Prevention and control of white spot on leaf surface like roast Chinese cabbage

White spot mainly harms the leaves of Chinese cabbage. At the onset of the disease, there are many gray-white near-round disease spots on the leaves, with two irregular wheel patterns in the middle and yellowish halos on the periphery. The outer edge of the disease spot on the back of leaves is dark green, but sometimes it is not obvious. Finally, the spot is white, translucent and fire-like. Sometimes the plaque will break or fall off. In the late stage of the disease, they were connected into irregular mass dead spots. When the air is moist, the back of the disease spot is gray and mildew.

White spot of Chinese cabbage

Prevention and control methods:

1. Select disease-resistant varieties of Chinese cabbage.

2. Practical treatment of seeds: mix Chinese cabbage seeds with 75% chlorothalonil or 50% thiram wettable powder, the dosage is 0.3% of seed weight, and mix Chinese cabbage seeds with 50% prohydantoin wettable powder, the dosage is 0.2% of seed weight.

3. Strengthen cultivation management: 2-3 years rotation of vegetables in serious disease areas and non-cruciferous vegetables. Leveling the land, applying more base fertilizer, sowing at the right time, preventing stagnant water in the field, removing residual plants and fallen leaves in the field after harvest, deep ploughing and burying in the soil can reduce bacteria, cultivate strong plants and reduce the incidence of disease.

4. Chemical control: when there is sporadic disease in the field, any of the following pesticides can be sprayed: 50% carbendazim wettable powder 500 times, 40% carbendazim suspension 800 times, 75% methyl topiramate wettable powder 800 times, 70% mancozeb wettable powder 500 times. When Chinese cabbage mildew and white spot occur at the same time, 40% ethyl phosphorus aluminum wettable powder can be mixed in carbendazim solution. Spray once every 10 days for 3 times in a row.