Recognition and Prevention of Green Onions
There are two types of green onions: physiological dry tip and pathological dry tip. The latter, "white dry" and "green dry," often make it impossible for the onion farmer to distinguish between them. It is difficult to prescribe the right medicine, leading to miss the best timing for prevention and control. Here, briefly explain the causes of the two symptoms and prevention measures.
White stem is caused by epidemic diseases, and it is prone to occur under high temperature and high humidity conditions. In case of cloudy days, it is also the main cause of the current development of green onions. At the beginning of the disease, the lesions were dark green, water invaded, and the lesions were gray and white after expansion. The rim was not obvious and the leaves were withered. When the disease was severe, the field was white. Polic and metalaxyl manganese zinc can be used as control agents. However, it should be noted that because there is a layer of wax on the surface of the onion leaf, it is necessary to pay attention to the addition of silicone additives during spraying to improve the adhesiveness of the agent.
Qinggan is a gray mold disease. The disease is seriously ill at night when the temperature is low and the humidity is high. Now it has gradually become a secondary disease. At the initial stage of the disease, there were white spots on the leaves, nearly round or oval, with a diameter of 1-3 mm, which developed from the tips of the leaves and gradually became flaky, causing the onion leaves to curl and die. Anti-pharmaceuticals can be used for prophylaxis, quick-acting, nicotinamide, etc. Silicone additives are also added to improve control efficiency.
In addition, seed flies can also cause sharp green onions, seed fly larvae damage into the roots of the onion hazards, pull up the onion can be seen roots turn brown, causing the aboveground tip dry, severe root rot or dead.
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