Control techniques of Tomato early Blight

Tomato early blight has occurred in Northeast, North China, East China, Southwest and other regions of China. Its main feature is that no matter the disease spot on the fruit, leaf or main stem, there are obvious wheel lines, so it is also called wheel grain disease. The fruit disease spot is often near the fruit stalk, the stem disease spot is often in the bifurcation, and the leaf disease spot occurs in the mesophyll. Let's take a look at the prevention and control techniques of tomato early blight.

Symptoms of tomato early blight

Tomato early blight mainly harms leaves as well as seedlings, stems and fruits. The seedlings are infected with a dark brown spot at the base of the stem with a slightly sunken wheel pattern. When the leaves were killed in the adult stage, most of them developed upward from the lower leaves of the plant, showing a water-immersed dark green disease spot at the beginning, a round or irregular wheel spot after expansion, a light green or yellow halo on the edge and a concentric wheel pattern in the middle. Black mildew layer grows on the disease spot when it is wet, and the leaf falls off when it is serious. The stem is infected, the disease spot is mostly in the branches and the base of the petiole, brown to dark brown irregular round or oval spot, sunken, with concentric wheel lines, sometimes cracked, sometimes causing broken branches. Green fruit infection, mostly began near the calyx, the initial oval or irregular brown or black spots, depression, late fruit cracking, the disease is hard, dense black mildew layer. Petiole, fruit stalk infected, disease spot grayish brown, long oval, slightly sunken.

Incidence regularity of tomato early blight

Tomato early blight is caused by Alternaria solanum infection. The pathogen overwinters on soil or seeds, spreads through wind and rain, invades from stomata, lenticels, wounds or epidermis, and causes the disease. The pathogen can be re-infected many times in the field, resulting in serious disease in the peak period. When the temperature is 20-25 ℃, the relative humidity is more than 80% or the weather is cloudy and rainy, the disease is easy to spread. The incidence of continuous cropping land, low-lying land, barren land, overwatering or poorly ventilated land is more serious.

Chemical Control of Tomato early Blight

1. In the early stage of the disease, diseased leaves, diseased fruits and seriously diseased branches were removed in time, and germicidal pesticides were sprayed in time. In order to prevent the development of drug resistance and improve the control effect, alternate or compound use was advocated, spraying once every 7 days and 2 times in a row.

2. When the disease is serious, remove the central diseased plants and diseased leaves, and adopt the prevention and treatment method of integrated traditional Chinese and western medicine in time.

Agricultural Control of Tomato early Blight

1. Cultivate strong seedlings: adjust the temperature and humidity of the seedling bed, divide the seedlings when the seedlings grow to two leaves, and beware of overgrowing seedlings. It can prevent disease at seedling stage.

2. Rotation: tomato should be rotated with non-Solanaceae crops for three years.

3. Strengthen management: high ridge cultivation should be carried out, rational fertilization should be carried out, and ridges should be closed in time after planting slow seedlings to promote the occurrence of new roots. The temperature and humidity in the greenhouse should be well controlled, and the management of ventilation and light transmission should be strengthened. During the fruit period, the lower diseased leaves should be removed regularly, buried or burned, so as to reduce the chance of spreading the disease.