Occurrence and control of black rot in cabbage

Symptoms: Seedlings can not be unearthed before they are unearthed, or they die after being unearthed. In the adult stage, the leaf lesions develop from the leaf margin inward, forming a "V" shaped yellow-brown spot, and the lesions are yellowish around, and the bacteria invade from the stomata, forming an irregular yellowish brown disease on the leaves. Spot, sometimes the lesion develops along the veins into a reticular yellow vein, the ribs in the leaves are light brown, the disease is dry and rot, the leaves are twisted to one side, the leaves or plants are yellow, and some of the outer leaves are dry and fall off. When the plant is down, when the humidity is high, the diseased part produces yellow-yellow bacteria overflow or oil-soaked wet rot, which is like transparent thin paper after drying. The stem base is rotted, the plant is wilting, and the slit is visible in the slit. The seedlings developed disease, the leaves fell off, the flower buds were dark brown, and finally died, and the leaf lesions were "V" shaped. The black rot disease plant has no odor and has a mildew taste, which can be distinguished from soft rot. Chinese cabbage, which is harmed by black rot, is susceptible to infection by soft rot, which increases the degree of damage to cabbage. Morphological characteristics of pathogens: the rods are rod-shaped, and one flagella is extremely apically at the top, which can be chained and negative for Gram stain. The growth temperature range of the pathogen is 5 to 39 ° C, the optimum temperature is 25 to 30 ° C, the lethal temperature is 51 ° C for 10 minutes, and the optimum pH is 6.4. The pathogen can survive for 2 to 3 years on the diseased body. Characteristics of the disease: The bacteria overwinter with the seeds, seed plants or diseased bodies in the soil, becoming the first source of infection in the second year. The diseased seeds are sown, and the pathogens invade from the water holes at the edge of the cotyledons of the seedlings, causing the seedlings to develop. The bacteria in the soil are transmitted by rainwater, irrigation water, farming operations and insects, and the pathogens invade from the leaf edge water holes or insect bite wounds. The pathogenic bacteria of the diseased species enter the seed pods and seed coats, causing the seeds to be ill, and the disease rate of the seeds can be as high as 100%. Diseased seeds are the main route for long-distance transmission of black rot. High temperature and rain, early sowing, continuous cropping with cruciferous crops, management of extensive plots, serious pests, and serious diseases. Control methods: (1) disease-free plant seed collection and seed disinfection: seedless plant seed collection, seed disease-free. For non-healthy plant seed collection, the seeds can be soaked in 4 to 4 times with 45% dasen ammonium water for 20 minutes, washed and dried, sowed, or soaked in warm water at 50 °C for 20 minutes, cooled with cold water, or 0.3% by weight of seeds. 50% Fumei double wettable powder dressing. Be careful not to soak seeds with streptomycin to avoid phytotoxicity. (2) Rotation: Two to three years of rotation with non-cruciferous crops. (3) Strengthen field management: timely sowing, timely watering in the seedling stage, reasonable seedlings, timely removal of field diseased plants and carrying out deep burial in the field, and disinfecting the diseased points. (4) Pharmacy prevention and treatment: timely spraying in the early stage of the disease, the prevention and treatment can be sprayed with agricultural streptomycin or neomycin oxytetracycline 4000 times solution or 47% ruinong WP 600-800 times liquid plus harvest first 1000 times liquid, or Vegetable Fengning B1 300 grams per acre plus 60 liters of water spray or 250 liters of water.

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