Scallion mildew disease and prevention measures
Onion planting process, there is a more serious disease, downy mildew is due to this disease will cause onion leaves a large area of ​​dead or dry, resulting in onion production has been reduced, so prevention and treatment of onion downy mildew is growing The people are most concerned about. Now Xiaobian talks about the disease of downy mildew and its prevention and treatment measures.
Symptoms of green onion downy mildew
First, the pathogen
The pathogen is a genus onion, which is a fungus disease.
Second, the law of incidence
The pathogens overwinter with the diseased plant residues in the soil or in the seedlings and bulbs. In the second year, it is spread by air, rain or insects. The best onset temperature of downy mildew is within 10-15 degrees, especially in humid and low temperature environment. When the soil is sticky, the drainage performance is not good, and the weather is rainy and foggy, when the plant grows poorly, the downy mildew is particularly serious.
Third, the symptoms of the disease
1. The diseased onion plants will stop growing and the plant height will decrease.
2, the blade will be thickened, and it will turn yellow and bend.
3, in the rainy season of spring and autumn, white mold layer will be formed, and the leaves will turn yellow and wither.
4, re-infected green onions, leaves and pedicels will appear yellow-white long oval large lesions, there will be white mildew on the surface, then turn green or dark purple, when the color will turn pale yellow, then slowly withered to death .
5, after the onion disease spots produce bacteria, sometimes also form a black velvet mold layer.
Control measures for downy mildew
1. When selecting seeds, choose varieties with strong disease resistance.
2. Choose a field plant with high dryness, ventilation and good drainage performance.
3. Apply sufficient base fertilizer and increase phosphorus and potassium fertilizer to improve the disease resistance of the plant.
4. The best drainage measures should be drained in time after rain to reduce the humidity in the field.
5, timely watering, reasonable watering, do not appear water accumulation.
6. Remove the residue of the diseased plant in time, concentrate it, burn it or bury it in a place far away from the field, and reduce the source of the disease.
7, the implementation of 2-3 years of rotation, sorghum high ridge cultivation, regular loose soil, etc., can alleviate the disease.
8. In the early stage of the disease, spray 20% thiabendone suspension 500 times solution, or 25% azoxystrobin suspension 1500 times solution, or 68.75% creamer salt · fluopyram suspension 800 times solution, or 60 % pyraclostrobin, dexamethasone dispersible granule 1000 times solution, or 76% propyl zinc, cream urinary cyanide wettable powder 800 to 1000 times solution, or 68% refined nail cream · manganese zinc water dispersion 600 times solution, or 69% manganese zinc, enoyl wettable powder 600 times solution, or 70% propsin zinc wettable powder 600 times solution, or 60% fluorine? manganese zinc wettable powder 1000 times solution, every Spray once every 7-10 days and spray two or three times in a row.
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