胡麻叶斑病在水稻整个生育期皆可发生,苗期和孕穗至抽穗期最易染病,可危害稻株地上各部位,主要危害叶片。苗期叶片受害,病叶上出现芝麻粒状的暗褐色斑点,斑点密生时可致秧苗枯死。如遇潮湿天气,死苗上会生出黑色绒状霉层,即病菌的分生孢子。成株叶片受害,病斑初为褐色小点,逐渐扩大成椭圆形褐斑,芝麻粒大小,病斑周围一般有黄色晕圈,后期中央呈黄褐色或灰白色。发病重时叶片上病斑密布,常愈合成不规则的大斑,最后叶片干枯。受害严重的稻株,生长受阻,分蘖少,抽穗迟。 Flax leaf spot can occur throughout rice growth period, the seedling stage and booting stage to heading stage are most susceptible to disease, which can endanger the ground parts of rice plant and mainly damage the leaves. Seedling leaves damage, sesame granules appear on the sick leaves of dark brown spots, spots can cause seedlings withered dead. In case of wet weather, dead seedlings will give birth to black velvet mildew layer, the germ conidia. The leaves of adult plantlets were affected. Lesions at the beginning of the lesion were small brown dots gradually enlarged into oval brown spots. The size of sesame seeds generally had a yellow halo around the lesion and a yellowish brown or off-white color in the late stage. Severe disease when the leaf spot on the spot, often more irregular large plaques, and finally leaves dry. Severe damage to rice plants, growth retardation, fewer tillers, heading is late.