Control methods of downy mildew of cabbage with disease spot and mildew layer connected leaves

Downy mildew of cabbage is one of the main diseases of cabbage, which not only harms cabbage, but also harms Chinese cabbage, radish, Chinese cabbage (rape) and cabbage.

Downy mildew

(1) harmful symptoms: cabbage downy mildew, mainly harmful to leaves. The lesion is polygonal, initially light green, and then becomes yellowish brown, purplish brown or dark brown. When the weather is humid, a white mildew layer grows on the back of the leaf, and sometimes on the front of the leaf, that is, sporangia and sporophore. When it is serious, the disease spot is connected into a piece, and the cabbage leaves are dry.

(2) incidence regularity: cabbage downy mildew, fungal disease. The pathogen overwinters with oospores in cabbage disease residue and soil, as well as mycelia in cabbage plants, and oospores can be attached to the surface of seeds or mixed with disease residues in seeds. In the coming year, oospore germinates and infects spring cabbage, and sporangia can be repeatedly infected by airflow.

(3) Control methods: ① selected disease-free cabbage seeds and seeds for disinfection. It is necessary to select and retain seeds from disease-free or healthy plants. Seeds can be sterilized with 50% Fumishuang wettable powder of 0.4% seed weight, or with 50% Dysenamine water 200 times solution for 15 minutes, then rinse with clean water to dry. ② is used in rotation, and cabbage is avoided from continuous cropping with cruciferous vegetables. Strengthen cultivation management, apply net fertilizer or compost farm manure. Diseased plants were found, pulled out in time, and after harvest, cabbage disease and residual plants were removed in time to reduce the source of the disease. In the early stage of ③, spray 40% ethyl phosphate aluminum wettable powder 200x-300x, or 80ppm WP 500x, or 75% chlorothalonil WP 600x, or 40% mancozeb suspension 400x. 60-80 kg of cabbage solution per mu. Spray every 7 days, 3-5 times in a row.