How to treat the blight of broccoli?

Symptoms:

The pathogen mainly infects the root neck of the seedlings, causing the root neck to become black or constricted, and the leaves are wilted and dry after a few days of plant infection. Generally, the spread of the pathogen stops after colonization. Transmission route and disease condition: The pathogenic fungi belong to the subphylum hemiomycete, which mainly overwinter in soil or diseased residues with mycelium or sclerotium. The mycelium in the soil lives saprophytically and is not dormant, mainly through contact infection, that is, when the roots, stems and leaves of the plant contact the soil with bacteria, they will be infected by the bacteria in the soil, and under the condition of water film, the leaves in contact with the disease are also susceptible to disease. In addition, seeds, furniture and bacteria-laden compost can spread the disease. Prevention and control methods: ① Strengthen the management of seedbeds: choose a place with high terrain and good drainage to build seedbeds, choose fresh and disease-free soil as bed soil, use rotten organic fertilizer, pay attention to the sowing density should not be too large, the seed soil should not be too thick, should be watered a small number of times, and pay attention to ventilation after watering. (2) Mix 40% pentachloronitrobenzene powder with 50% Fumi double wettable powder in equal amounts, use 9-10 grams per square meter of seedbed, mix in 3-4 kilograms of fine soil, sprinkle 1/3 of the medicated soil on the permeable seedbed surface before seeding, and cover the remaining soil on the seeds after seeding, so that the seeds are sandwiched in the middle of the medicated soil. ③ At the early stage of the disease, 600 times diluent of 75% chlorothalonil wettable powder, 500 times diluent of 36% methylthiobacillam suspension or 450 times diluent of 15% oxazoline water can be sprayed once every 7-10 days, depending on the condition. Spray 2-3 times consecutively.