Key Technical Points for Integrated Pest and Disease Control in Chinese Yam
I. Agricultural Control 1. Selecting disease-resistant varieties is an effective method for controlling Chinese yam pests and diseases. When cultivating disease-resistant varieties, rational layout is necessary, rotating varieties every 2 to 3 years, and attention should be paid to variety purification and rejuvenation. 2. Crop rotation can reduce or avoid damage from Chinese yam stem rot and root-knot nematodes. Rotate at least once every 3 years with crops that are not infected, such as corn (2343, -3.00, -0.13%), wheat, radish, and watermelon; in old areas where Chinese yam is cultivated year-round, rotate once every year; where conditions permit, paddy-upland rotation can be implemented for better control results.
I. Agricultural Control
1. Selecting disease-resistant varieties is an effective method for controlling Chinese yam pests and diseases. When cultivating disease-resistant varieties, rational layout is necessary, rotating varieties every 2 to 3 years, and attention should be paid to variety purification and rejuvenation.
2. Crop rotation can reduce or avoid damage from Chinese yam stem rot and root-knot nematodes. Rotate at least once every 3 years with crops that are not infected, such as corn (2343, -3.00, -0.13%), wheat, radish, and watermelon; in old areas where Chinese yam is cultivated year-round, rotate once every year; where conditions permit, paddy-upland rotation can be implemented for better control results.
3. Land preparation can directly eliminate pathogenic bacteria that overwinter in the soil. Choose high, dry terrain with low humidity and fertile, loose sandy loam soil, and carry out land preparation in autumn. This can turn diseased residue left on the surface into the soil, accelerating the decomposition and rotting of diseased residue, and through winter freezing and spring sun exposure, some pathogens lose their viability.
4. Fertilization and irrigation. Chinese yam is a fertilizer-loving crop, so thoroughly decomposed organic fertilizer must be applied during land preparation. Generally, increasing phosphorus and potassium fertilizer helps the formation of mechanical tissues in Chinese yam and enhances resistance to pathogenic bacteria. Applying too much nitrogen fertilizer easily causes excessive vegetative growth, making stem and leaf tissues tender and susceptible to Chinese yam anthracnose. The principle of watering is "do not water unless dry"; when watering, use clean water sources, and be sure to water thoroughly. There must be no standing water in the field, and drainage should be timely during the rainy season to avoid root rot.
5. Field sanitation. Field weeds are best removed manually. Promptly remove the leaves and stems of diseased Chinese yam, which can reduce re-infection by pathogens. At harvest time, diseased residue, weeds, and rotting stems left on the ground should be centrally burned or taken outside the field for deep burial to reduce overwintering pathogens.
II. Chemical Control
1. Chinese yam anthracnose damages stems and leaves, causing stem blight and leaf drop. Control method: Soak seed tubers in 1:1:150 Bordeaux mixture for 10 minutes. At full emergence, spray the first application with 50% carbendazim 600 times dilution, and spray a second time 10 days later. If disease is found in July to August, use 65% zineb wettable powder 500 times dilution, 50% thiram wettable powder 800 to 1000 times dilution, or 50% thiophanate-methyl 700 to 800 times dilution, and spray 2 to 4 times depending on disease severity, alternating sprays. The interval between each application should be 8 to 10 days, and the spray solution should be reapplied after rain.
2. Root-lesion nematode disease causes plant stunting, and in severe cases the whole plant turns yellow and dies; when tubers are damaged, small galls of varying sizes appear, affecting yield and quality. Control method: Treat the soil with chemicals before sowing. Use 5% meclofenphos granules 5 kg per mu mixed with 100 kg of moist fine soil, open furrows and evenly broadcast on both sides of the seed tubers, or evenly broadcast in combination with land preparation, incorporating into the soil at 25 to 30 cm.
3. Sawflies bite and eat Chinese yam leaves, causing severe leaf loss, affecting photosynthesis and leading to reduced tuber yield. Spray stems and leaves with 2% deltamethrin 3000 times dilution or 90% trichlorfon crystal 1000 times dilution.