一、症状的识别及发生规律(一)症状的识别。芋疫病发生于叶片、时柄及球茎后,迅速扩大,形成轮纹式病斑。发生在叶片时,初发时出现黄褐色圆形小斑,扩大后有同心轮纹,其叶背轮纹斑非常明显,斑点外围有呈白色霉状物的分生孢子,病斑常汇合成不规则大斑。破裂穿孔。发生严重时,病叶仅残留主脉,状如破伞,至使光合作用的绿叶面积迅速减少。发生在叶柄时,常出现大小不等暗褐色的长椭圆形病斑,病斑 First, the identification of symptoms and the occurrence of (a) the identification of symptoms. Taro disease occurs in the leaves, handle and corms, the rapid expansion of the formation of wheel-type lesions. Occur in the leaves, when the first occurrence of yellowish brown small spots, expand the concentric ring pattern, the leaf back spot is very obvious, speckled white mildew conidia, spot often exchange synthesis Irregular big spot Rupture perforation. Occurrence of serious disease leaves only the main vein left, like a broken umbrella, so that photosynthesis of the rapid reduction of green leaf area. Occurred in the petiole, often ranging in size ranging from dark brown oval lesions, lesions