The celery spot blotch is a common disease in the production of protected celery. At present, winter is approaching, and the environmental conditions of low temperature and high humidity are extremely conducive to the occurrence and epidemic of the disease. It is timely to prevent and control the occurrence and spread of diseases and increase production and income.
First, the symptoms
The leaf blight of celery mainly damages the leaves, followed by the petiole and stem. The old leaves first develop from outside to inside. At the beginning of the lesion, the spot was light brown oil-immersed and the edges were obvious. Afterwards, it developed into irregular spots. The color changed from pale yellow to grayish white, and the edges were dark reddish-brown, and many small black particles were gathered. The lesions often had a yellow circle outside. Halo ring. Petiole, stem lesions brown, slightly concave depression, scattered black dots in the middle, when dry leaves dry rotten.
Second, the incidence of the law
The celery spot blight is a kind of fungal disease. The low temperature and high humidity are beneficial to the occurrence of the disease. The most suitable temperature for the disease is 20°C～25°C, and the humidity is above 95%, and the incidence of celery in the protective field is heavier. Even the cloudy days, frequent temperature fluctuations, or hot daytime, dew condensation at night, weak plant vigor, more irrigation, and lack of timely ventilation and dehumidification can often lead to the rapid spread of the disease.
Third, control methods
1. Apply disease-free seed or seed disinfection. The lethal temperature of the celery leaf spot blight is 48°C to 49°C. Therefore, it can be soaked in hot water at this temperature for 30 minutes before field sowing, and stirring is continued during soaking.
2. Balanced fertilization. The base fertilizer should be applied with fully decomposed organic fertilizer. Apply phosphorus and potassium fertilizer in the topdressing, control the amount of nitrogen fertilizer, and spray some foliar fertilizer and trace fertilizer as much as possible to enhance the resistance of the plant.
3. Cooling and humidity. During the day, the temperature is controlled between 15°C and 20°C. When the temperature exceeds 20°C, the air should be released in a timely manner. At night, the temperature should be controlled between 10°C and 15°C to reduce the temperature difference between day and night, reduce condensation, and prevent flooding.
4. Chemical control. Prevention of the disease should be sprayed on the celery seedlings when the height of 3 cm, spray every 7 to 10 days, and even spray 2 or 3 times. In the onset of greenhouses, 45% of chlorothalonil aerosol can be used, 200-250 grams of smoke per mu, or 5% of chlorothalonil powder, 1000 grams of powder per acre, easy to apply, and reduce the humidity in the greenhouse. Dusting agent can also be used 70% mancozeb WP, 58% MnZn WP, 64% WP, 75% WP, 50% carbendazim wettability Powder and so on.
5. Remove diseased plants in time. For the sheds that have already been attacked, the diseased plant residues in the shed must be promptly removed to reduce the spread and spread of the bacterium source.
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