大葱田病虫草害防治大葱的常见病害有紫斑病、霜霉病、锈病、菌核病、黄矮病等；虫害有葱蛆、葱蓟马、潜叶蝇等；杂草有藜、蓼、苋及禾本科杂草等。现将防治方法介绍如下。紫斑病、霜霉病：发病初期喷７５％百菌清可湿性粉剂６００倍液，或７０％代森锰锌可湿性粉剂５００... Common diseases of scallion and pest control on green onions are purple spot disease, downy mildew, rust disease, sclerotinia, yellow dwarf disease and so on; pests include onion maggot, onion thrips, leaf miner, etc. Weeds are quinoa, Amaranth and grass weeds and so on. Now the prevention methods are described below. Purple spot, downy mildew: Early onset spray 75% Chlorothalonil WP 600 times, or 70% Mancozeb WP 500 ...