Tobacco wilt

Symptoms have increased in Shandong, Henan, Anhui, Fujian, Guizhou, and Taiwan. Seedling stage, adult stage can be the disease, generally in the long-term to budding stage symptoms are more obvious. Some were only on one side, with small leaves or main veins bent. The top of the diseased plant was bent to one side. The stems and roots of the disease were cut open, browning of the xylem was seen, hyphae or meristems could be seen near the discoloration of the diseased part of the microscope or near the catheter. spore. Later diseased plants gradually become yellow wilting and die.

The pathogen Fusarium oxysporum (Schlech) f.sp.nicotianae (Johns.) Snyder et Hansen called Fusarium oxysporum f. sp. Conidiophores grow on conidiophores, and conidia have large and small conidia types: small conidia are oblong, single cells are colorless, and a few twins are present. Large conidiophores were sickle-shaped, mostly 3 membranes, colorless, 354.2 (μm) in size, a few 4-5 membranes, and 44.34 (μm) in size, which produced chlamydospore and sclerotia. The host range is wider.

Transmission routes and pathogenic conditions The pathogens are mainly wintering in the body or in the soil with chlamydospore, and the survival period is as long as 8-10 years. When conditions are appropriate for the leap year, spore germination produces invading filaments that extend through the wound or directly through the elongate or meristematic regions of the root cells, extend to the xylem, colonize after being introduced into the tracheid or catheter, and can infect the xylem parenchyma . The bacteria produce pectin hydrolyzing enzymes, extracellular toxins, etc., causing the wilting or death of the strain. Temperature 28-31 °C susceptible to disease. The high-temperature sunny day and the sand land after the heavy rain in the late growth stage are responsible for its onset. The disease is a year-long epidemic disease. The initial infection determines the severity of the disease, and there is only one peak in the field.

Control methods (1) Selection of resistant varieties such as Nc95, Coker176, Nc567, Nc628, Burley 11A, Burley 11B, etc. In addition, T1448 is a high anti-anti-Fusarium wilt disease resistant to bacterial wilt. (2) Implement rotation for more than 5 years to promote grass crops or cotton rotations. However, Burley tobacco and dark smoke should not be rotated with cotton or sweet potatoes. (3) Advocate the use of compost or fermented organic fertilizer made from fermented bacteria. (4) Cultivate disease-free strong seedlings and, if necessary, seed bed disinfection. (5) pay attention to the prevention and treatment of nematodes can reduce the incidence. (6) Spray or water 50% carbendazim WP 400-500 times or 70% thiophanate-methyl WP 600 times, 50% benomyl WP 1000 times, 50 Praflurane WP can be 1000-1200 times liquid, and 400-500 ml of good liquid per plant should be filled with 2-3 times of irrigation.

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