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~ s <br />grass cover than the control plus streambank wheatgrass or thickspike wheatgrass and <br />I4% more cover than the control plus Russian wildrye. <br />Results from the Colorado and Wyoming sites indicate that Russian knapweed was <br />controlled best by Curtail. However, the treatment by seeded grass interactions that were <br />detected at the Wyoming site were most revealing. Few differences were apparent within <br />the treatment by seeded grass interaction effect on Russian knapweed biomass; but, upon <br />examining the interaction effect on Russian knapweed control, the Curtail combined with <br />any seeded grass species generally controlled more Russian knapweed than other <br />suppression treatments combined with grass seeding (with one notable exception <br />mentioned above). Relative to grass establishment and recovery of the infested site, <br />crested wheatgrass established the best but successful establishment occurred only when <br />crested wheatgrass seeding was preceded by a herbicide application, as evidenced by the <br />treatment by seeded grass interaction effect on seeded grass biomass and especially seeded <br />grass cover. Our data suggest that to achieve acceptable Russian knapweed control and <br />revegetate the site to desirable grasses, Curtail combined with crested wheatgrass seeding <br />may provide the best opportunity to be successful. However, ultimately the goal of site <br />recovery is to revegetate the area with desirable grasses and produce harvestable forage <br />for domestic livestock and wildlife and the Escort plus crested w°heatgrass seeding <br />management system represents the best opportunity for success as evidenced by the <br />interaction effect on seeded grass biomass; but, this management system will have to <br />augmented with additional herbicide treatments after grass establishment to reduce the <br />Russian knapweed population to acceptable levels. Regardless of the choice of <br />suppression treatment, our data strongly indicate that Russian knapweed is controlled <br />better when suppression treatments are combined with perennial grass seeding compared <br />to suppression treatments alone and site recovery is much more effective with the <br />management systems compared to suppression treatments alone. <br />-14- <br />