论文部分内容阅读
一.棉苗病害的种类及其特征棉病的种类很多,在我国已发生的有30余种,其中常见的约20余种。仅在苗期经常发生且较普遍和严重的有下列7种: (1) 立枯病由半知菌纲Rhizoctonia solani真菌侵害所致。幼根和茎基部先发生凹陷褐色斑块,以后扩大、腐烂,色亦加深;拔出时,患处有菌丝黏附着小土块,风吹摇动;严重受害者,子叶萎垂,幼茎倒伏而死。 (2)猝倒病由藻状菌纲Pythium aphanidermatum真菌为害所致。幼苗根部得病后先呈黄色水肿状,迅即变软、腐烂,色亦转深,但患部不如立枯病的凹黑,促成倒苗极快。
I. The types and characteristics of cotton seedling disease There are many types of cotton disease, which have occurred in our country more than 30 species, of which about 20 common species. The following seven species are common only in seedling stage and are more common and serious: (1) Blight is caused by fungus Rhizoctonia solani. The roots and stem base first depression brown plaques, after the expansion, decay, color is also deepened; pull out, the affected area mycelium adhesion of small clods, the wind shaking; serious victims, cotyledons withering, young stem lodging And die. (2) Damp down disease caused by the phytoplankton Pythium aphanidermatum fungi damage caused. Seedling roots get yellow edema after the first sick, quickly become soft, decay, color also turn dark, but the affected area is not as black as damping off blight, causing the inverted moult extremely fast.