water and fertilizer retention capacity. At the same time, use microorganisms that can restrain and kill root-knot nematodes, such as Pseudomonas lilacinus (others such as Pseudomonas lilacinus, Bacillus thuringiensis, Verticillium chrysosporum, Trichoderma harzianum, Bacillus subtilis, etc. also have the effect of inhibiting root-knot nematodes). Although the formula of organic fertilizer + microorganisms cannot take effect immediately, long-term use can fundamentally solve the root-knot nematode damage in farmland soil, while simply irrigating and spraying can only treat the symptoms but not the root cause.
6. Prevention and control by strengthening field management
Reasonable fertilization
Increase the application of organic fertilizer and microbial fertilizer, and strictly prohibit the entry of farmyard manure, compost, poultry and livestock manure that have not been thoroughly fermented and decomposed into fields. Reasonably control the use of large chemical fertilizers, appropriately increase the use of phosphorus, potassium and calcium fertilizers, and strictly control the use of various nitrogen fertilizers.
Use functional fertilizers
Use alginic acid, humic acid, chitin, mineral potassium humate and other functional fertilizers that have the effect of promoting root growth and strengthening roots of crops 2-3 times a year or every season to enhance the growth and development of crop roots and improve their ability to resist root-knot nematode infection in the soil.
7. Prevention and control through drug use
Seize the three stages of seedling planting, peak disease period of mature plants and early stage of root-knot nematode occurrence for drug control. You can use abamectin (acaricide and insecticide) + purpurogenous spore (parasitic fungus, or purpurogenous spores, etc.) or abamectin + amino oligosaccharide crisp (a biological pesticide that can enhance crop resistance) or abamectin + fosthiazate (a pesticide that is better for preventing and controlling root-knot nematodes) and other drug formulas for root irrigation or hole pouring. Water the roots and holes once every 10-15 days to effectively prevent and control the harm of root-knot nematodes. However, it should be noted that drug control must be used in combination with farmland improvement, soil purification and field management to achieve the best control effect.
