Recently, reader Zhang Changrang of Caijiapo, Weishan County, Baoji City, Shaanxi Province, called the newspaper and said that the symptoms of Ye Huanggen black appeared on the onion grown in his hometown. He did not know what caused it. In this connection, the reporter interviewed Zhang Shuxue, a professor at the College of Horticulture, Northwest A&F University. According to Zhang Shuxue, if sprigs of sporadic distribution of this disease are planted on plots of land, they can be diagnosed with root rot. Then, what causes the occurrence of root rot of green onions, what specific diseases are there, and what specific prevention and control measures are there? Zhang Shuxue gave detailed answers for growers.
Etiology
Root rot of Welsh onion is similar to root rot and is a fungal disease. It is a disease caused by various pathogens such as Pythium, Fusarium, and Phytophthora. The pathogens overwinter in the soil or on sick and sick bodies, becoming the main primary infestation source for the following year. The pathogens invade the roots or roots of the wound and spread through rain or irrigation water. Therefore, the low-lying terrain, poor drainage, water accumulation in the field, continuous cropping, leakage of dripping water in the shed, and injury to the plant roots are serious. In the nursery areas, soils with large stickiness, easy compaction and poor ventilation, which impede the growth of roots, are also susceptible to disease.
disease
Onion root rot enters the peak of onset in May, and its occurrence is related to climatic conditions. The main damage seedlings, the adult stage can also be disease. At the beginning of the disease, only the individual roots and roots were susceptible, and gradually spread to the main root. After the main root is affected, the early plants do not show symptoms. As the degree of rot in the roots increases, the function of absorbing water and nutrients gradually weakens. The supply of nutrients in the aboveground part is in short supply, the new leaves are yellowed first, and strong light and large evaporation occur around noon. At that time, the upper leaves of the plants showed wilting but they recovered at night. When the condition is serious, the wilting condition cannot be restored at night. The whole plant leaves yellow and withered, the root bark becomes brown, and the whole plant dies.
Control methods
Reasonable crop rotation is a key factor that causes root rot of green onions. Due to continuous cultivation for many years, more pathogenic bacteria are found in the soil, which can easily cause root rot to die from green onions due to infection. Therefore, it is very important to rotate the plots of welsh onions and other crops, but take care not to rotate with garlic or leeks.
Control of Soil Humidity During the process of planting onion, if the soil moisture is too high when the soil is cultivated, it will affect the normal breathing of welsh onion roots, reduce the self resistance of welsh onions and aggravate the occurrence of diseases. Therefore, in the rainy season, we must pay attention to the drainage of large fields, to avoid stagnant water roots and induce root rot of green onions.
The prevention and cure of the root rot of green onions and the prevention of the early stage are very important. Before cultivating the green onions, biological bacterial fertilizer can be applied along with the water to increase the beneficial bacteria in the soil and inhibit the spread of pathogenic bacteria.
Spraying pharmaceuticals because the root rot is a bacterial disease, contagious. Therefore, spraying pesticides on the land where the root rot has occurred is a key to preventing uninfected areas. Zhang Shuxue suggested to farmers that thiophanate-methyl sulfate and streptomycin sulfate may be used as the spray agent.
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