Control of celery late blight in greenhouse

Celery late blight, also known as spot blight and leaf spot, is a common disease in celery. The late blight of celery planted in greenhouse is more serious than that of celery in open field, which has a great effect on the yield and quality of celery. Occurrence characteristics: celery late blight is a fungal disease, which can survive the winter on seeds and remnants. Sowing diseased seeds causes disease immediately after emergence, produces conidia, and spreads in the seedling bed. The source of overwintering bacteria on the diseased remains, under suitable conditions, produce conidia to spread by wind and rain, infect celery, and then produce conidia for repeated infection. The pathogen grows well under cold and wet conditions, and the optimum temperature for the disease is 18Mel 25 ℃, and the humidity is more than 95%. Celery in the greenhouse generally has a serious disease. In case of continuous rainy weather, frequent temperature fluctuations, or foggy dew, plant growth is weak, it is conducive to the rapid expansion and spread of the disease. The disease can continue to develop during the Tibetan period, and the loss is often more severe than in the field. Prevention and control methods. In order to prevent and control celery late blight, we should first strengthen fitness cultivation. In addition to selecting and sowing disease-free seeds and doing a good job of seed disinfection, we should also apply fully mature soil fertilizer in fertilizer and water management, prevent partial application of chemical nitrogen fertilizer, and implement rill irrigation. Do not irrigate too much water and water temperature, maintain loose ventilation of vegetables in vegetable fields, and properly spray plant growth hormone and foliar fertilizer to increase plant disease resistance. At the same time, we should do well the ventilation and moisture drainage of the greenhouse and the management of heat preservation at night, reduce the temperature difference between day and night, reduce plant dew, control bacterial infection, eliminate the residual leaves of diseased plants and reduce the source of bacteria in the field. When the disease is first seen in the field, it is necessary to pay close attention to spraying control. At present, the better agents for the prevention and control of celery late blight are: 75% chlorothalonil wettable powder 600 times, or 64% antiseptic alum M8 500 times wettability, or 40% polysulfide suspension 500 times, generally 50 million 75 kilograms per mu, one of the above chemicals is optional, sprayed every 7 times 10 times, 2 times 3 times.