Chinese cabbage leaf rot symptoms
Only the leaves are damaged, and the damaged leaves are initially watery and wet rot. The lesions are irregular after expansion. Under wet conditions, the diseased parts are grayish green and become grayish white when dry. In continuous rainy weather, the disease spreads quickly, and the whole leaf or even the whole plant leaves rot, leaving only the main vein and the more complete petiole. Under humid conditions, the filamentous mycelium can be seen in the wet rot, and then gradually tangled to form a brown sclerotium sclerotium.
The pathogenesis of Chinese cabbage leaf rot
The pathogen is overwintered in the soil by the mycelium in the diseased part or by the sclerotia. The conditions of the leap year are suitable, the hyphae of the wintering grows, the hyphae grow out of the sclerotia, and the mycelium contacts the leaf tissue and infects it. After the onset of the vegetable leaf, the mycelium on the diseased part spreads and spreads to the nearby leaves and surrounding vegetable plants by contact or climbing, causing the disease to occur in the field, and the condition continues to expand. The pathogen can develop in the range of 10-38 Â° C, and the optimum temperature is 28-32 Â° C. When the sclerotium is at 27-30 Â° C and has sufficient humidity, the hyphae can grow out within 1-2 days, and a new sclerotium can be formed in 6-10 days. Light conditions have a stimulating effect on sclerotia formation. High temperature and high humidity weather and frequent typhoon or rain seasons, or low-lying terrain and planting too dense and partial application of nitrogen fertilizers.
Chinese cabbage leaf rot prevention and control measures
1. Agricultural measures
1 Avoid planting Chinese cabbage in severe plots of rice or soybean sheath blight.
2 Strengthen the management of fertilizer and water, avoid partial application of nitrogen fertilizer, increase the application of phosphorus and potassium fertilizer, moderate watering, and avoid excessive humidity in the field. Early detection and removal of central diseased plants, burning or deep burial.
3 timely spraying of phytochemicals and other growth promoters to promote early growth of the plant.
2, chemical control
In the early stage of the disease, it can be sprayed with 14% solution of lysine copper water solution 350 times, or 3% jinggangmycin water 2000 times solution, or 40% zephyr WP 1000 times solution, once every 7 days. Continuous control 2-3 times.
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