First, the symptoms
Both the seedling stage and the adult plant stage can be affected. The incidence of disease at the adult stage is the most important and the damage is mainly caused by the leaves. The lesions were yellowish-green at the beginning, with no obvious margins, and later expanded with limited polygonal veins. The white surface of the leaves grows white mold. The disease first began to occur from the lower leaf, gradually spreading upwards, and later lesions became yellowish-brown, often with multiple lesions lining together, causing the leaves to dry up.
Second, transmission routes and conditions
The pathogens leave the mycelia and oospore left over in the field with the remnants of the diseased plants or lurking on the seeds. When the environmental conditions are appropriate, sporangia are produced and transmitted to the host plant by rain backsplash, air flow and insects, directly invading the epidermis of the host leaves, causing initial infection. The lesions appear after infection, and sporangia are produced in the affected parts. Repeated infestation by airflow propagation increases the hazard.
The pathogenic bacteria prefers low-temperature and high-humidity environments, suitable disease temperature range of 1 to 19°C, optimal disease environment, temperature of 15°C to 17°C, relative humidity of more than 90%, optimal disease-affecting development period of adult plants, and disease incubation period 3 to 5 days.
Third, control methods
1, choose resistant varieties.
2. Passport rotation: The re-emergence plots promote the rotation of grass crops for 2 to 3 years to reduce the source of field germs.
3, drug seed dressing. The choice of 30% Rhizoctonia or 25% Metalaxyl, the dose of 0.3-0.4% of the seed weight.
4, strengthen management. Reasonable dense planting, reasonable fertilizer, enhanced ventilation and light transmission in the field, drainage of the ditch, reduction of the humidity in the field, promotion of plant robustness, and improvement of disease resistance of the plants; removal of diseased bodies after harvest, bringing out concentrated destruction of fields, deep soiling, accelerated disease Decomposition of debris.
5, chemical control: In the initial stage of onset of spraying, medication interval of 7 to 10 days, continuous spray control 2 to 3 times. The agent can be used 58% metalaxyl MnZn WP 500 times; 70% 100% WP WP 600 times; 75% chlorothalonil WP 700 times; 72% WP WP 800 times Liquid and so on.
YT-88
YT-88
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