一、发病症状玉米丝黑穗病属于系统侵染,症状多在后期表现出来。但有些病株苗期也表现症状,病苗节间缩短,株形较矮,茎干基部膨大,下粗上细,叶片簇生,叶色暗绿,粗硬而挺直,有时分蘖增多。有些品种叶片从第5叶开始,出现黄色条斑。本病突出症状,表现在穗部受害。病株全部果穗和潜伏果穗都能生长黑穗。病穗除苞叶外,整穗变成一个大黑粉包,成熟后黑粉散失,残留有丝状物,故名丝黑穗病。雄穗(天花)发病多但不是全部受害,病穗外包白膜长圆形,包膜破裂,黑粉散失后也成残留 First, the incidence of symptoms Corn head smut is a systemic infection, the symptoms manifested in the late. However, some diseased plants also showed symptoms at the seedling stage. The internodes shortened, the plant shape was short, the base of the stem was enlarged, the upper and lower stems were fine, the leaves were clustered, the leaves were dark green, coarse and stiff, and sometimes tiller increased. Some varieties of leaves starting from the fifth leaf, yellow streaks appear. Outstanding symptoms of the disease, manifested in the ear victims. All strains of diseased plants and potential ears can grow black ears. Spike panicle addition to bracts, the entire panicle into a large black powder package, the maturity of the black powder is lost, the residual filamentous, so named head smut. Tassel (smallpox) incidence but not all victims, disease panicle outsourcing white film oblong, rupture of the capsule, after the loss of black powder also become a residue