In the early spring vegetables cultivation process, due to bad weather, diseases and improper management. Often cause the emergence of dead vegetables, severely affect the normal growth of vegetable seedlings. For this reason, according to the production practice experience, the causes of the dead vegetables and the control measures are introduced for reference. First, the reason 1. The diseases caused by the dead seedlings caused by diseases caused the death of the seedlings in early spring, mainly including damping-off, damping-off, and gray mold. The culprit dead can occur throughout the seedling stage. At the time of onset, water-stained dark lesions at the base of the young stems spread around the stem for 1 week, and the diseased part mostly showed atrophy, dry depression, and lodging on the ground. The reason is that seeds, soil with germs, high temperature and humidity, seedlings are too dense and long. Blight dead seedlings generally occur in late seedlings. At the time of onset, the base of the seedling stem produced an oval-shaped dark brown spot. The diseased seedlings began to wilt during the day and returned to normal at night. As the disease progressed, the lesions spread around the stem for 1 week, and the depression and shrinkage caused the dead seedlings to stand upright. The reason is due to high temperature, high humidity and continuous farming. Blast mold dead seedlings and adult plants can occur. At the early stage of disease, the tip of the cotyledon begins to yellow, and then spreads to the young stem, resulting in contraction of the stem, often resulting in the death of the diseased part. The brown stem is initially produced on the stem of the adult plant, and the upper surface of the diseased part of the disease is caused by the gray mold. Leaves fall off. The reason is due to low temperature and high temperature, poor ventilation, etc. 2. Symptoms of dead seedlings caused by freezing injury are that the leaves curl inward from the tip and gradually lose their water and dry tips. The leaves are white and the leaves are dry. The main reason is the sudden change of weather. When cold air invades the nursery bed, the convection of cold air or excessive release of the film is excessive, and the cold and hot air inside and outside the seedbed changes too much. 3. Dead seedlings caused by improper management are also known as bored seedlings. Symptoms showed that the upper part of the seedlings was boiled and drooping, not discolored, and then died of dryness. The main reason is long-term rain, seedlings can not be ventilated for a long time, the light time is less, the seedlings grow in low temperature, high humidity, low light conditions, nutrient consumption is too large, can not adapt to changes in temperature, humidity, light after a sudden sunny weather Caused. Second, the prevention and control measures 1. For the dead seedlings caused by disease, seed disinfection should be done before sowing. Generally, every kilogram of seeds can be green seeded 3-4 gram seed dressing or per kilogram seeds with green hen No. 2 2-4 grams diffuse species 10 to 20 minutes, in particular bed soil disinfection, 50% more bacteria can be used per square meter Ling WP or 50% pentachloronitrobenzene powder 8-10 grams or Green Hunter 2 3-4 grams mix well with sieving fine dry soil, spread 1/3 of the drug soil on the seedbed, sowing After 2/3 of the medicine soil as cover soil. After the onset of disease, a small number of diseased plants were found to be timely and deeply buried, and 75% of chlorothalonil wettable powder 600 times, 58% of Lei Duomier WP or 500 times of Green Hunter 2 were sprayed at the same time. One day spray, spray 2-3 times. 2. For the dead seedlings caused by frost damage and improper management, we must strengthen the management of seedbeds and carefully carry out the work of heat preservation, dehumidification, and ventilation and light transmission. Do not suddenly remove the film and vent the air. The ventilation of the uncovered film shall be gradually carried out to prevent the convection of cold air during ventilation. In case of cold air invasion, warming and insulation work should be done. Long-term rain should be drained in time for drainage and dehumidification. After the eye is exposed, ventilation should be strengthened to maintain proper temperature and humidity. Generally, it should be kept at 20-25°C during the day and 12-15°C during the night to prevent high temperature, high humidity or low temperature. wet.
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