The damping-off disease is one of the most serious diseases in the seedlings of melons, crucifers, eggplants, legumes, celery, etc., which are often the most serious diseases in the seedling stage. They occur in all parts of the country, causing great losses. 2. Onset of pathogens The oocysts and mycelia were overwintered in sick bodies, soil and humus. In areas protected by nursery and warm weather throughout the year, the disease can occur throughout the year. Mainly through the sick and residual body, soil, rain, irrigation, farm tools, workers shoes, watering and unfamiliar farmyard fertilizers spread. Seedbed soil moisture, temperature 15 ~ 18 °C, seedling growth is weak, the spring cold weather for many times, the occurrence of the disease more and heavy; heavy seedling seedling bed, old seedbed, old bed soil seedlings, will increase the incidence; high temperature, high humidity and flickering The hot weather is most conducive to the onset of disease; excessive seeding, excessive seedlings, leggy seedlings, poor air and light transmission, and seedlings lack of hardening seedlings will also trigger and aggravate the disease. 1 seedbed selection. To choose leeward sunny, high terrain, convenient irrigation and drainage, soil fertility, not planted vegetables or cultivated fruit seedlings in the field to do seedbeds, with ponds and mud and other disease-free new soil bed soil. 2 Grafting and soaking. Cucumber and zucchini selection of black pumpkin seeds, watermelon selection Chaofeng F1, pumpkin selection melon, eggplant selection of red eggplant and other resistant rootstock grafted cultivation, have a certain degree of disease prevention, disease resistance. The seeds were immersed in hot water at 55°C for 10 minutes, after which the water temperature was gradually reduced to about 30°C and soaking was continued for 1 to 2 hours. For seeds that are difficult to absorb, such as watermelons and melons, they are first immersed in cold water, and then soaked in hot water at 80-90°C (dip water while stirring in one direction) to reduce the water temperature to 70-75°C. Hold for 1 to 2 minutes, then pour cold water, so that the water temperature dropped to 20 ~ 30 °C, soaking for 4 to 5 hours. 3 Strengthen seedling management. Specific measures include the following: First, the application of fully cooked farmyard fertilizers. The second is not string irrigation or flood irrigation, with deep groundwater drip irrigation or hole irrigation. The third is the high-temperature sunny days and the cold winter, the bed soil is ploughed and exposed (frozen), which can reduce the incidence; in the nursery, the ventilation pipe is buried, and the surface is covered with a thick plastic film, then steam is used to prevent and control. The effects of soil-borne diseases such as damping-off disease can reach 95% or more. Fourthly, seed thinning should be appropriately diluted to improve the ventilation and light conditions of the seedbed, attach importance to the dehumidification of greenhouses and seedbeds, and plan the cultivation of seedlings, and control the amount of nitrogen fertilizer, which has a certain effect on the prevention and control of diseases. Fifth, bed soil surface is covered with one layer of fresh and dry grass ash or fresh dry grass ash is applied when bed soil is wet, which can inhibit or reduce the incidence. Sixth, spray several 0.1% to 0.2% potassium dihydrogen phosphate solution at the seedling stage to enhance the disease resistance of seedlings. Seventhly, the diseased seedlings and their nearby beds should be cleared in time, and fresh lime powder or dried fresh grass ash should be applied as soon as possible. 1 seed treatment. a. Any of a variety of dry weights, such as 70% Dukessible WP, 50% carbendazim WP, 50% thiram WP, and 65% zeocin WP, etc., with a seed dry weight of 0.2% to 0.3%. Mix the soaked seeds. b. Soaking with 40% formalin 100-fold solution for 20-30 minutes, or soaking with 1% copper sulfate for 5 minutes, or soaking with 50% agent-water 500 times for 15-30 minutes, or 500 times for 401 antibacterial agent Liquid soaking for 15 to 30 minutes, etc., and then picked up and rinsed with water 1 to 2 times. 2 soil treatment. A. Seed bed sprinkling 2% to 3% ammonia water (8 to 10 liters per square meter), and then covered with a plastic film, 5 to 6 days after uncovering the film and cultivating the bed soil, the ammonia smell can be sown. b. Each square meter of bed soil is sprayed on the bedtop with water of 80 times 40% formaldehyde solution for 80 times, and then covered with a plastic film. After 4 to 5 days, the film is uncovered and turned over 2 or 3 times. After drying for 10 days, it can be sowed. c. Use 25% metalaxyl wettable powder 5g and 50% carbendazim wettable powder 5g per square meter seedbed, add 10 ~ 15kg semi-dry semi-wet soil, mix and mix to make medicine. earth. Then, before the bottom water is poured on the seedbed, about 1/3 of the soil is spread on the bed surface (about 0.3 cm in thickness) and soaked with the remaining 2/3 of the soil. Medicinal soil is evenly sprinkled in the tillage layer, and the rest is used as a cover species. d. Evenly spread the seedbed per square meter with Green Hunter No. 1 (xymycin) 3000 times liquid. e. Mix green hen No. 1 2 to 3 grams and 10 to 20 kilograms of fine soil, mix well with 1 cubic meter of nutrient soil, and then insert the seedling tray or nursery seedlings; 3 to 5 liters, evenly sprayed on nutritious soil, mix well and use. 3 seedling control. The key is to spray medicine at the early stage of the disease, and the sooner the effect is, the better. a. Spray one of the following: 58% Leidomil 400 to 600 times, 25% 500 to 800 times, 64% to 400 to 600 times, 75% to 15% enemy powder Liquid, 58% Metalaxyl Manganese Zinc Wettable Powder 1000x, 50% Dysonammon 1000x Liquid, 50% Carbendazim 1000x, 75% Chlorothycetin Wettable Powder 800x, 25% Methyl Cream Ling WP 800 times, 72.2% Proccel 600 ~ 800 times, every 3 to 5 days spray 1, even spray 2 or 3 times, have better control effect. b. In the initial stage of disease or when the dead seedlings appear, spray soil or root with green hengheng No. 1 3000-4000 times solution or green hengheng No. 2 600-800 times solution. c. When watermelons, melons, eggplants, etc., become infected after field planting, the roots and surrounding soil of the diseased seedlings can be poured with 7% enemy pine 1000 times liquid, with 0.25 liters per plant. Dentist Light,Dental Headlight,Dental Loupe Light,Led Curing Light Dental Suzhou Escomedical Equipment Co.,Ltd , https://www.escodental.com
I. Disease occurrence
1. Symptoms of the disease The disease is caused by Pythium spp. The pathogens are highly sarcoid and can survive long-term in soil and diseased bodies. Seedling stem base near the base of the disease, the initial appearance of water-stained lesions, like boiling water burned like, and then into a brownish rotten, dry and around the stem 1 circle, resulting in the young stem after contracture lodging. When the environmental conditions are appropriate, it takes only about 1 day from the onset to the lodging of the seedlings, so it is called damping-off disease. The leaves of most of the diseased seedlings can remain green within 2 to 3 days, and they look like healthy seedlings, but they will soon lose water and die. Some seedlings will become infected before unearthing, resulting in bad species, bad shoots and lack of seedlings. The disease spreads extremely fast. In the initial stage, only individual seedlings in the seedbed became ill. Two to four days later, the diseased seedlings spread as the center, and a series of seedlings stumbled. At low temperature and high humidity, a white flocculent mycelium grows on the surface of the diseased seedlings and surrounding bed soil. The roots of the diseased seedlings are dark brown and soon rot.
Second, comprehensive prevention and control technology
1. Agricultural control measures
2. Method of chemical control