Tomato late blight is one of the main diseases of tomato. In addition to damaging tomatoes, it can also damage potatoes, eggplants, etc. The disease mainly affects leaves and fruit, but can also affect stems. Irregular dark green water-soaked large lesions often appear from the leaf tip or edge on the leaves, and gradually turn brown. When it is wet, white mold grows on the edge of the lesions and the junction of healthy leaves. Lesions on the fruit are irregular and cloudy with fuzzy edges. When wet, a small amount of white mold grows on it. The lesions on the stem are dark brown, slightly sunken, and white mold is more prominent on the edge. The pathogen of this disease is a kind of fungus, and the white mold on the lesions is exactly the cyst peduncle and sporangia of the fungus. The primary source of infection came from diseased potato plants in the field.
Prevention methods:
①Strengthen cultivation management, deep ditch and high chamber, timely pruning and branching, and pay attention to ventilation and light transmission.
②Strengthen monitoring and reporting, eliminate central diseased plants in time, remove diseased leaves and fruits immediately when diseased plants are found, and spray pesticides to surrounding plants to prevent the disease from spreading. In the future, focus or comprehensive spraying can be used according to the disease condition, and can be used in turn 1 : 0.5: 200-250 times of Bordeaux mixture, 600-800 times of Swiss poison copper, 400-500 times of anti-virus alum for prevention and control, and respray in case of rain. Once every 7 to 10 days, continuous spraying 3 to 4 times.
Expert Tips:
The difference between tomato early blight and late blight mainly has the following points:
①The onset temperature is different. Late blight is prone to disease when the temperature is below 15°C and the relative humidity is 80%. Early blight is prone to disease when the temperature is lower than 25°C and the relative humidity is 85%.
② Leaf symptoms are different. Late blight starts from the tip or edge of the lower part of the plant, and initially becomes dark green and irregular water-stained shape, and then turns brown after expanding. Early blight: The lower leaves of the plant initially appear as pinpoint black spots, which later develop into ring spots and expand upwards.
③The symptoms of stems are different. Late blight: Lesions are long strips of dark brown, and white sparse and dense things sometimes grow on the edge. Early blight: Lesions are oval or diamond-shaped, dark brown.
④ There are differences in fruit symptoms. Late blight: It mainly occurs on green fruits, and the lesions are dark green in oil at first, and then turn brown in irregular moiré shape. The diseased fruit is hard and somewhat uneven. When the humidity is high, a small amount of white mold rots quickly, and the fruit generally does not fall off. Early blight: mainly occurs before the green fruit, and the lesions are oval or irregular brown or dark brown sunken spots. In the later stage, the fruit cracks, the diseased part is hard, and the black mold layer is densely grown.
