Vegetables are not growing well. What's the matter with a lot of pimples? How to prevent it?

This is a root-knot nematode disease caused by the harm of root-knot nematodes in vegetables. The disease occurs in the roots of vegetables. After the plant is damaged, it is characterized by slow growth, short plant and pale leaves. With the aggravation of the disease, the leaves gradually turn yellow and wither, which can seriously lead to the death of the whole plant. When the roots are pulled apart, it can be seen that there are many spherical or nearly spherical nodules (nodules) of different sizes on the lateral roots and fibrous roots, some of which are beaded and some are chicken feet, and there are many fibrous roots on the surface. Nodules are white at first, soft in texture, light brown in later stage, with cracks on the surface, which often cause rot under the joint infection of other microorganisms. Cut open the root knot and you can see many tiny white nematodes under the magnifying glass.

Root-knot nematodes can harm almost all kinds of vegetables, among which solanaceous fruits, beans, melons, carrots and celery are seriously damaged, while onions, garlic and leeks are slightly damaged.

In recent years, the harm of root-knot nematode disease in protected vegetables has become more and more serious. With the extension of continuous cropping time, the incidence of some crops susceptible to root-knot nematodes, such as cucumber and tomato, in the old shed is as high as 40% ~ 100%, which has a great impact on the growth and yield of vegetables, from 20% ~ 30% to 50% ~ 70% or even no production.

The prevention and control of vegetable root-knot nematode disease should focus on controlling the source of the disease and reducing the initial infection in greenhouse, and adopt comprehensive prevention and control measures with agricultural and biological control as the main part, supplemented by chemical control.

(1) soil disinfection

In summer, the high-temperature greenhouse and soil were disinfected during the high-temperature stubble changing period. The specific method is described in the previous part of this book.

(2) Planting disease-resistant varieties

Tomato, eggplant and other varieties resistant to root-knot nematodes have been cultivated abroad. Tomato varieties introduced from China, such as Ruili, Ruiguang and Dutch Gc779, have moderate resistance.

(3) selecting disease-free soil to raise seedlings.

Appropriate application of quicklime before planting can make the soil weakly alkaline, which also has good control effect.

(4) Rotation

The serious illness shed can be rotated with Gramineae crops or onions, garlic and leeks for 2-3 years, or it is better to implement paddy-upland rotation.

(5) Chemical control

Before planting, 2 kg 10% thiamethoxam granules are mixed with 20 kg of soil, evenly spread on the border surface, evenly mixed with the surface soil (15 ~ 20 cm), and then seedlings are planted. The efficacy lasts about 45 days, and the control effect is about 95%. For untreated vegetable fields before planting, or vegetable fields with mild diseases, 2% avermectin EC 1000 times solution can also be used for root irrigation, and the control effect is about 85%.