How to prevent and control spring soybean virus disease? Detailed explanation of occurrence patterns and control methods
Viral disease is a major disease of spring soybean, causing about 15% yield loss in normal outbreak years and over 50% yield loss in severe outbreak years.
1 Symptoms After spring soybean is infected, the upper leaves first show light yellow-green mottling, and the mesophyll bulges in a blister-like manner along the veins; then the mottling and wrinkling become increasingly severe, the leaves become deformed, the mesophyll protrudes, the leaf margins curl downward, plant growth is clearly stunted, the number of pods decreases, the pods are small and slender, and the pods show deformed symptoms such as flattening and bending. After infected spring soybean matures, the seeds are clearly smaller, and light brown streaks can appear on the seeds.
2 Pathogens There are 3 pathogens of spring soybean viral disease: ① Soybean mosaic virus (SMV); after SMV infects soybean, it causes soybean mosaic symptoms. ② Cucumber mosaic virus (CMV); CMV causes soybean stunting symptoms and ring-patterned seeds. ③ Alfalfa mosaic virus (AMV); AMV causes mosaic symptoms on soybean leaves, characterized by bright yellow markings. The 3 viruses causing soybean viral disease often infect soybean at the same time, and the symptoms shown in the field are often not a single symptom but mixed symptoms.
3 Influencing factors
3.1 Disease resistance of varieties Different soybean varieties differ clearly in resistance to viral disease. Liaoxian No. 1, Japanese Short-foot Early and others have relatively strong disease resistance. In previous years, the introduced Taiwan 75 variety continued to expand in planting area because of its good quality and high yield, but Taiwan 75 has poor disease resistance, is prone to viral disease, and the disease severity is relatively heavy.
3.2 Climatic factors Dry weather with little rain, on the one hand, adversely affects soybean growth and reduces disease resistance; on the other hand, it favors the growth and activity of aphids, and aphids are the main vector for spreading soybean viral disease. Therefore, dry weather with little rain, especially drought and little rain in April to May, leads to severe soybean viral disease.
3.3 Cultivation and management factors Strengthening fertilizer and water management for soybean, rationally increasing potassium fertilizer and phosphate fertilizer, timely irrigation and watering in dry weather, timely clearing weeds in the field and around it, and cultivating robust soybean plants can improve resistance to viral disease. Appropriately advancing the sowing date of spring soybean can reduce the occurrence of viral disease.
4 Control
4.1 Select disease-resistant varieties, establish disease-free seed production fields, and select plump seeds without brown spots as seed.
4.2 Strengthen fertilizer and water management, cultivate robust plants, and enhance disease resistance.
4.3 Control aphids early, starting from the seedling stage, to prevent and reduce virus infection.
4.4 Chemical control of spring soybean viral disease should start from the seedling stage so as to improve control efficacy. It can be applied together with aphid control at the seedling stage. The agents can be 20% Virus A at 500 times dilution or 1.5% Zhibingling emulsifiable concentrate at 1000 times dilution, or 5% Junduqing at 400 times dilution, used continuously 2 to 3 times, once every 10 days.