Tomato planting techniques: why does autumn tomato late blight occur?

Why does autumn tomato late blight occur? Please introduce the causes and control methods of autumn tomato late blight, which is a disease of low temperature and high humidity. The air relative humidity is more than 80%. The optimum humidity for the development of the pathogen is 20-22 ℃ in the daytime and more than 10 ℃ at night. It is easy to develop in the case of low temperature, overcast and rain, high humidity, foggy in the morning and night. It is easy to cause diseases in continuous cropping land, partial application of nitrogen fertilizer or excessive density, lack of light and poor ventilation. There are also possible causes of the disease: first, crop rotation is difficult: with the expansion of planting area, rotation is difficult, continuous cropping makes bacteria in the soil accumulate year by year, and the harm is aggravated. Second, improper treatment of diseased plants in the field: some growers accumulate plant remains in the field without deep burial or burning, and residual leaf disease can be seen everywhere in the fruit field. Third, climatic factors: generally speaking, there are more overcast and rainy weather in autumn, the temperature is low and the field humidity is high, which creates favorable conditions for the spread of late blight. Fourth, the consciousness of disease prevention is not strong: some growers do not adhere to the prevention principle of "giving priority to prevention, prevention is more important than cure". After the onset of the disease, the frequency of medication is not enough, and there is no supplementary spray in the rain after spraying, which all lead to poor prevention and control effect. Prevention and control methods of autumn tomato late blight: pay attention to ventilation, adjust temperature and control humidity, avoid leaf dew or form water film, avoid overcast and rainy days after watering, and properly control watering after onset. It was found that 72% frost urea manganese zinc wettable powder, 68% fine nail cream manganese zinc water dispersible granule, 52.5% azolidone urea cyanide water dispersible granule, 25% pyrimethrin suspension, oligomale Pythium wettable powder (not used with chemical pesticides, should be sprayed in the morning or evening, and should not be sprayed in the sun or before rain). Smoke control at room temperature should be used as far as possible. Click to get more tomato planting techniques click to get more vegetable planting techniques