With the increasing area and years of cultivation of fruits and vegetables in greenhouses and cold sheds, the incidence of root-knot nematodes is gradually increasing. Root-knot nematodes are common in all greenhouses, especially in some old sheds that have been planted for many years. Root-knot nematodes not only affect the normal growth of crops, but also aggravate the occurrence of other diseases. Therefore, it has become a headache for growers.
What are the symptoms of crops being damaged by root-knot nematodes?
Root-knot nematodes mainly occur in the roots, and the affected parts are lateral roots and fibrous roots. Most of the above-ground symptoms are not very obvious. When the roots are damaged, tumors of different sizes are formed on the roots. Tumors are also called "root knots". The root knots are white in the early stage, yellow-brown or black-brown in the later stage, and rot in the most serious cases.
When crops are attacked by root-knot nematodes, the early symptoms of the aboveground part are not very obvious. As the root damage becomes more serious, the aboveground part gradually shows yellowing leaves, lack of water, lack of fertilizer, wilting, slow growth, poor fruiting, weak plants, etc., and the most serious ones lead to crop death.
What are the ways of transmission of root-knot nematodes?
Root-knot nematodes can overwinter in the soil and can be spread with the help of rainwater and irrigation water. They invade from the young roots of crops until they develop into adults and become parasitic nematodes. In the process of feeding, root-knot nematodes can secrete irritants to stimulate the enlargement of crop root cells, thereby forming root knots or nodules.
The initial sources of infection of root-knot nematodes are diseased soil, diseased seedlings, and irrigation water. The mobile transmission is mainly wind, flowing water, diseased species, farm tools, and human farming operations.
Causes of root-knot nematode disease
Root-knot nematode disease has a great relationship with soil and terrain. Root-knot nematode development and activity are not conducive to moist clay soil and soil compaction. However, in high and dry terrain, loose structure, low salt sandy soil, it is suitable for root-knot nematode activity, which is also the reason for the severe disease.
Root-knot nematode disease is also closely related to the planting system. If a field is cropped continuously for many years, the greater the probability of disease, the longer the continuous cropping time, the more serious the crop damage.
Environmental temperature and humidity are important causes of root-knot nematode disease. The suitable temperature for root-knot nematode is 25℃-30℃. It is less active when it is below 5℃ or above 40℃. It can be lethal if it lasts for 10 minutes at 55℃. The soil moisture conditions suitable for vegetable growth are also suitable for root-knot nematodes, with a humidity of 40%-70%.
How to prevent and control root-knot nematode disease?
Reasonable crop rotation can reduce soil nematodes and reduce the occurrence of diseases. The effect is more significant if 2-3 years of crop rotation is implemented. It can be rotated with gramineous crops, because gramineous crops will not be affected by root-knot nematode disease.
Farm management of disease-free soil seedling raising and deep plowing of soil can effectively prevent the occurrence and development of root-knot nematode disease; thoroughly treat diseased and damaged plants, burn or bury them in a centralized manner, and apply fertilizer and water rationally, which can delay the symptoms of diseased plants or reduce losses. Deep plowing before sowing can turn the nematodes distributed in the topsoil layer deep into the soil. Increasing the application of organic fertilizer can increase the strength and toughness of the root system and improve the resistance and tolerance of plants.
Use purpurogenous purpurogenous nematodes to completely kill root-knot nematodes through biological pathways. Purpurogenous purpurogenous microorganisms are endoparasitic fungi and are important natural enemies of some plant parasitic nematodes. It can significantly reduce the harm of plant nematode diseases such as root-knot nematodes, cyst nematodes, and stem nematodes in various crops. The purpurogenous fungus reproduces quickly and has strong vitality. It can secrete and synthesize a variety of organic acids, enzymes, and physiologically active substances to stimulate crop growth, so that the seedlings are full, green, and strong.
Root-knot nematode disease can be prevented and controlled comprehensively, with the policy of "prevention first, prevention and control combined", and the principle of "agricultural prevention as the main, chemical prevention as the auxiliary".
