Scallions are grown across China — chives in the south, green onions in the north. Key diseases: downy mildew, blight, anthracnose, purple spot, grey mould and soft rot. Key pests: thrips, leafminers, root maggots and beet armyworm. Weeds: monocots such as barnyardgrass and sedges such as purple nutsedge.
Downy mildew first shows yellow-white lesions on leaves and stalks. Blight causes wet rot that extends across half the leaf, making it droop, yellow and wither — severe fields can lose up to two-thirds of the leaf tube. Act early at the first symptoms, rotate active ingredients and manage field drainage.