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Tordon applied at flowering for three consecutive years decreased shoot density to zero. However, the same treatment applied for three years at two other locations (White River drainage, elevation approximately 8,500 feet) controlled 69 percent and 35 percent of yellow toadflax. Telar also may be used to control yellow toadflax in non-crop azeas. In an experiment conducted in Middle Pazk near Parshall, Telar at 1.25 ounce/A applied during flowering or in fall convolled 84 percent of yellow toadflax one year later. Several classical biocontrol agents are Escort, 2,4-D amine, Banvel, and Paramount controlled from 5 percent to available to use against toadflaxes. 24 percent of yellow toadflax one year after single treatments were applied at However, the success of these agents flowering. Plateau showed some potential to control yellow toadflax in another remains largely unknown. Colorado experiment where 8 fluid ounces per acre applied once in fall controlled 59 percent of yellow toadflax one year later. While this level of control is unsatisfactory, sequential treatments may increase control but experiments must be conducted to test this hypothesis. Mechanical and Chemical Control of Yellow Toadflax Mowing combined with spraying Tordon did not improve control in an experiment conducted near Hesperus, Colorado. Yellow toadflax was mowed three times per yeaz then treated with Tordon at 4 pt/A in fall for two consecutive years and compared to Tordon applied at 4 pdA a[ flowering also for two consecutive yeazs. Yellow toadflax control was the same (85 percent) whether Tordon treatments were combined with mowing or not. Biological Control of Toadflaxes Several classical biocontrol agents are available [o use against toadflaxes. However, the success of these agents remains largely unknown. A defoliating moth (Calophasia lunula), an ovary-feeding beetle (Brachyptemlus pulicarius), and two-seed capsule-feeding weevils (Gymnaetron antirrhini and G.netum) have been released in the U.S. and Canada to control all toadflax species. Particularly the flowering and seed feeding insects should help decrease seed production. A stem-boring weevil (Mecinus janthinus) and aroot-boring moth (6teobalea intermediella) also were released in Canada and the U.S. to control all species of toadflax. These species may help to control shoots and seed production as well as decrease root vigor, but data aze unavailable [o document their effects. Several of these classical biocontrol agents aze available from the Colorado Department of Agriculture Insectary in Palisade. Very few published studies aze available to determine whether grazing by livestock will effect any control of Dalmatian or yellow toadflax. ' 1C G. Beck, Colorado State University Issued in furtherance of Coopertive Extension work, Acts of May 8 and June 30, 7914, in Cooperative Extension weed science cooperation with the U.S. Department of Agriculture, Milan A. Rewerts, Director of Cooperative specialistandprokssarofweedscrence, Extension, Colorado State University, Fort Collins,Colorado. Cooperative Exension programs are bioagriculturalsciences andpest managment. available to all without discrimination. No endorsement of products is intended nor is criticism implied of products not mentioned.