How to prevent and control early blight of tomatoes?

What should we do if tomatoes have early blight? How can we better prevent and treat it? Here are some specific methods:

Prevention and treatment of tomato early blight:

Tomato early blight is also called ring rot. Autumn delayed tomatoes are most susceptible to this disease because they are grown in greenhouses with high humidity, insufficient light, and low photosynthetic products. Therefore, autumn delayed tomato early blight should be discovered and treated early to avoid unnecessary economic losses to vegetable farmers.

The disease is a fungal disease. The lesions are oval and have ring patterns. The leaves are the main target. It is spread by wind and rain, and directly invades the host through the stomata, lenticels and epidermis. After 4 to 6 days, a large number of conidia are produced to expand and re-infect. High temperature and high humidity are conducive to the occurrence and spread of the disease. The disease begins when the field temperature is 15℃ and the relative humidity is above 80%. The temperature is 20℃~25℃, foggy or cloudy, and the disease develops rapidly. The prevention and control methods are as follows:

For agricultural prevention and control, disease-resistant varieties such as Zhongshu No. 4, Sukang No. 5, Qiguo, etc. are selected. For seriously diseased fields, 3-4 years of crop rotation with non-eggplant vegetables are implemented. Sufficient base fertilizer is applied, phosphorus and potassium fertilizers are added, deep furrows and high ridges are planted, and the planting density is adjusted to 4,000 plants per mu. Water carefully with small amounts of water to prevent flooding, pay attention to ventilation and moisture removal, and avoid excessive humidity.

Chemical control Chemical control can be done with 500 times of 64% chlorpyrifos WP, 1000 times of 50% chlorpyrifos WP, or 500 times of 70% mancozeb WP. Spray once every 7 days for 3-4 times in a row, and use 50-60 kg of liquid per mu. If early blight and late blight occur together, 500 times of 58% metalaxyl·mancozeb WP can be used. If there are lesions on the stem, 200 times of 50% chlorpyrifos WP can be applied, which has a good effect.