莴苣叶枯病1919年始发于日本国,后传入我国台湾省,逐渐蔓延至我国国内各主要蔬菜生产区。随着人们食物结构的不断改善,莴苣市场需求量猛增,种植面积迅速扩大,近年莴苣叶枯病成为莴苣生产和加工的一大危害。莴苣叶枯病侵染过程为每年初春,当莴苣幼苗嫩叶刚刚形成时其病菌潜入,先在叶片上出现灰褐色、直径1～5μm不规则多角形斑点,各斑点扩大后跨越叶脉使许多小斑点相融合而成大斑块,最后病斑变成暗 Lettuce leaf blight originated in Japan in 1919, then spread to Taiwan Province of our country, and gradually spread to all major vegetable production areas in China. With the continuous improvement of people’s food structure, lettuce market demand soared, planted area has expanded rapidly in recent years, lettuce leaf blight as lettuce production and processing a major hazard. The infection process of lettuce leaf blight was early spring every year. When the young leaves of lettuce seedlings just formed, their pathogenic bacteria infiltrated. First appeared brownish brown on the leaves and 1 ~ 5μm in diameter irregular polygonal spots. Blending spots into large patches, the last lesion becomes dark