Brown onion spotting, also known as tip verticillium wilt, is mainly harmful to the leaves. The infected leaves are easy to start from the upper part. The initial spot is water-soaked yellow-brown spots, followed by fusiform lesions, generally 10-30 mm long and 3-6 wide. In millimeters, the middle part of the spot is gray-brown and brown on the edge. It is easy to produce black dots on the surface of the plaque, that is, the ascospora shell. In severe cases, several lesions merge, resulting in partial dryness of the leaves.
Control methods: (1) Use high-temperature white varieties, tri-leafed Qi, chicken onions, Zhangqiu green onions and other heat-resistant varieties. (2) Strengthen management, timely drainage after rain, prevent over-wetting of green onions, enhance root activity, and enhance resistance to disease. (3) In the early stage of onset, spray 50% speeding wettable powder or acetaminophen wettable powder 1000 times, 50% carbendazim wettable powder 800 times or 70% thiophanate-methyl wettable powder 1000 times. Liquid, plus 75% chlorothalonil wettable powder 800 times, once every 7-10 days, even sprayed 2-3 times.
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