列当俗称毒根草,是寄生在向日葵根部的一种恶性杂草,分布在全疆各个向日葵产区。列当传播蔓延很快,目前被国家列为检疫对象之一。一、危害特点列当是典型根寄生杂草,本身没有根,只有称为吸盘的寄生根,吸附在向日葵根际。整个苗株不含叶绿素,不能进行光合作用制造养料,依靠吸取寄主植物营养和水分生活。向日葵植株被列当寄生后,体内养分和水分被列当夺走,因而生长缓慢,茎秆又矮又 Columns commonly known as poison grass, parasitic in sunflower roots of a vicious weed, located in Xinjiang all sunflower areas. When the spread spread when the column is currently one of the countries listed as quarantine objects. First, the hazard characteristics Column is a typical root parasitic weeds, there is no root, only the parasitic roots called sucker, adsorbed in the rhizosphere of sunflowers. The seedlings do not contain chlorophyll, photosynthesis can not create nourishment, relying on the host plant nutrition and water intake. Sunflower plants are listed as parasitic, the body of nutrients and water was Lieduan away, so slow growth, stalks and short