In recent years, with the adjustment of agricultural planting structures, the area under protected cultivation for vegetables has expanded rapidly. This change has created an ideal environment for the proliferation of root-knot nematodes, allowing them to accumulate and multiply in the soil. Continuous cropping of crops such as cucumbers and tomatoes has worsened the problem, leading to significant yield losses or even total crop failure. The incidence of this disease has been increasing year by year, posing a serious threat to vegetable production.
**I. Symptoms of Damage**
Root-knot nematode infections primarily affect cucumbers, zucchini, tomatoes, and eggplants, with cucumbers and tomatoes being the most severely impacted. These nematodes attack the roots of plants, particularly the fibrous and lateral roots. Infected roots develop bead-like, spherical, or conical swellings known as root galls. In tomatoes, the roots often appear as clusters of small, grain-like nodules, while cucumber roots may form various-sized nodules on the lateral roots. When cut open, these galls contain small, transparent white particles—female nematodes.
The above-ground parts of infected plants are stunted, showing slow growth, yellowing leaves, and overall poor development. Fruits are small and unmarketable. As the infection progresses, the plants gradually wilt and die, causing significant economic losses to farmers.
**II. Prevention and Control Measures**
(a) **Complete removal of infected plant residues**: After harvesting vegetables in greenhouses or fields, it is essential to thoroughly remove all plant debris from the soil to reduce the nematode population and minimize future infestations.
(b) **Crop rotation**: Implementing a rational crop rotation system is one of the most effective ways to control nematode populations. For example, rotating with onions or garlic can help suppress nematode numbers in the soil.
(c) **Thermal elimination**: During the summer months, when temperatures are high, apply 500 kg of ammonium bicarbonate per acre, mix it into the soil, water thoroughly, cover with plastic mulch, and keep it sealed for 40 days (or 20 days if the greenhouse film remains intact). This method effectively kills nematodes.
(d) **Disinfection of seedbeds**: When raising seedlings, use new, disease-free soil or treat the seedbed with 3 liters of 1.8% avermectin diluted 2000 times per square meter. Mix well and then transplant healthy seedlings.
(e) **Soil treatment before planting**: Apply a mixture of 1.8% avermectin (1.8 liters per mu) and 500 ml of Lebensin in water. Spray the surface immediately and then till and plant. Alternatively, use 0.5% avermectin granules at a rate of 3–4 kg per mu, applied directly into the planting holes.
By implementing these integrated management strategies, farmers can significantly reduce the impact of root-knot nematodes and improve the sustainability of their vegetable production systems.
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