High-efficiency prevention technology of onion purple spot

Onion purple spot disease is one of the main diseases that harm onions. It often causes disease on the onion neck. The diseased part shrinks and is prone to mold. The diseased spots are spindle-shaped and dark in color, which seriously affects the yield and quality of onion. The characteristics, hazards and effective control measures of onion purple spot disease are summarized as follows:

1. Symptoms of onion purple spot disease

Purple spot disease mainly affects onion leaves, pedicels and bulbs. The lesion begins with the tip of the leaf. The initial lesion is small, gray to light brown, with a slightly purple central color and a dark gray mold. The lesion rapidly expands into an elliptical or spindle shape, which is dark purple after depression, accompanied by concentric and yellow halos. When the humidity is high, the lesions will quickly expand to the whole leaf, often causing the onion leaves to turn yellow from the bottom to the top and even die, seriously affecting the yield and quality of the onion.

2. The pathogenesis of onion purple spot disease

In the cold regions of the north, the mycelium is overwintered in the host body or in the soil with the diseased body. In the next year, the mycelium will be conidia, and then spread by air or rain, and invaded through the stomata, wound or directly penetrate the epidermis. The onset temperature is 25 to 27 ° C, and less than 12 ° C does not occur. The spores of the pathogens need high humidity, and there are water droplets in the germination and intrusion, so the summer is more damaging in the climate. In addition, sandy soil, dry land, old seedlings, lack of fertilizer or thrips are serious diseases.

3. Prevention and treatment of onion purple spot disease

1 agricultural measures

Onion planting should be carried out for more than 2 years, and the base fertilizer should be applied during planting to enhance the disease resistance of the onion.

In particular, the onion should be harvested when the top of the onion is ripe. After drying, it can be dried until the outside of the bulb is dry. The temperature is controlled at 0 to 5 °C and the relative humidity is below 65%.

2 chemical control

Seeds should be soaked in 40% formaldehyde 300 times for 3 hours, washed in time after immersion. In the early stage of the disease, spray 75% chlorothalonil WP 600 times solution, or 64% antivirus WP WP 500 times solution, or 80% green Hensen manganese Zn 500 times solution, or 40% Dafudan 500 times solution. Or 50% of the 1500 times solution of chlorhexidine, or 2% of the multi-antimycin 30ppm, or 50% of the ketone 30-50 grams, or the onion and garlic bacteria and other agents spray.

Any one of the above agents may be used, and various agents should be used alternately, once every 7-10 days, and continuously controlled 3 times. Adding neutral detergent to the medicinal agent can increase the adhesion of the solution. It is recommended to add 5-10 grams of detergent powder per 10 kg.

3 comprehensive prevention

The prevention and treatment of onion purple spot disease needs to start from the clean field. Before the onion is planted, the field weeds, sick bodies and other infectious sources are completely removed, and the field is taken out to burn, and the whole garden is deep-turned and sprayed with disinfectant to effectively reduce the field. Residual pathogens.

After the seedlings are unearthed, the new high-fat film is sprayed at appropriate time to isolate the infection of the bacteria, improve the ability of the onion to resist natural disasters and the intensity of photosynthesis, and protect the onion seedlings from growing. Timely prevention and control of pests such as thrips in the field, avoiding plant wounds and reducing the infection rate of purple spot disease.

It is found that the symptoms of purple spot disease should be timely controlled by targeted drugs, and early control of onion purple spot disease. And pay attention to reduce the number of irrigation, in order to reduce soil moisture, and promote the onion to restore growth as soon as possible.

Finally, Hui Nongwang Xiaobian reminded everyone that understanding onion purple spot disease and correcting the prevention and treatment of onion purple spot disease can improve the yield and quality of onion.

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