Symptoms
The disease mainly damages the leaves and petioles. It grows as pale yellow dots on the leaves, and gradually expands into round or oval grayish-brown lesions. It is rim-like and has small black spots at the center. In severe cases, the diseased leaves will fade early.
The law of incidence
The disease is a fungal disease. The pathogenic spores are transmitted by wind and rain. When the spores germinate, they produce germ tubes that invade directly from the wound or penetrating the epidermis. After a few days of incubation, they begin to produce conidia and conidia. Reinfection. Low-lying terrain, excessive planting density, moist air and little rain are all conducive to the disease.
Control methods
1. Use resistant varieties. Planted early-maturing hybrids such as the Bosch hybrid No.9 and the Bosch hybrid No.10.
2. Warm soup soaking. Before sowing, the seeds were soaked in warm water of 52°C for 20 minutes, continuously stirred, and then moved into cold water to cool, dry, and sow.
3. Agricultural measures. More than 3 years of rotation with other vegetables. Proper close planting to improve ventilation and light transmission conditions between plants. Release the air in a timely manner to reduce the humidity in the shed. When watering, it is necessary to dilute the water and prevent flooding. When fertilizing, pay attention to the reasonable ratio of nitrogen, phosphorus and potassium, and strictly prohibit the excessive application of nitrogen fertilizer. After harvesting, we must clean the pastoral areas in time, and take the sickness out of the greenhouse, burn it or bury it deeply.
4. Chemical control. Spray 50% Carbendazim WP 700 times, 80% Anthraquinone WP WP 800 times, or 50% thiophanate-methyl WP 500 times, or 25% TC WP. 500 times liquid powder, or 30% green leaf Dan wettable powder 600 times, sprayed every 7 days, continuous spray 2 or 3 times. The above pesticides can be used interchangeably to avoid drug resistance.
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