Occurrence and Control of Garlic Sclerotinia

I. Symptoms and Pathogens The disease mainly damages the base of garlic pseudostems, and the initial diseased area is water-stained. Afterwards, the lesions turn darker or grayish, and the stains rot and the rotten parts emit a strong garlic odor. When the humidity is high, white cotton-like mycelium grows on the surface, so that the weeds around the diseased plants are also covered with white hyphae and ulcers rot. After the rot of the garlic leaf sheath, the upper leaves showed wilting, and gradually yellowed and died, garlic roots, root discs rotted, and garlic heads were scattered. Generally after the beginning of May, the diseased part did not plan to have dark brown sclerotia like hemp seed size. The disease is caused by the infection of S. sakazakii. Second, the law of occurrence (a) the cycle of infection Garlic sclerotinia mainly sclerotial nucleus left in the soil or mixed with the garlic species and the sick body over the summer or winter. The sclerotia mixed with garlic and diseased bodies fall into the soil with sowing and fertilization. In the early years of sowing, a few sclerotia will germinate in the fall and cause seedling disease. Generally in the late spring of February, the sclerotia in the soil will successively produce the ascitium plate. The ascospores will emerge from the ascus after maturation and invade the base of the pseudostem to form the mycelium. In the process of its metabolism, pectinase is produced, which dissolves the mesangial layer of host cells and causes the diseased stems to rot. Afterwards, the mycelium spreads and spreads from the diseased part to the periphery. Finally, sclerotia are formed on the diseased tissue and fall into the soil with the harvest. Or stay on the garlic for the second year of infestation. (b) Factors affecting the occurrence of diseases 1. temperature humidity. The bacteria likes low temperature and high humidity, generally the temperature is 15°C-20°C and the relative humidity is more than 85%, which is conducive to the germination of sclerotia and the growth and invasion of mycelia. Due to the use of mulch film coverage, long-term maintenance of high temperature under the membrane (relative to humidity greater than 80%) is conducive to the occurrence of Sclerotinia, which is one of the main factors that caused this disease to increase year by year in our county. In the local area, sowing of early years or plots can occur before winter. For example, in October 1996, the average temperature was 15.6°C, which was close to normal, and the average temperature in early November was 1.45°C and 1.23°C lower than the same period of the previous year, respectively. 11 On the 26th of the month, the spot was observed on the spotted plot; in October 1997, the average temperature was 1.75°C higher than normal, and it was 0.85°C higher in the first half of November. On November 19th, the spot was found on the designated plot. Most sclerotia germinate after a year. When the average temperature in late February to early March passes 6°C, the sclerotia in the soil will generate beamlets in succession. When the temperature rises to 13°C-14°C in early April, it will form the first one. Infestation peak. Spring rainy weather often aggravates the progression of the disease. 2. Rotation, continuous cropping. In the continuous cropping site, sclerotia has fallen in the soil and accumulated year after year, resulting in severe disease. Rotation can reduce the accumulation of bacterial sources in the field, especially in wheat rotation. Since the bacterium caused by Sclerotinia sclerotiorum does not infect wheat, the sclerotia are not suitable after germination. The environment can not complete the cycle of infection, thus reducing the incidence. Tests have shown that the average disease rate of the old garlic crops that have been cultivating wheat for one year in a five-year rotation is 18.6% lower than that for the six-year old garlic plot, and the disease index is 11.1 less. 3. Film coating method. In 1997, we chose to conduct tests on a re-emerging plot year-round. It was proved that the incidence of the most severely covered garlic, autumn covered with spring film on April 15 followed by garlic, and the incidence of garlic was the lightest. However, the production test showed that in the spring, the uncovered garlic and open field garlic were 7.8% and 25% lower than the coated garlic, respectively. The effect of the uncovered garlic on the yield exceeded the damage damage of the disease, so the uncovered film could not be used as a control. Measures. 4. terrain. Low-lying terrain, poor drainage, and low-lying land near the river are more serious. Third, comprehensive control measures 1. Rotation is down. It is best to plant 2-3 years of garlic rotation wheat for 1 year, and the longest continuous crop should not exceed 5 years. 2. Select healthy and disease-free garlic seeds. 3. Harvest into the timely removal of residues of garlic disease, brought deep outside the field. 4. Timely sowing, reasonable dense planting, adequate base fertilizer, so that a reasonable ratio of organic fertilizer, nitrogen, phosphorus, potash fertilizer, the general base fertilizer applied more than 5000kg organic fertilizer, high-quality garlic compound fertilizer 150kg. Planting density is controlled at 23000-24000 plants per acre. 5. In autumn, 50% carbendazim powder or 70% thiophanate-methyl powder is used, and the seeds are uniformly sprayed with water in an amount of 0.3% of the seed amount. The seed is boring for 5 hours, and then sown after drying. 6. When the onset of spring in early spring, generally in late March, with 50% speed Keling powder 1500 times, or 50% Carbendazim 500 times spray control, spraying the base of the stem, spraying once every 7-10d Continuous prevention and treatment 2-3 times.

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