Viral disease is the main disease of spring soybeans. The annual production is reduced by about 15% in the year of incidence, and the yield is reduced by more than 50% in the re-issue year. Timely pesticide control is necessary.
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1. Symptoms: After the onset of spring soybeans, the upper leaves appear pale yellow-green mottled, the mesophyll is bulging along the veins, and then the mottled shrinkage is getting heavier, the leaves are deformed, the mesophyll is protruding, the leaf margin is rolled, and the plant grows. Obviously dwarfed, the number of pods decreased, the pods were small, and the pods were flat and curved. After the onset of spring soybeans mature, the bean granules are significantly reduced, and can cause light brown markings on the beans.
2. There are three kinds of pathogens of spring soybean virus disease: 1 soybean mosaic virus (SMV), SMV infects soybeans and causes soybean mosaic symptoms. 2 Cucumber mosaic virus (CMV), CMV caused soybean atrophy symptoms and bean grain striate. 3苜蓿 Mosaic virus (AMV), AMV causes the mosaic symptoms of soybean leaves, which is characterized by distinct yellow markings. The three viruses that cause soy virus disease often infect soybeans at the same time. The symptoms in the field are often not single symptoms, but mixed symptoms.
3. Influencing factors 1) Variety of disease resistance Different soybean varieties have significant differences in disease resistance to viral diseases. Liaoxian No.1 and Japanese short-legged early resistance are strong. The 75 varieties introduced in Taiwan in the past few years have been growing in quality due to their high quality and high yield. However, Taiwan's 75 varieties have poor disease resistance and are prone to viral diseases. The degree of onset is heavier.
2) Climate factors The weather is dry and drier. On the one hand, it has adverse effects on soybean growth, which reduces disease resistance. On the other hand, it is conducive to the growth and activity of aphids, and aphids are the main medium for transmitting soybean virus diseases. Therefore, the weather is dry and rainy, especially in April and May, with drought and less rain, and the incidence of soybean virus disease is heavy.
3) According to the China Pesticide Network , the cultivation management factors strengthen the management of soybean fertilizer and water, so as to increase the application of potassium fertilizer and phosphate fertilizer in a timely manner, timely irrigation and watering in dry weather, timely clearing the weeds in the field and surrounding, and cultivating robust soybean plants can improve the resistance to viral diseases. Sex. Appropriate early spring soybean sowing period can reduce the incidence of viral diseases.
4. Prevention and control 1) Select disease-resistant varieties, establish disease-free seed fields, and use non-brown spots and full bean seeds as seeds.
2) Strengthen fertilizer and water management, cultivate robust plants, and enhance disease resistance.
3) Control mites early, and control the mites from the seedling stage to prevent and reduce virus infection.
4) The use of chemical agents to control spring soybean virus disease should start from the seedling stage, so as to improve the control effect. It can be combined with the prevention and treatment of aphids in seedling stage. The agent can be selected from 20% virus A500 times solution or 1.5% phytotoxic milk 1000 times solution, or 5% fungicide toxic solution 400 times solution, continuous use 2~3 times, once every 10 days. 
Occurrence and prevention of soybean virus disease