Recent investigations have found that the occurrence of early blight of tomato after the fall is heavier, and farmers should step up prevention and treatment. Tomato early blight, also known as "ringworm disease," occurs widely throughout the country and is one of the most important diseases that harm tomato. This pathogenic host has a wide range of pathogens, which can also harm eggplants, peppers and other solanaceous vegetables in addition to harming tomatoes.

First, the symptoms

The disease mainly damages tomato leaves and can also damage seedlings, stems and fruits. Seedlings were infected, resulting in dark brown spots on the base of the stem, with a slight depression in the ring pattern. In the adult stage, the leaves are attacked, mostly from the lower leaves of the plants. The water-immersed dark green lesions appear at the beginning, and the expanded or irregularly shaped lenticular veins are spotted. The edges are light green or yellow halo rings. Concentric ring pattern, black mold layer grows on the lesions in the wet, serious leaves fall off; stem disease, lesions in the branches and petiole base, brown to dark brown irregular round or oval lesions , sag, with concentric ring lines, sometimes cracked, severely caused by broken branches. The diseased fruits are mostly found near the calyces. They were initially oval or irregularly shaped brown or black spots, sag, and later fruit cracking. The diseased part was hard and dense black mold layer. Petiole, pedicel infected, lesions gray-brown, long oval, slightly concave.

Second, the incidence of the law

The disease is a fungal disease. It spreads through the wind and rain and invades the host directly from the stomata, lenticels and epidermis. After 4-6 days, a large number of conidia are produced and expanded to re-infect. High temperature and humidity are conducive to the occurrence and prevalence of the disease. The field temperature of 15°C and relative humidity of 80% began to develop. The temperature ranged from 20°C to 25°C, with foggy or even cloudy days, and the disease progressed rapidly.

Third, control methods

1. Agricultural control. Selection of disease-resistant varieties, such as Chinese vegetable No. 4, Su Kang No. 5 and so on. Pay attention to selecting seeds from disease-free plots and disease-free plants. Before sowing, it can be treated with warm water of 52°C (natural cooling) for 30 minutes, then soaked in cold water to germinate. Since pathogens can have a survival period of more than one year in the soil, it is important to pay attention to crop rotation, and it is generally more than 3-4 years of rotation with non-solanum plants. Nursery bed should be enough base fertilizer, application of phosphorus, potash fertilizer, planting deep trenches and high ridges, adjust the planting density (4000 per acre is appropriate). Small water to be poured, to prevent flooding irrigation, pay attention to ventilation and humidity, to avoid excessive humidity.

2. Chemical control. Can choose to use 64% anti-virus WP 500 times, 50% acetaminophen WP 1000 times or 70% MnZn wettable powder 500 times spray, spray every 7 days, even spray 3 - 4 times, 50-60 kg per mu. If the combination of early blight and late blight occurs, 58% metalaxyl MnZn WP can be used to spray. If there is a lesion in the stem, apply 50% peiocin WP 200 times to the affected area.

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