Brown spot of Chinese cabbage

The symptoms were yellow-brown dots at first, and then expanded into round to oval, or irregular black-brown spots with a diameter of 4mm and obvious edges. When the disease is serious, the disease spots are connected to each other, and the diseased leaves wither and die. The disease occurs easily in rainy and humid weather or out-of-season cultivation. Chemical control methods: (1) 35% metalaxyl seed mixture with 0.3% seed weight. (2) spraying 58% metalaxyl at the initial stage of the disease? Manganese zinc wettable powder 500 times liquid, 50% nail cream copper wettable powder 600 times 700 times liquid, or 64% poison alum wettable powder 500 times liquid, 40% aluminum triethylphosphonate (frost epidemic) wettable powder 250 ~ 300 times liquid, 72.2% Pulicol water agent 800 times liquid, 50% imipramine wettable powder (Polydo) 355g / mu, 70% Bingsen zinc wettable powder (Antaisheng) 150g / mu 25% Amisida suspension 25g / mu, 64% 100? Manganese and zinc wettable powder (Fumidol, Weir, Caifukang) 100g / mu, 50% isobaric urea wettable powder (prohydantoin) 50g / mu, 10% difenoconazole water dispersible granule (Shigao) 35g / mu, 25% methyl sulfur? Nitrile wettable powder (SK) 100g / mu, more than 25%? Manganese and zinc wettable powder 100g / mu, 5% hexazolol suspension (Anfu) 60g / mu, 40% flusilazole EC (Fuxing) 10g / mu, once every 7 days, continuous control for 2 times. Agricultural control (1) selection of disease-free seeds. (2) the disease is limited to infecting rosette vegetables. After 2-3 years of rotation, the disease control effect is good. (3) pay attention to the discharge of stains in the field and ventilation of sparse plants.