The lettuce black spot disease can grow and develop in the range of 10-35 °C, and the optimum temperature is about 17 °C. High humidity is required, relative humidity is above 80%, and if the relative humidity is less than 75%, the incidence is generally mild or not. High humidity, low rain and low temperature are the key factors in the disease. The density is high, the terrain is low, the management is extensive, the water shortage is lack of fertilizer, the plant growth is poor, the disease resistance is weak, and the disease is generally heavy.
The leaf spot of lettuce black spot disease is round, and is limited by the leaf surface in the later stage, which is polygonal, brown or dark brown, and the size is uncertain. Black mold on the lesions when wet. When the disease is severe, the leaf lesions often converge, causing the leaves to die or the whole leaves to dry up.
First, the implementation of rotation with non-cruciferous vegetables for 2 years. Applying the base fertilizer, but applying the fertilized high-quality organic fertilizer, and adding phosphorus and potassium fertilizer, so that the plant grows well, can improve the disease resistance of the plant. Diseased leaves and diseased bodies should be removed from the field in time to be buried or burned.
Second, in the early stage of the disease, 50% phoraceous WP 1000 times solution, or 50% carbendazim WP 800 times solution, or 50% thiram double WP 500 times solution, or 40% sterilized Danke Wet powder 400 times solution, or 64% antivirus WP WP 500 times solution, or 50% keeling WP 1000 times solution, or 70% mancozeb WP 400 times solution, etc. Spray once a day, even spray 3-4 times.
3. Seeds are left on the disease-free plants, or the seeds are soaked in warm water at 50 ° C for 25 minutes, then immediately transferred to cold water, and then the seeds are taken out to dry and sow. It can also be seeded with 50% of the seed weight of 0.3% of the chlorhexidine wettable powder, or with 50% of the acesulfame powder of the seed weight of 0.4%.
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