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Kusstan Knapweed <br />Page 3 of 3 <br />a single weed management technique. When integrating chemical and cultural control, <br />avoid using herbicide rates that injure grasses because effective competition will be <br />reduced. <br />Russian knapweed is controlled with Tordon 22K (picloram) at 1 to 2 quarts/A. Tordon <br />may be broadcast sprayed up to 1 quart/A or spot sprayed at rates up to 2 quarts/A. <br />Tordon plus 2,4-D (1 to 1.5 pints + 1 quart/A) also will control Russian knapweed. If low <br />rates of Tordon or Tordon plus 2,4-Dare used, application for two consecutive years may <br />be necessary to achieve adequate rnntroi. Apply Tordon any time the weed is actively <br />growing. <br />For Telar (chlorsulfuron), a noncrop herbicide that controls Russian knapweed, <br />application timing is critical. Apply (1 ounce/A) when Russian knapweed is in the bloom <br />to postbloom stage. Earlier applications do not control the weed effectively. Fall is a good <br />time to apply Telar, but it may injure smooth brome or other brome species. Always add <br />a good agricultural surfactant at 0.25 to 0.5 percent v/v to the spray solution. Escort <br />(metsulfuron) is labeled for pasture and rahgeland use. Apply it at 0,75 to 1 ounce/A <br />with a good agricultural surtactant. Optimum timing for Escort is similar to Telar. <br />Cultural corrtrol. Russian knapweed tends to farm monocultures and usually eliminates <br />other plants. Therefore, sowing desirable plant species is necessary after the weed is <br />controlled, Smooth brome will compete with Russian knapweed. Research shows that <br />streambank wheatgrass, thickspike wheatgrass, crested wheatgrass and Russian wildrye <br />established after Russian knapweed was suppressed with herbicides. Sod-forming <br />perennial grasses, like streambank or thickspike wheatgrasses, help prevent reinvasion <br />better than bunch grasses like crested wheatgrass. <br />If the Russian knapweed stand is not too old and grasses are still present, stimulating <br />grass growth by irrigation (where possible) should increase grass competition with <br />knapweed and keep the weed under continual stress. <br />t Colorado State University Cooperative Extension weed specialist and professor, bioagricultural sciences and <br />pest management. 9/98. Revised 3/03. <br />Go to to_p of thisgage, <br />Updated Monday, August 23, 2004. <br />AnswerLink I CSU AaNews I Emolovment I Other Links I Publications I Staff Resources I Site Search <br />CE Home I CSU Home I RamPOint I About Us I Calendar I Staff Directory I Webmaster <br />Disclaimer I Equal Ooportunitv INon-Discrimination Statement <br />http://www. ext.colostate.edu/pubs/natres/03111.html <br />6/20/2005 <br />