symptom
Leaf lesions are round, pale brown or dark brown, 4 to 6 mm in diameter or larger, with distinct concentric patterns and sometimes a yellow halo on the edges. 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.
Law of onset
The pathogen is mainly spread by mycelium or conidia on the sick body or seed by means of wind and rain. The pathogen can grow and develop in the range of 10 °C ~ 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. The terrain is low, the management is extensive, the lack of water and fertilizer, the plant growth is poor, the disease resistance is weak, and the general incidence is heavy.
Control method
Seed disinfection
Seeds were left on the disease-free plants, or the seeds were soaked in warm water at 50 ° C for 25 minutes, then immediately transferred to cold water, and then the seeds were taken out and dried for sowing. 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%.
Strengthen management
Rotation is carried out to apply the base fertilizer, but it is necessary to apply the high-quality organic fertilizer that has been decomposed, and to increase the application of phosphorus and potassium fertilizer. Where there are conditions, formula fertilization can be used to make the plant grow better and 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.
Chemical control
In the early stage of the disease, 50% phorhin WP 1000 times solution, or 50% carbendazim WP 800 times solution, or 50% thiram double WP 500 times solution, or 40% sterilized Dan WP 400 times solution, or 64% anti-virus WP WP 500 times solution, or 50% keeling WP 1000 times solution, or 70% mancozeb WP 400 times solution, spray every 7 days 1 time, even spray 3 to 4 times.
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