二年生白花草木樨第二年返青阶段缺苗断垅十分普遍,往往造成大面积毁种改种。据在右玉杀虎口等4个公社12个大队调查,发病植株一般达38.5-76.8％,缺苗50％以上。一、死亡的主要类型及原因 (一)生理死亡型 1.无芽死亡。由于草木樨生理性退化和品种的变异,冬前不能形成越冬芽。越冬后 Second year white flowers and grass clogs rejuvenation stage of the second year of lack of seedlings is very common, often resulting in large-scale deforestation. According to the investigation of 12 brigades of 4 communes in the right jade killing tiger mouth, the incidence of plants is generally 38.5-76.8%, and the lack of seedlings is over 50%. First, the main types of death and causes (A) of the physiological death 1. No bud death. As a result of physiological degradation of plants and wild varieties of Variety, winter can not form a winter bud. After the winter