Tobacco mosaic disease comprehensive prevention and control of pesticides

Tobacco mosaic disease is one of the three major diseases that affect tobacco crops. It can occur during the early seedling stage or in the field, significantly impacting the yield of tobacco plants. Although the disease has less effect on yield after topping, it greatly affects the quality of the final product. The disease is caused by a variety of viruses, with common mosaic and cucumber mosaic being the most prevalent types. Effective control requires a dual approach: chemical pesticide application and comprehensive prevention strategies. First, let's look at the symptoms: 1. **Common Mosaic Disease**: Infected plants show yellowing along the veins of young leaves, followed by the formation of irregular yellow-green mottles. In severe cases, leaves become thick, wrinkled, and twisted, with curled edges and visible damage such as nicks or ribbon-like deformities. Early infection can cause stunted growth, shortened internodes, and poor leaf development. 2. **Cucumber Mosaic Disease**: Initially, the veins of the leaves become transparent, and later the leaves narrow and twist. The surface loses its luster, and some leaves curl upward, forming yellow-green or dark green vesicles. In some cases, brown necrosis appears along the lateral veins, resembling lightning patterns. Affected plants are often dwarfed, with stunted roots and "flower spot" lesions on the leaves. Second, understanding the disease's spread is crucial: 1. **Common Mosaic Disease**: The virus can survive for long periods in infected plant material, soil, seeds, and other hosts like tomatoes, canola, and weeds. It spreads through mechanical contact, entering through small wounds caused by friction. Human activity, wind, and insects all contribute to transmission. The disease is more common in areas near villages, tobacco houses, roadsides, and previous tobacco fields. Poor soil conditions, such as compact or poorly drained land, also increase the risk of infection. Temperatures between 18-30°C are ideal for the disease to develop. 2. **Cucumber Mosaic Disease**: Unlike the common mosaic virus, cucumber mosaic cannot survive in dry tobacco under natural conditions. It overwinters in vegetables and perennial weeds. In spring, it spreads through aphids and wind. Areas with high weed density, proximity to vegetable fields (such as cucumbers and tomatoes), and hot, dry weather tend to have higher incidence rates. Excessive nitrogen use and poor soil structure can also worsen the problem. Third, here are key prevention and control measures: 1. **Select resistant varieties**: Planting disease-resistant varieties such as Kirk 176, K394, G346, K326, and NC series can significantly reduce the risk of infection. 2. **Optimize seedbeds and crop rotation**: Choose well-drained, fertile fields for seedbeds, away from vegetable plots and tobacco processing areas. Implementing rice-water rotation helps reduce pathogen buildup. 3. **Soil disinfection**: Use lime or methyl bromide in severely affected areas. Proper soil preparation can eliminate pathogens, pests, and weeds. 4. **Improve cultivation practices**: Early planting, proper irrigation, and balanced fertilization promote strong, healthy growth and improve plant resistance. 5. **Maintain cleanliness**: Remove diseased leaves, weeds, and debris regularly. Avoid using contaminated farmyard manure or tobacco waste as fertilizer. After harvest, burn all plant residues to prevent re-infection. 6. **Control aphids**: Apply insecticides such as 40% omethoate, 20% speed killing, or 50% anti-Poly at recommended dilutions. Silver mulching can also help reduce aphid populations by creating an unfavorable environment for them. 7. **Effective spraying**: According to the China Pesticide Network, it is important to spray during critical stages such as seedling emergence, transplanting, and post-transplanting. Solutions like 20% Viral B500, 1.5% phytopathogenic, 1% virus agonist, or 83-1 reinforced agent can be used for treatment. By combining these strategies, farmers can effectively manage tobacco mosaic disease and ensure better yields and quality.

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