1, soft rot; Soft rot of scallion is a bacterial disease, which is easy to occur in high temperature and high humidity environment. Usually, we should pay attention to the humidity in the field to avoid excessive water accumulation and root rot. Moreover, it can avoid damage to plants when cultivating, and it can be prevented and controlled by spraying streptomycin sulfate in agriculture when the disease occurs.

2. Purple spot disease: The purple spot disease of scallion mainly harms leaves and pedicels. When the disease occurs, white spots like water stains appear at the lesion, and then gradually become light brown round or spindle-shaped, which is more serious in summer. When planting scallion, it is necessary to reasonably rotate crops, increase the application of organic fertilizer and phosphorus and potassium fertilizer, and improve the disease resistance of plants.

3. Onion rust: Onion rust mainly harms the stems, leaves and pedicels of Chinese onion. At the time of onset, the lesion presents orange-yellow or dark-brown sores, and at the later stage, rusty powder is emitted from the lesion. Usually, phosphorus and potassium fertilizers should be added, and chemicals such as mancozeb and chlorothalonil should be sprayed at the early stage of onset, once every 10 day and continuously for 2-3 times.

4. Submerged flies: Submerged flies are mainly harmed by larvae. They will eat the leaves of green onions and eat the mesophyll tissues constantly, which will lead to the decline of their yield and quality. Therefore, after harvesting, green onions should be thoroughly cleaned up, the sick plants should be taken out of the field, and then the middle eggs wintering underground should be thoroughly dug up, or sprayed with abamectin.