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LIST B <br /> Russian knapweed - Acroptilon repens <br /> A deep-rooted, creeping perennial that reproduces mainly from adventi- <br /> tious buds on the roots, but it also reproduces from seed. It is allelo- <br /> pathic, meaning it exudes a toxic substance that inhibits the growth of sur- <br /> rounding plants. It is also toxic to horses, and prolonged consumption re- <br /> sults in "chewing disease." <br /> Identification: <br /> • Flowers: Pink to purple, urn-shaped, and solitary at the ends of <br /> upper branches, pointed papery tips on rounded bracts. <br /> • Stems: Upright, branched, covered in short stiff hairs. <br /> • Roots: Horizontal, vigorous, and black with a scaly appearance. <br /> Control methods: <br /> Biological: <br /> The gall midge, Jaapiella ivannikovi, is currently being established <br /> by the Colorado Department of Agriculture, but is not yet available <br /> to the public. <br /> Mechanical: <br /> Mow several times before plants bolt. Most effective when mowing <br /> is combined with fall herbicide treatment. <br /> Chemical: <br /> Chlorsulfuron: Apply in spring from pre-bloom to bloom, <br /> and in fall to the rosettes. <br /> Aminopyralid: Apply in spring and summer to plants in the bud and <br /> flowering stage, or apply to dormant plants in the fall. <br /> *Picloram: Apply in spring to the bud/early flower stage, <br /> and in the fall to rosettes or to dormant plants. <br /> '`Restricted-use chemical <br /> 42 <br />