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, leading to their accumulation and multiplication in the soil. Crops such as cucumbers and tomatoes, which are often grown continuously, have been particularly affected. These nematodes cause significant yield losses or even total crop failure, and the incidence of the disease continues to increase each year.
I. Symptoms of Damage
Root-knot nematode diseases primarily affect cucumbers, zucchini, tomatoes, and eggplants, with cucumbers and tomatoes being the most vulnerable. The nematodes attack the roots of plants, especially 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, bean-like nodules, while in cucumbers, the galls can vary in size and shape. When cut open, the galls contain small, white, needle-like particles—these are the adult female nematodes.
The above-ground parts of infected plants show restricted growth, though symptoms may not be immediately obvious. Plants grow slowly, leaves turn yellow, and the overall growth is stunted, resulting in small fruits and poor yields. As the disease progresses, the plants eventually die.
II. Prevention and Control Measures
(a) Thorough removal of infected roots and targeted treatment: After harvesting vegetables in greenhouses or fields, it's crucial to clear the soil promptly to reduce the disease source and lower infection rates.
(b) Crop rotation: Rotating crops is a simple yet effective method to reduce nematode populations in the soil. For example, rotating with onions or garlic can help suppress nematode infestations.
(c) High-temperature extermination: During the summer heat, applying 500 kg of ammonium bicarbonate per acre, followed by deep plowing, watering, and covering with plastic mulch, can effectively kill nematodes. If the greenhouse film is not removed, this process should last 20 days; otherwise, 40 days are needed.
(d) Disinfection of seedbeds: When growing seedlings, use new, uninfested soil or spray the seedbed with 3 liters of 1.8% avermectin diluted 2000 times per square meter. Mix well and then use nutrient-rich soil to raise healthy seedlings.
(e) Soil treatment before planting: Mix 1.8% avermectin at a rate of 1.8 liters per mu with 500 ml of Lebensin, water it in, and plant immediately. Alternatively, apply 0.5% avermectin granules at 3–4 kg per mu before planting.
These measures can significantly reduce the impact of root-knot nematodes and improve crop health and productivity.
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