How to prevent and control early blight of tomato? Latest technical method tutorial
Tomato early blight occurs in Northeast China, North China, East China, Southwest China and other regions of our country. Its most important feature is that no matter whether the lesions occur on fruit, leaves or main stems, they all have obvious concentric rings, so it is also called ring spot disease. Fruit lesions are often near the fruit stalk, stem lesions are often at branching points, and leaf lesions occur on the leaf mesophyll. Now let us take a look at the prevention and control techniques for tomato early blight!
Symptoms of tomato early blight damage
Tomato early blight mainly damages leaves, and can also damage seedlings, stems and fruits. When seedlings are infected, dark brown lesions appear at the stem base, slightly sunken and with concentric rings. When leaves are damaged at the adult plant stage, the disease mostly develops from the lower leaves upward. At first, water-soaked dark green lesions appear, and after expansion they become round or irregular ring-spotted lesions, with edges mostly having a light green or yellow halo, and the center showing concentric rings. When humid, black mold grows on the lesions, and in severe cases the leaves fall off. When stems are infected, the lesions are mostly at branching points and the base of leaf stalks, appearing as brown to dark brown irregular round or oval lesions, sunken, with concentric rings, sometimes cracked, and in severe cases causing branch breakage. When green fruits are infected, it mostly starts near the calyx, initially as oval or irregular brown or black spots, sunken, and later the fruit cracks, the diseased part is relatively hard, and black mold is densely produced. When leaf stalks and fruit stalks are infected, the lesions are grayish brown, long oval, and slightly sunken.
Occurrence pattern of tomato early blight
Tomato early blight is caused by infection by Alternaria solani. The pathogen overwinters in soil or on seeds, spreads by wind and rain, and invades through stomata, lenticels, wounds or the epidermis, causing disease. The pathogen can cause multiple secondary infections in the field, and the disease is severe during the peak fruiting period. When the temperature is 20-25°C, relative humidity is above 80%, or the weather is rainy, the disease is prone to epidemic. Continuous cropping land, low-lying land, barren land, and plots with excessive watering or poor ventilation have more severe disease.
Chemical control of tomato early blight
1. At the early stage of disease, promptly remove diseased leaves, diseased fruits and severely diseased branches, and begin spraying fungicides. To prevent resistance and improve control efficacy, rotation, alternation or compound use is recommended, spraying once every 7 days for 2-3 consecutive sprays.
2. When the disease is relatively severe, remove the central diseased plants, diseased leaves, etc., and promptly adopt a control method combining Chinese and Western approaches.
Agricultural control of tomato early blight
1. Cultivate strong seedlings: adjust the temperature and humidity of the seedbed well, and transplant seedlings when the seedlings have grown to two leaves and one heart, and be careful to prevent excessive seedling growth. This can prevent disease during the seedling stage.
2. Crop rotation: tomatoes should be implemented in a three-year rotation system with non-Solanaceae crops.
3. Strengthen management: implement high-ridge cultivation, fertilize reasonably, and after transplanting and seedling recovery, promptly close the rows to promote new root development. In greenhouses, control temperature and humidity well, and strengthen ventilation and light transmission management. During the fruiting period, regularly remove lower diseased leaves, bury them deeply or burn them, to reduce the chance of disease transmission.