杨苗黑斑病,是北方地区杨苗的大害,在内蒙古地区普遍发生。本病的发生与杨树这一属中不同的种和品种有关。小叶杨、小青杨、辽杨极易感病,当年生的杨树播种苗感病最重,损失也最大。开始,从幼苗叶片上出现几个病斑,几天之内病斑就连成片,叶子变黑,干枯、脱落。由于发病急、蔓延快,常因防治不及时,使苗木全部枯死。病害发生在叶片上,也为害叶柄和嫩枝梢。下部叶片先感病,然后向上蔓延。发病初期,多在叶背面产生 Young seedling black spot disease, is the great harm of Yang Miao in the north, occurred in Inner Mongolia. The occurrence of this disease is related to the different species and varieties of poplar. Populus, Populus, Liaoyang very susceptible, then poplar planting seedlings most susceptible, the loss is also the largest. Beginning, there are several lesions from the seedling leaves, lesions within days even into a film, the leaves black, dry, fall off. Due to acute onset, spread quickly, often because of prevention and treatment is not timely, so that seedlings all died. Diseases occur on the leaves, but also damage petioles and shoots. The lower leaves become susceptible and spread upward. Early onset, mostly in the back of the leaves produce