黑斑病是西洋参主要病害,东北、华北、华中栽培区普遍发生。通常新区发病轻,栽培年限越长,发病越重。各地气候条件不同,发病时期也不同。一般是在西洋参出苗阶段开始发生,侵染茎、叶、花、果实。6—8月份气温升高,空气湿度增大,如防治不当将会发生大面积蔓延,致使西洋参枯萎,果实干瘪,种子减产。一、症状:发病初期有近圆形或不规则的暗褐色病斑,呈水浸状。后期斑点中部变成黄褐色,外缘明显轮纹,显有锈棕色的宽边。病斑干枯后容易破裂,潮湿天气流行很快,病斑常互相汇合在一起,使叶片枯死。茎、叶柄和花梗感病,初期呈暗绿色长斑,逐渐变为褐色,蔓延迅速。在空气湿度较大的条件下,斑点上生有一层黑色霉状物,重者早期折倒死亡。果实受害时,表面有 Black spot disease is the main disease of American ginseng, northeast, north, central China cultivation area. New area usually light disease, the longer the cultivation period, the more severe the disease. Different climatic conditions all over the period of onset is also different. Generally occurs in the emergence stage of American ginseng, infested stems, leaves, flowers, fruits. June-August temperature increases, the air humidity increases, such as improper prevention will occur a large area spread, resulting in wilted wort, fruit shriveter, seed production. First, the symptoms: early onset of nearly circular or irregular dark brown lesions, was flooded. After the middle of the spot into a brown, the outer edge of the obvious round pattern, rusty brown broadsides. Lesions easily rupture after drying, wet weather epidemic quickly, lesions often meet each other together, so that leaves withered. Stems, petiole and pedicel susceptible, early dark green spot, gradually turned brown, spread rapidly. In the air humidity conditions, the spots have a layer of black mildew, heavy early fold down death. Fruit damage, the surface there