Onion purple spot is an important disease on the onion, which may occur during the whole growth period of onion, and also occurs in other onion vegetables. 1, symptoms. The stalks, which mainly damage the leaves and the seedlings, initially showed water-stained white dots, followed by a pale brownish or spindle-shaped depression, continued to grow brownish or dark purple, surrounded by yellow halos, and the disease minister was dark brown or Black gray with a concentric filamentous arrangement of mildew, the disease is soft and easy to break. The high incidence of pedicels in seed plants causes the seeds to shrink and fail to mature sufficiently. The bulbs can also be jeopardized and rot before harvest. 2, the cause of the disease. The pathogenic bacteria is a semi-known fungus subphylum fungi. By using mycelium in the host or with the diseased body in the wintering of the soil, conidia are produced in the following year, spread by airflow or rainwater, penetrate from the stomata, wound or directly penetrate the epidermis, optimal incidence at 24-27 °C. , less than 12 °C is not disease. The disease is severe when it is warm and humid, cloudy and rainy, or when there is no fertilizer, drought, weak plant growth, or when the onion thrips bite the leaves and cause wounds. 3, control methods. (1) Clean the countryside and implement a crop rotation to avoid replanting the onion vegetables. (2) Strengthen management, apply more base fertilizer, reasonably apply fertilizer, and drain water after rain, so that the plants grow robustly and enhance resistance to disease. (3) Timely control of onion thrips so as to prevent the plants from causing wounds. It can be treated with 50% dimethoate EC 1000 times. (4) Using disease-free seeds, the seeds can also be soaked with 40% formaldehyde 300 times for 3 hours, and washed immediately after the leaching. (5) Spray 75% chlorothalonil WP 500-600 times, or 58% metalaxyl WP WP 500 times, 64% WP 50 times, or 50% CAP Wettable powder 1500 times, every 7-10 days, spray a total of 3-4 times. China Agricultural Network Editor