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.~-;~ : ~ ~ ~ • ~~o III IIIIIIIIIIIII III <br />~, ~ <br />Umaersin <br />Cooperati~~e Extension <br />Colorado Statc Cnivcrsit) <br />Fort Collins, C<dorado Flli_i <br />January 16, 1988 <br />Mr. Terrel Johnson <br />Yampa Valley Coal Co. <br />29588 RCR (r29 <br />Oak Creek, CO 80467 <br />Dear Mr. Johnson: <br />Jim Stanko, Routt County Extension, asked that I write you <br />and provide information about herbicides that will control <br />several weeds (Canada thistle, poison hemlock, houndstongue, <br />cluster tarweed, catchweed bedstraw, and sagebrush). He also <br />indicated that you desired information in addition to that found <br />in the Pest Control Guide (i.e., 2,4-D and Banvel, and Tordon) <br />such as Telar. <br />Telar is a relatively new herbicide that inhibits an enzyme <br />that catalyzes the biosynthesis of aromatic amino acids in <br />plants. If plants cannot produce these amino acids (valine and <br />isoleucine), protein synthesis is incomplete and plants quit <br />growing and die. Telar will readily control Canada thistle, <br />catchweed bedstraw (stick tights) if applied at 1 oz of product <br />per acre. However, timing for Canada thistle control is <br />critical; applications should be made when Canada thistle is in <br />the bud stage or best control is achieved when applied in fall. <br />Also, we have found that treating Canada thistle in late spring <br />(about mid- to late-June) with 2 lb ai/A of 2,4-D followed by 1 <br />oz of Telar in fall provides excellent control for at least two <br />seasons. Telar control of Canada thistle is very slow; do not <br />look for symptoms similar to 2,4-D or Banvel. Canada thistle <br />treated with Telar will become chlorotic (turn yellow), <br />eventually turr. brown and die. It may take an entire growing <br />season for results to be seen. Telar should be applied to <br />catchweed bedstraw in spring. Telar will not control the other <br />weeds you listed. Telar is a non-crop herbicide and cannot be <br />used on pasture or rangeland. <br />Tordon 22K is very cost effective to use even though it is <br />restricted use and one has to be licensed to apply it. Tordon is <br />registered for use in permanent pastures, rangeland, and non-crop <br />thus, you could use it in more areas than Telar. Tordon 22K <br />(applied at 1 lb ai/A) is equally effective on Canada thistle as <br />Telar and Tordon can be applied anytime Canada thistle is <br />actively growing (from early spring through fall). However, <br />Canada thistle is best controlled with any herbicide when applied <br />in fall (e.g. late August to September depending on weather). <br />Houndstongue and catchweed bedstraw also are readily controlled <br />Colorado Statc University, U.S. Ikpartment of Agriculture and Colorado counties cooperating. <br />Coopera[Ive Extension programs arc available [o all x~ithout discrimination. <br />