Cabbage black rot is an important disease that jeopardizes cabbage. It can occur from the seedling stage to the ball-forming stage. After harming the leaves and flower balls, the flower ball loses its commercial value, causing a reduction in production and causing serious losses to the vegetable farmers. Therefore, it is necessary to prevent and cure the black rot of cabbage in time, so as to cure the disease, cure the disease, and cure it.
Symptoms identify cabbage black rot that primarily harms leaves, leaves or bulbs. In the seedling stage, the cotyledons are water-soaked and quickly die or spread to the true leaves. In the early stage of the disease, the first step is from the leaf margin, and the "V"-shaped yellow-brown spots appear at the apex of the leaf marginal veins, gradually spreading the entire leaf margin to form a yellow-brown band. In the case of 5-10 true leaves at the time of onset, the lowermost leaves begin to wilting and yellowing, and then the whole plant gradually withers; if it occurs in the rosette period, the black leaves appear on the cabbage sphere, the ball is soft and not solid, and the commodity value is completely lost. . Once the disease occurs, the infection area is large and the incidence rate is fast, which will cause serious reduction in production.
Regular pathogens overwinter on the seed or with the diseased body in the soil, from the leaf edge of the seedling cotyledon or true leaf, invaded by water holes or wounds, and quickly enter the vascular bundle to cause the disease at the base of the leaf. The germs can be spread through farm tools and rain. High temperature and high humidity, continuous cropping, poor soil drainage, large amount of nitrogen fertilizer application, small application of organic fertilizer and potassium fertilizer and trace elements such as zinc, manganese and molybdenum, and imbalance of soil microbial environment are beneficial to the survival and reproduction of pathogens.
Control methods (1) Agricultural control. Soak seeds with warm water at 50 ° C for 20-30 minutes, or soak for 15 minutes with 0.1% copper sulfate solution. The severely affected plots and cruciferous vegetables are subject to a 2-3 year rotation. Improve soil supply and drainage conditions, and increase application of organic fertilizer, phosphorus and potassium fertilizers and micro-fertilizers. (2) Chemical control. The seedbed is disinfected with 50% dexamethasone 800-1000 times liquid spray wet soil or 50% carbendazim 800 times liquid watered seedbed. In the early stage of the disease, 14% solution of lycopene copper water 600 times, or 77% copper hydroxide wet powder 500 times solution, or 72% agricultural streptomycin soluble powder 5000 times solution, 7-10 days 1 time, even spray 2 -3 times.
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