Tomato early blight, also known as tomato ring spot, is one of the most important diseases of tomato. The diseased leaves produce dark brown or black circular spots at the initial stage, and then expand into dark brown circular, oval or irregular large spots, with dark concentric ring patterns in the center of the diseased spots. Surrounded by a yellow halo. Lesions on the stems and fruits are nearly round, dark brown, with black fluffy mold and concentric ring patterns. Generally, the disease starts from the lower leaves of the plant. In severe cases, the lower leaves of the plant are completely dead, exposing the fruit and easily causing sunburn.
The pathogen of this disease is a kind of fungus. The black mold on the lesions is the conidia of the fungus.
Tomato Early Blight
Incidence law: The pathogen of tomato early blight mostly overwinters with mycelium or conidia in the soil or attached to the seeds along with the diseased residue. When the conditions are favorable in the following year, it will be spread by wind and rain, and invade from stomata, lenticels, wounds or epidermis, causing disease, and there are many re-infections in the field. As a result, the onset was severe during the peak period. When the temperature is 20-25°C, the relative humidity is above 80% or the weather is cloudy and rainy, the disease is easy to spread. Heavy cropping land, low-lying land, barren land, overwatering or poorly ventilated land are more severely affected.
Prevention methods:
① Plant resistant and disease-tolerant varieties, choose early-maturing varieties, and harvest early, which can reduce the occurrence of diseases.
② Crop rotation: 2 to 3 years of crop rotation with non-Solanaceae crops.
③ Seed disinfection: Soak seeds in warm soup or medicament.
④ Strengthen cultivation and management: apply fully decomposed organic base fertilizer, reasonably close planting, pay attention to ventilation and light transmission in protected areas, reduce humidity, and drain water in time after rain. Remove diseased leaves and fruits in time in the early stage, and take them out of the field for centralized destruction.
⑤ Pharmaceutical control: In the early stage of the disease, spray with 3% Nongkang 120 water agent 150 times or 2% Wuyimycin 150-200 times, spray once every 5-7 days, and spray 2-3 times continuously. Scrape off the lesions on the stalks first, and then apply 1:10 of 3% Nongkang 120 liquid medicine, the control effect is the best. Expert Tip: When tomato early blight occurs, ventilation and light transmission should be strengthened, the humidity in the greenhouse should be reduced, and timely prevention and control should be carried out to avoid spreading.
