Onion blight is one of the common diseases of onion, which is common in various vegetable areas, mainly affecting onion and garlic vegetables such as green onions, chives, onions and leeks.
Onion plague symptoms
Mainly harmful to leaves and pedicels. In the early stage of the disease, the lesions are dark green, water-soaked, and grayish white lesions after expansion, and the periphery is not obvious. After the leaves and peduncles lose water, the contractures become thinner, the leaves are withered, and the diseased parts are easy to fold. When the air humidity is high, the diseased part produces a white mold layer (that is, a spore sac and a spore stalk of the pathogen). When the weather is dry, the white mold layer disappears, and the inner wall of the diseased part of the leaf is peeled off, and the white hairy mildew layer (that is, the mycelium of the pathogen) is seen, which is different from the physiological dryness of the onion.
Onion disease characteristics
The disease is caused by the infection of the fungus Flagellum genus. The pathogens are left in the field with oospores, mycelia and chlamydospores. When the environmental conditions are suitable, sporangia and zoospores are produced, which are transmitted to the host plants by rainwater splashing or airflow. After the spores are germinated, the germ tubes are directly invaded from the host epidermis, causing the initial infection. The diseased department produces a new generation of sporangia, which is re-infected by wind and rain.
The pathogen prefers high temperature and high humidity environment. The most suitable environmental conditions for the disease are temperature of 25-32 ° C and relative humidity of over 90%. Therefore, the main onset of onion blight is from May to July. The optimal growth period is from adult to harvest.
Perennial continuous cropping, low-lying stagnant water or cultivated plants with high planting density, plant weakness and long-term application, and excessive application of nitrogen fertilizer have a serious incidence. In the years with more rainfall during the year, the incidence is heavy.
Onion disease prevention and control points
1 Implement rotation: Promote rotation with non-onion garlic vegetables to reduce the source of pathogens in the field.
2 Strengthen field management: deep ditch sorghum; reasonable close planting; clear water after rain. Ventilation and ventilation work should also be done in time to protect the field cultivation. After the harvest, the diseased bodies are removed in time, and the field is destroyed to reduce the pathogenic bacteria in the field; the soil is deeply turned over to accelerate the decomposition and decomposition of the diseased bodies.
3 chemical control: spraying at the beginning of the disease. The medicine can be selected by using 75% chlorothalonil 600 times liquid, etc., spray control. Spray once every 7 to 10 days and spray continuously for 2 to 3 times.
300mm (12 Inch) Flat Cut-off Disc
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