一、霜霉病1.危害症状幼苗和成株均可发病,主要危害叶片、茎、卷须,花梗也能受害。幼苗发病,子叶正面出现不匀的黄化褪绿斑,然后变成不规则枯萎斑。空气潮湿时,病斑背面产生紫灰色霉层。成株期发病多从下部叶片开始,初期在叶片上出现绿色小斑点,并逐渐变为黄 First, downy mildew 1. Harm symptoms Seedlings and adults can be disease, the main hazards leaves, stems, tendrils, pedicels can also suffer. Emergence of seedlings, cotyledons frontal uneven yellow chlorotic spots, and then become irregular withered spots. When the air is wet, purple gray mildew occurs on the back of the lesion. More incidence of adult plant from the lower part of the leaves, the initial emergence of small green spots on the leaves, and gradually turned yellow