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.. When integrating chemical and cultural control, avoid using herbicide rates that injure grasses because effective competition will be reduced. ~y other control measures (set-up treatments essential. Set-up treatments may include chemical or mechanical methods. Cooperative research between Colorado State University and the University of Wyoming showed that chemical set-up treatments were superior to mowing. Curtail (clopyralid + 2,4D), Escort (metsulfuron), and Roundup (glyphosate) were used to suppress Russian knapweed. Then perennial grasses were sown in late fall as a dormant seeding. Tillage was done and is necessary to overcome the soil residual allelopathic effects of Russian knapweed. Curtail (3 quarts per acre) (A), or Escort (1 ounce/A) applied at the bud-growth stage. Roundup was applied twice at 1 quatt/A; first at the bud-growth stage and the second about 8 weeks later. Curtail controlled Russian knapweed best. None of the herbicides injured seeded grasses and grasses established similarly among herbicide suppression treatments, even though Russian knapweed control varied. However, where Escort or Roundup was used to suppress Russian knapweed, additional herbicide treatments will be necessary to achieve acceptable control. While two mowings, 8 weeks apart (first at bud-growth stage), suppressed Russian knapweed during that year, the weed recovered vigorously the subsequent season. Perennial grasses established in the mowing treatments but much less than in herbicide treatments. Two mowings per year for several years may control Rtusian knapweed better, but further research is needed to test this hypothesis. Currently, no biological control is available for Russian knapweed. Chemical control. In most circumstances, a herbicide alone will not effectively manage Russian knapweed. However, there may be situations where a land manager believes that the population of desirable plants in a Russian knapweed infestation may be sufficient to compete effectively with the weed if it is stressed with asingle-weed management technique. Russian knapweed is controlled with Tordon 22K (picloram) at 1 to 2 quarts/A). Tordon may be broadcast sprayed up to 1 quart/A but one can spot spray at rates up to 4 quarts/A. Tordon plus 2,4-D (1 to 1.5 pints + 1 quart/A) also will control Russian knapweed. If low rates of Tordon or Tordon plus 2,4-D are used, application for two consecutive years may be necessary to achieve adequate control. Apply Tordon anytime the weed is actively growing. The Tordon label prohibits seeding perennial grasses the same year this herbicide is applied. Telar (Chlorsulfuron) is a non-crop herbicide that controls Russian knapweed, but application timing is critical. Apply (1 ounce/A) when Russian knapweed is in the bloom to post-bloom stage. Earlier applications do not control the weed effectively. Falt is a good time to apply Telar, but it may injure smooth brome or other brome species if they are present. Always add a good agricultural surfactant at 0.25 to 0.5% v/v to the spray solution. Escort (Metsulfuron) is labelled for pasture/rangeland use. Apply it at 0.75 to 1 ounce/A with a goad agricultural surfactant. Optimum timing for Escort application to control Russian knapweed is similar to Telar. Cultural control. Russian knapweed tends to form monocultures and usually eliminates other plants. Therefore, sowing desirable plant species is necessary after the weed is controlled. Smooth brome will compete with Russian knapweed. Our cooperative revegetation research shows that streambank wheatgrass, thickspike wheatgrass, crested wheatgrass, and Russian wildrye established after Russian knapweed was suppressed with herbicides. If the Russian knapweed stand is not too old and grasses are still present, stimulating grass growth by irrigation (where possible) should increase grass competition with knapweed and keep it under continual stress. ' H. George, Beck, Colorado State University Issued in furtherance of Cooperative Extension work, Acts of May B and Lune 30, 1914, in cooperation Cooperative Extension weed specialist and with the U.S. Department of Agriculture, Milan A. Rewerts, Director of Cooperative Extension, associate prolessor, bioagricultural sciences Colorado State University, Fort Collins, Colorado. Cooperative Extension programs are available to all and pest management. without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned. Figure 1: Russian knapweed.