Onion is a common crop in agricultural planting. Due to some unpredictable diseases, various problems occur in planting. Not only the onion yield is reduced, but also the cost of planters is increased. Today, Xiaobian talks about the symptoms of leaf blight and its control measures during the process of growing onions.
First, the symptoms of onion leaf blight
1, the pathogen
The pathogen is an asexual black mold fungus, belonging to the subfamily Fungus. It has a sexual state of Ascomycetes, belonging to the Ascomycetes subfamily fungus.
2, the law of incidence
The pathogens overwinter in the soil with the diseased plant residues. In the following year, by airflow, the pathogen is a weak parasitic bacteria, which is not easy to infect healthy plants, often accompanied by downy mildew and purple spot disease.
3, the symptoms of the disease
The disease mainly occurs on the leaves and flower buds. At the beginning of the disease, the leaves begin to appear. The lesions appear white round spots, gradually expanding, and the color changes to grayish yellow to taupe, the shape is not uniform, the size is different, and sometimes the whole blade. The diseased spot is densely black with mildew, and the lesion is gray or light yellow after the mold is scattered. Finally, small black spots (ie, ascospores) are produced on the lesion. As the lesions enlarge, the leaves curl, the leaves and flower buds turn yellow and die, or break from the diseased part. When the damage is serious, the garlic is not easy to convulsion.
Second, onion leaf blight prevention and control measures
1. Do field management, remove the diseased diseased leaves and diseased stalks in time, and remove them and bury them in the field or burn them.
2. After harvesting the green onions, it is necessary to remove the diseased branches in the field in time to carry out concentrated burning, which can reduce the reproduction of the source of the bacteria in the field.
3, reasonable close planting, facilitate plant ventilation, light, reduce bacterial infection.
4, Shiji fertilizer, must be decomposed farmyard manure, at the same time to increase the application of organic fertilizer, which is conducive to improve the disease resistance of plants.
5, reasonable watering, in the rainy weather to do a good job of drainage, reduce the humidity in the field, this can effectively avoid the disease environment conditions.
6, in the early stage of onion leaf blight, you can use 70% mancozeb WP 500 times solution, or 75% chlorothalonil WP 600 times solution, or 40% azoxystrobin phenyl ether suspension 1500- 2000 times liquid, or 2.5% phoricidin suspension 1200 times solution, or 10% polymycin-resistant B wettable powder 800-1000 times solution, or 25% azoxystrobin suspension agent l500 times solution, alternately used, every Use the medicine once every ten days and spray it two or three times in a row. It is also possible to use a protective agent. In the early stage of the disease, 10% Shiga granules 1500-2000 times solution, or 25% Shibao emulsifiable oil 1000 times solution, or 58% metalaxyl Mn-Zn wettable powder 500 times solution are used. Spray control, spraying the agent once every 7-10 days, spraying two or three times in a row, is effective for the prevention and control of leaf blight, and can make the onion grow normally.
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