Control and identification of white silk disease of Populus tomentosa

The occurrence of white silk disease of Populus tomentosa is caused by fungi, which is destructive and spreads rapidly. if it is not controlled, it may lead to the death of all seedlings. According to the previous work, we summarized the characteristics and control methods of white silk disease of Euonymus tomentosa.

Symptoms: at the beginning of the disease, the stem or leaf base turned brown and rotted near the soil, and after several days of sunlight exposure, white silk-like mycelium appeared on the disease part and soil surface, which spread radially in the rhizosphere soil, and brown grew on the near-surface stem in the later stage. Rapeseed sclerotia, often causing death of the whole plant. The leaves showed that the leaves first darkened and then lost green and finally became yellow and dry.

The law of disease: the pathogen overwintered in the soil in the form of sclerotia (the bacteria had strong resistance to adverse environment and could survive in the soil for 5 to 6 years). In the second year, the sclerotia germinated and grew hyphae, spread in the soil, invaded from the base of the plant and caused the disease.

Disease conditions: acid soil is conducive to the disease (suitable pH range: 1.9 Mel 8.4, the optimum pH is 5.9); the environment of high temperature and humidity is conducive to the disease (serious in August and September), and the optimum growth temperature is 30 to 35 ℃; the disease is serious in continuous cropping soil (the soil contains many bacteria and survives for a long time); the disease in clayey soil is serious. Low-lying terrain, over-dense planting, poor ventilation and light transmittance of the disease is serious (bacteria like the condition of wet nest wind).

Prevention and control measures:

① strictly in and out of the seedling system, do not buy seedlings from the affected areas, to prevent man-made transmission of diseases.

② is a soil-borne disease, so soil sterilization is a key measure. 0.2% pentachloronitrobenzene or thiram can be mixed with the soil and planted, or 5 to 10 grams per square meter, with appropriate amount of fine soil sprinkled into the soil. Try to choose disease-free land when planting, and continuous cropping should be avoided.

The ③ plot should be basically flat. Began to control watering in May to keep the surface relatively dry and increase the application of phosphorus and potassium fertilizer. Pay attention to the rainy season drainage, sudden sunny after the rain, to drain the stagnant water step by step, not at once.

④ was sprayed with 1 ∶ 1 ∶ Bordeaux solution for protective prevention. At the initial stage of the disease, the disease can be sprayed with 50% carbendazim or 75% chlorothalonil combined with root irrigation or 2500 times of 25% enemy demulsifiable liquid spray, which has a special effect on the disease, valid for 5 weeks, efficient internal absorption, effective for 2 hours, and resistant to Rain Water erosion.

Ploughing and loosening the soil in time after ⑤ rain, and do a good job in the prevention and control of other diseases and insect pests.

The row spacing of ⑥ plant should not be too close, and the dense branches should be pruned in time. Remove the diseased leaf disease plants in time, remove the hyphae and sclerotia from the soil surface and burn them centrally, and disinfect the soil with fungicides in time.

⑦ does a good job of protecting sick and weak seedlings from cold in winter in the north.