Introduction to the symptoms and control techniques of tomato early blight

Tomato diseases will occur in the process of tomato planting for many reasons, among which tomato early blight is one of the more serious diseases. Tomato early blight, also known as "ring disease", is common in various places, and it is one of the important diseases harmful to tomato. For a long time, tomato varieties which are resistant to virus disease but not resistant to early blight have been promoted in some areas, resulting in serious occurrence of early blight. Next, let's take a look at the symptoms and control techniques of tomato early blight.

Symptoms of tomato early blight

Tomato early blight, also known as ring rot, is one of the most important diseases of tomato. It is widely distributed, and when the disease is serious, it often causes fallen leaves and fruit to be broken branches, which has a great impact on the yield. Generally, the yield is reduced by 10%, 30%, and in some areas, it is reduced by as much as 50%. Tomato early blight can occur from seedling stage to mature stage and can damage leaves, stems and fruits. At the initial stage of the damage, the leaves produced small dark brown or black round or oval spots, which gradually expanded to a diameter of up to 1 Mel 2 cm. The lesion is dark brown at the edge, grayish brown in the center, and has concentric rims. When the humidity is high, a black mildew layer is produced on the disease spot. Finally, the diseased leaves turn yellowish brown and fall off. The disease spread upward gradually from the lower leaves of the plant. When the disease is serious, the lower leaves of the diseased plant die completely, and even cause the whole plant to fall leaves. The damage to the base often produces grayish brown, oval, slightly sunken spots on the branches, and there are also concentric wheels on them. In the later stage, the disease part of the stem is often covered with black-brown disease spots, which can cause branch breakage when the disease is serious. Most of the disease spots on the fruit occur in cracked places near the pedicel. The lesion is round or nearly round, brown or dark brown, slightly sunken, and there are concentric wheels on it. There is also a black mildew layer on the disease spot when the humidity is high. Diseased fruits often fall off early. Brown disease spots can also be produced on fruit stalks and calyx.

2. Key points of control techniques of tomato early blight.

1. In addition to disinfecting seeds and raising seedlings in non-toxic soil, scientific management and reasonable close planting should be strengthened to prevent excessive density, which is conducive to ventilation and light transmission.

2. Strictly control the temperature and humidity in the shed. Generally, the temperature in the shed is 18-20 ℃, and the relative humidity is 60-70%. Water-controlled cultivation at the initial stage of planting is suitable for watering before flowering and watering enough water in time after the formation of the second round of ear to promote the development and expansion of the fruit. Watering time should be chosen after 10:00 in the morning on a sunny day, and timely ventilation to avoid leaf condensation in the morning.

3. In the growth process of tomato planted in greenhouse, ploughing soil and cutting rod to prevent toppling should be carried out in time, old and diseased leaves should be removed and taken out of the greenhouse and buried deeply. In the middle and later stage, potassium sulfate compound fertilizer or water-soluble fertilizer was applied in time to increase disease resistance and sugar content of fruit. After fruit setting, combined with disease control, 0.2% potassium dihydrogen phosphate or potassium calcium amino acid can be sprayed on the leaves.

4. At the beginning of nursery stage, carbendazim plus agricultural streptomycin was used, and 70% mancozeb 500-fold solution spray could be selected after planting. When the disease spot is first seen, chlorothalonil or prohydantoin or complex ammonia copper and other agents are selected for prevention and treatment.