Chinese cabbage black spot disease is a fungal disease. In the northern part of the country, it is easy to develop from September to October. The nearly round lesions with a diameter of 2 to 10 mm appear on the leaves of the damaged Chinese cabbage. The lesions are brown or light brown. There is a yellow halo with a distinct concentric pattern. When the humidity is high, there is a black mold on the back of the leaf (as a pathogen), and it can harm other Chinese cabbage by airflow. The lesions can be connected to each other, causing the leaves of the diseased plants to turn yellow from the outside to the inside, often causing large economic losses. The main control measures are as follows.
1. Seed treatment: The pathogen of black spot disease can be attached to the seeds of Chinese cabbage and directly infect the seedlings. Therefore, before the Chinese cabbage is planted, it can be seeded with 50% Fumei double wettable powder with a seed weight of 0.4%, or 50% of the hydantoin wettable powder with a seed weight of 0.2% to 0.3%.
2, control the humidity in the field: in the easy onset period, the field humidity is high, the incidence is heavy. 1 suitable for seedlings. According to the characteristics of Chinese cabbage, soil fertility and other factors, appropriate plant spacing should be used in the appropriate period (Taiyuan area can not be later than in early September) to improve the field ventilation conditions. 2 Reasonable watering. In the easy onset period, it is necessary to "see the sky, see the ground, and see the growth of Chinese cabbage". Watering should be done according to the amount of water in the right time. Water in the field should be discharged early.
3, early spraying: black spot disease pathogens invaded the leaves of Chinese cabbage, after 3 to 5 days can form lesions, and the disease spots can produce black mold, and then invade Chinese cabbage. Therefore, when the lesion appears on the lower leaves of Chinese cabbage, it can be sprayed, and 75% chlorothalonil wettable powder 600 times solution, or 50% chlorhexidine WP 1500 times solution, or 50% Fumei double can be used. Wettable powder 500 times solution, or 64% anti-virus 矾 wettable powder 500 times solution, spray once every 7 to 10 days, even spray 3 to 5 times, 50 kg per spray solution per 667 square meters.
4, foliar fertilizer: If the plant grows weak, in addition to strengthening water and fertilizer management, you can also add 0.2% potassium dihydrogen phosphate or 1% red (white) sugar to the sprayed liquid to supplement the foliage.
5, note: 1 easy to disease plot. With the cruciferous vegetable flail and the neighboring land, the land that has not been seeded and planted, the land that has been planted too early, the field where the plant density is large, the land with insufficient base fertilizer and top dressing, the land where the plant grows weak, the big water The land that is flooded is easy to develop. 2 vulnerable vegetables. In addition to Chinese cabbage, radish, broccoli, rape (cabbage or green vegetables), broccoli (cauliflower), etc., are susceptible to infection by this disease, and control measures can refer to Chinese cabbage.
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