How to prevent seedling damping-off disease?

Seedling quenching disease is common in all parts of our country, which mainly harms all kinds of seedlings and flowers seedlings, which can lead to seedling death. So how to prevent and cure seedling seedling stunting disease?

1. Symptoms and causes of seedling quenching disease

1. Symptoms

The seeds or buds were infected and rotted when they were not unearthed, and the disease occurred at the seedling stage. The base of the stem on or below the surface showed watery disease spots, the diseased part was yellowish brown, constricted, and could expand to the upper and lower parts of the plant, showing a linear shape. The disease develops rapidly, the tissue disintegrates, and the young stems wilt and lodge, but the edges of the leaves are green in a short period of time. If the environment is wet, white woolly mold will grow on the soil surface of the diseased part and its vicinity.

2. Etiology

The pathogen is some fungi of Pythium. The common ones are Pythium and Debali Pythium. The lowest growth temperature of the two kinds of Pythium was 5 to 6 ℃, the optimum temperature was 26 to 28 ℃, and the highest temperature was 36 to 37 ℃. High humidity is easy to occur, and it is highly saprophytic, and it can rot on parasitic residues in the soil for 4 years. Pythium is a soil resident fungus, which is saprophytic for a long time in the soil and forms oospores to pass through the bad environment. It is a soil-borne disease, which is mainly caused by oospores in the soil, mycelium in the soil residue or other organic matter, mixed with compost and overwintering. The pathogen is mainly transmitted by water and human horticulture.

3. Morbidity condition

High humidity is the main condition of seedling disease. In the Yangtze River Basin of China, there is Meiyu in May and June, which is conducive to the growth, development and spread of bacteria, but not conducive to the growth of seedlings, resulting in the decline of disease resistance and aggravation of the disease.

In addition, lack of sunlight, continuous cropping, improper selection of nursery land (such as low-lying land, heavy clay, sudden disease and not thoroughly disinfected), poor quality of land preparation, application of compost mixed with pathogens without high temperature ripening, improper sowing will lead to the disease.

II. Prevention and treatment of seedling quenching disease

1. Choose a good nursery site

It is best to choose mountainous areas and newly reclaimed land to raise seedlings to avoid continuous cropping, there are few germs in the soil and the incidence of seedlings is light. If using cooked land to raise seedlings, it is better to use legumes or oak seedlings as the previous crops. The land between eggplant, melon, cotton, potato and other susceptible plants should not be used as nursery, or sowed and raised seedlings after disinfection. Do not choose a nursery where the groundwater level is too high or where the drainage is poor. If you raise seedlings in the nursery with poor drainage, you should open a good drainage ditch, make a higher seedling bed, and the bed surface is flat to avoid stagnant water.

2. Soil disinfection

In acid soil, combined with soil preparation, 20~25kg quicklime was sprinkled every 667m to inhibit the reproduction of bacteria in the soil and promote plant decay. In areas where firewood and grass are more convenient, the topsoil can also be burned to eliminate germs in the topsoil. Do not burn topsoil areas, you can use chemicals to treat the soil.

3. Mature fertilizer

Organic fertilizers, especially garbage compost and compost, often carry bacteria and should be used after accumulation, fermentation and full maturity.

4. Meticulous land preparation

The nursery should be ploughed deeply and carefully. Before sowing, put 1cm thick heart soil or burning soil in the sowing ditch, and after sowing, cover the seeds with heart soil or fire soil. Because the heart soil and burning soil do not carry bacteria, it can isolate the seeds from the bacteria, prevent the seed buds from rotting, protect the roots and stems of the seedlings from being attacked by the bacteria, and avoid the quenching disease of the seedlings. After the seedling grows up gradually, the cuticle and cork layer have been formed in the seedling stem, and the disease resistance is enhanced. Although root rot may still occur, it will not spread and cause disaster. The inner soil is easy to harden after rain, easy to crack in dry season, should not be too thick, and should not exceed 1.5cm. The thickness of the core soil seems to be hidden by the seeds.

5. Timely early sowing

Early sowing at the right time, early seed germination, deep root, strong growth and strong disease resistance. But sowing too early, low soil temperature, seeds can not germinate, seeds in the soil for too long, easy to seed bud rot. Sowing is too late, if you encounter Rain Water after the seedlings are unearthed, it is easy to have quenching disease.