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Page 10 of 23 <br />Russian knapweed <br />Appendix 1 <br />Management <br />• Like other creeping perennials, the key to Russian knapweed control is to stress the weed and cause it to <br />expend nutrient stores in its root system. An integrated management plan should be developed that places <br />continual stress on the weed. Currently, the best management plan includes cultural control combined with <br />mechanical and/or chemical control techniques. A single control strategy, such as mowing or a herbicide, <br />usually is not sufficient. <br />Russian knapweed typically invades degraded areas, dominating the plant community and desirable plants <br />(e.g. perennial grasses). Seeding competitive, perennial grass species (cultural control) after Russian <br />knapweed has been stressed by other control measures (set-up treatments) is essential. Set-up treatments <br />may include chemical or mechanical methods. <br />Cooperative research between Colorado State University and the University of Wyoming showed that <br />chemical set-up treatments were superior to mowing. Curtail (clopyralid + 2,4-D), Escort (metsulfuron), <br />and Roundup (glyphosate) were used to suppress Russian knapweed. Then perennial grasses were sown in <br />late fall as a dormant seeding. Tillage is necessary to overcome the residual allelopathic effects of Russian <br />knapweed. Curtail (3 quarts per acre) (A) or Escort (1 ounce/A) were applied at the bud-gowth stage. <br />Roundup was applied twice at 1 quarUA, first at the bud-growth stage and again about 8 weeks later. <br />Curtail controlled Russian knapweed best, but Roundup failed to control it. <br />None of the herbicides injured seeded grasses. Grasses established similarly among herbicide suppression <br />treatments, even though Russian knapweed control varied. l-Iowever, where Escort or Roundup was used to <br />suppress Russian lrnapweed, additional herbicide ireatrnents would be necessary to achieve acceptable <br />control , <br />While two mowings, eight weeks apart (first at bud-growth stage}, suppressed Russian knapweed during <br />that year, the weed recovered vigorously the subsequent season. Perennial grasses established in the <br />mowing treatments but much less than in herbicide treatments. Two mowings per year for several years <br />may control Russian knapweed better, but further research is needed to test this hypothesis. Currently, no <br />biological control is available for this weed. <br />