Occurrence and prevention of late blight in greenhouse tomatoes

Symptoms identify tomato late blight mainly affecting the leaves and stems of plants. The leaf is often covered with leaf tips and leaf margins. The lesions are dark green water-immersed, gradually dark brown, and the diseased junction is light green. When wet, white mold is produced at the junction of the back corridor. The stalk lesions are dark brown spots with unclear edges and slight depressions. There are white molds in the wet period; the disease spots are irregular gray-green oil-like hard plaques, and a small amount of white mold on the edges, which rapidly decays.
Prevention and control technology Agricultural control: strengthen field management, rational close planting, so that the ventilation and light transmission between the plants is good, pay attention to ventilation and ventilation in the shed.
2. Chemical control: Immediately after the emergence of the central diseased plant, spray protection. Optional 25% metalaxyl 800 times solution, or 64% anti-virus 矾 500 times solution, or 25% chlorothalonil 800 times solution alternately, interval 5 to 7 days, for 3 to 4 days. After watering, use 10% chlorothalonil smoke agent 300g per acre, or 72% grams of anti-gelable WP 600-800 times liquid spray, or 50% chlorothalonil dust 1 kg per acre.
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