Control technology of white silk disease

White silk disease, also known as sclerotial root rot and sclerotial seedling blight, harms the roots and stems of seedlings and young trees, mainly harms Camellia oleifera, paulownia, catalpa, citrus, apple, sycamore, paulownia, walnut, Masson pine and other tree species, and can also cause peanuts, green onions and many other crops, mainly distributed in the south and southwest of Henan Province. Let's take a look at the prevention and control techniques of white silk disease.

Symptoms of white silk disease

White silk disease usually occurs in the root stem or the base of the stem of the seedling, and the cortex of the susceptible root stem gradually turns brown necrotic, with severe cortical decay. After the seedlings were damaged, it affected the absorption of water and nutrients, resulting in poor growth, the aboveground leaves became smaller and yellowed, the internodes of the branches were shortened, and the branches and leaves withered seriously, and the whole plant withered after one week of the disease spot. Under wet conditions, the damaged rhizome surface or near-ground soil surface was covered with white silk mycelium. In the later stage, many rapeseed-like small sclerotia were formed in the mycelium, which were white at first, then gradually changed from yellowish to yellowish brown, and then became tea-brown. The hyphae gradually extend downward to the roots, causing root rot. The leaves of some tree species are also susceptible to disease, with brown ring-shaped disease spots and small sclerotia growing on the diseased leaves.

The pathogen of white silk disease

The asexual generation of the pathogen causing white silk disease of trees is Sclerotinia uniformis. The optimum temperature for the development of Alternaria alternata was 30 ℃, the highest was about 40 ℃, and the lowest was 10 ℃. It could grow at pH 1.9 to 8.4. PH5.9 was the most suitable for reproduction, and light could promote sclerotia production. Sclerotia will germinate under suitable conditions, no dormancy period, can dormancy under bad conditions, sclerotia can survive in soil for 5-6 years, and survive longer under low temperature and dry conditions.

Prevention and treatment of White Silk Disease

1. Nursery site selection: nursery land should be selected with fertile soil, loose soil and good drainage. The nursery with serious disease of the previous crop should be rotated with Gramineae crops for more than 4 years before it can be replanted.

2. Deep ploughing in winter: in the susceptible nursery, deep ploughing should be carried out every winter to bury the remains of diseased plants in the soil to remove the source of infection.

3. Soil disinfection: before raising seedlings or afforestation, 1000 grams of pentachloronitrobenzene wettable powder per mu and 20 kilograms of fine soil should be mixed and scattered evenly in the sowing ditch or around the tree holes. For lightly susceptible seedlings, you can dig up the soil at the rhizome, dry the rhizome for several days or spread quicklime to disinfect the soil.

4. strengthen management: timely fertilization, watering, drainage and weeding should be carried out during the seedling growing period, so as to promote the vigorous growth of seedlings and improve the disease resistance of seedlings. In summer, it is necessary to protect against sun exposure, reduce the harm of burns, and reduce the chances of bacterial infection.

5. Chemical control: at the initial stage of the disease, Fengqian Genbao can be used 600 times or 800 times or 1% copper sulfate solution can be used to irrigate the roots of diseased plants, or 50 grams of 25% verapamil wettable powder and 50 kg of water can be used to irrigate the roots of diseased plants, or 50 ml of 20% methyl parathion EC can be used per mu, 50 kg of water can be added, and sprayed every 10 days or so.