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 ha halo, which has 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; when it is heavy, on the leaf 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 Chinese cabbage seeds and directly infect the seedlings. Therefore, before the sowing of Chinese cabbage, seed dressing is carried out with 50% imazonose wettable powder having a seed weight of 0.2% to 0.3%.

2 Control field humidity: In the easy onset period, the field is humid and 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: After the black spot disease pathogen invades the leaves of Chinese cabbage, the disease spots can be formed after 3 to 5 days, and the black mold can be produced on the lesions, and then the Chinese cabbage is invaded. Therefore, when the lesion appears on the lower leaves of Chinese cabbage, it can be sprayed, 50% isoform urea wettable powder 1500 times solution, or 75% chlorothalonil wettable powder 600 times liquid, every 7 to 10 Spray once a day, even spray 3 to 5 times, 50 kg per spray of liquid per 667 square meters.

4 Foliar fertilizer: If the plant grows weak, in addition to strengthening the management of water and fertilizer, 0.2% potassium dihydrogen phosphate or 1% red (white) sugar can be added to the sprayed liquid to supplement the leaf surface.

5 Note: 1 plots that are susceptible to disease. 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.

Reprinted from Dr. State Pesticide Biocide Station http://

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