tomato late blight is a major disease of tomato. It has occurred in all areas. The disease is very popular and destructive, often resulting in 2% ~ 3% reduction in production.

Late blight can harm tomato leaves, stems and fruits, but leaves and olives are seriously damaged.

1. Symptoms of tomato leaf injury: Generally, it starts from the lower tip or edge of the plant, and then gradually spreads to the upper leaves and fruits. At first, it was dark green water-soaked and did not reshape the lesion, and there was no obvious boundary between the lesion and the health. After expansion, it turned brown. When the air is humid, the lesion will expand rapidly, and a layer of white mold can be seen at the edge of the lesion on the back of the leaf. When the air is dry, the lesion is green-brown, then turns dark brown and gradually dries up.

2. Symptoms of tomato stem injury: the diseased spot changed from waterlogged to dark brown to dark brown, slightly sunken downwards, the diseased stem tissue softened, the plants wilted, and the stems and leaves died due to severe broken parts.

3. Symptoms of tomato fruit injury: Generally speaking, it starts from the fruit surface near the fruit stalk before being stained, and the diseased spot is an inconspicuous oil-soaked big spot, which gradually develops around, and gradually turns dark brown in the later stage, and the diseased spot is slightly sunken, the diseased fruit is hard but not soft and rotten, and the edge does not turn red. When wet, a layer of white mildew is produced on the surface of the diseased spot. Fruits can continue to suffer during storage, transportation and sales, and in severe cases, tomatoes can be destroyed in large quantities.

how to control tomato late blight and what are the specific drugs for tomato late blight?

2. Transmission route and cause of tomato late blight

1. Tomato late blight mainly overwinters in soil with diseased residues, and can also overwinter in tomatoes and potato tubers cultivated in winter. When the conditions are suitable, it is spread to tomato plants by airflow or rain, forming a central diseased plant in the field. The hyphae of the pathogen spread between host cells or cells. After 3 ~ 4 days of incubation, hyphae and sporangia grew out of the disease and were infected many times by wind and rain. Direct invasion from stomata or epidermis. The optimum temperature for mycelium development is 24℃, and the highest is 3℃.

2. Late blight occurs in all tomato plants.