洋葱是陕南地区仅次于大蒜的又一大经济作物,年种植面积达5500hm2以上。近几年洋葱种植比较集中,霜霉病时常发生,而且许多年份发生程度较重,往往造成洋葱叶片大面积干枯,植株逐渐枯萎死亡,一般地块减产幅度在20%～50%,成为严重影响陕南地区洋葱生产的一大障碍。为此,我 Onions in southern Shaanxi is second only to garlic, another major cash crop, the annual planting area of ​​more than 5500hm2. In recent years, the cultivation of onion is more concentrated, downy mildew often occurs, and in many years the degree of occurrence of heavy, often resulting in large areas of onion leaves dry, plant wilt died, the general mass production cuts in the range of 20% to 50%, a serious impact Onion production in southern Shaanxi a major obstacle. For this, me