After sowing of cotton, if it is cloudy and the temperature is low, it will seriously affect the normal growth and development of cotton, resulting in serious damage to cotton seedlings and death of cotton seedlings. The mortality rate of cottonseedlings is about 1.20%, and it is more than 4% in heavier years, and 12.40% in heavier lands, with or without emergence. The disease that damages the cotton seedling stage is mainly cotton blight, and often mixed with cotton seedlings anthrax and red rot. 1 If the main symptoms of cotton are infested by bacteria before sowing, it will lead to bad seeding, bad buds, and can not be normally excavated. After being unearthed, the cotton seedlings are also vulnerable to pathogenic bacteria within half a month. The symptoms of the cotton seedlings are yellowish-brown spots on the roots and stems of the cotton seedlings, followed by long brownish depressions, curled into bee-waisted shapes, and the cotyledons wilting. The seedlings fall flat and die. When the roots were damaged, the phloem rotted dark brown fibers. When the diseased seedlings are pulled out of the soil, the diseased part often has hyphae with small soil particles. 2 Pathways Pathogens in the soil can attach to diseased or uncomplicated composts for wintering. Cotton seed and seedlings will be directly infested. The pathogenic mycelium produced on the damaged cotton seedlings can continue to harm the adjacent healthy seedlings and expand and infect again. Therefore, the onset of the disease often causes severe ridges and lack of seedlings in the cotton field. Bacteria concurrently parasitize and saprophytic, can survive in the soil for a long time. 3 Onset conditions The occurrence of the disease is closely related to climate, soil and other conditions, low temperature, high humidity is conducive to the occurrence of diseases, so after the planting of cotton, in case of low planting of rain, or a long period of low temperature, the soil temperature is large, The disease is serious. If the temperature rises or the soil temperature decreases, the disease will stop developing. 4 Prevention and cure method 1 Rotation: In the previous year, the heavier plots could be rotated with cereal crops. Such as wheat, corn, etc., cereal crops have a certain degree of resistance. 2 Autumn tillage and winter irrigation Fine soil preparation: The deep fall of the cotton field can turn the sick and broken leaves into the soil to reduce the source of the disease in the coming year; winter irrigation can reduce the soil temperature and reduce the ground temperature due to the pre-planting irrigation, so as to grow cotton seedlings. Create favorable conditions. 3 Select good seeds for proper seed treatment sowing: High-quality cotton seeds are the basis for cultivating strong seedlings. Seeds should be selected and sun-dried before sowing, so that proper sowing can be performed to improve the quality of sowing. The use of coated seeds or seed dressing can provide very good control. 4 Strengthen the seedling management for the cotton fields that are currently diseased: After the cotton seedlings are unearthed, and time seedlings, fixed seedlings, and cultivating loose soil. When thinning and fixing seedlings, they adhere to the principle of “removing weak and strong seedlings†to reduce pathogens and infringe upon cotton seedlings and transmission routes. At the same time, the cultivator loose soil can increase the ground temperature by 1～3°C, promote the development of the root system of cotton seedlings, make it robust and grow, and increase the disease resistance.
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