我国棉区分布很广,已发现的棉苗病害有20余种,北方棉区危害最严重的有立枯病、炭疽病、红腐病等。发病率一般为20%～30%,严重时达50%～90%。尤其在多雨、阴湿、低温或冷暖气候剧烈反复时最易发生,且往往是混合并发,成灾较多。轻的引起僵苗、病苗,重的导致烂芽、烂根,叶枯茎腐, Cotton is widely distributed in our country. More than 20 species of cotton seedlings have been found. Most of the cotton harms in the northern cotton region are blight, anthracnose and red rot disease. The incidence is generally 20% to 30%, severe up to 50% to 90%. Especially in the rainy, damp, cold or warm climate is most likely to occur when repeated, and often mixed and complicated, more disaster. Light caused by stiff seedlings, disease seedlings, heavy cause rotten buds, rotten roots, leaf stem rot,