2006-12-28_PERMIT FILE - M2006085

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Page 4 of 23 Appendix 1 stores. Therefore, returning infested land to a productive state occurs only overtime. Success requires a sound management plan implemented over several years. CWtural control of Canada Thistle Grasses and alfalfa can compete effectively with Canada thistle if their growth is favored by good management. Maintain fertility and, if possible, moisture at optimum levels to favor grass or alfalfa growth. Soil analysis can easily determine fertility needs. Be cautious with nitrogen fertilizers, because excess available soil nitrogen may favor weed growth. These are essential management steps to ensure optimum desirable plant growth and competition. However, competition alone seldom is effective against Canada thistle. Chemical Control of Canada Thistle Read the label, follow directions and use precautions. Research at Colorado State University shows that Tordon 22K (picloram), Curtail (clopyralid plus 2,4D), Transline (clopyralid), BanveWanquish/Clarity (dicamba), 2,4-D and Telar (chlorsulfuron) are effective against Canada thistle. These hedricides are most effective when combined with cultural and/or mechanical control. BanveWanquish/Clarity, and 2,4-D may be used on pastures, rangeland and non-crop areas. Tordon, Curtail, Telar and Transline may be applied on nonaop areas only. Colorado State University data indicates that BanveWanquish/Clarity or Telaz aze effective when combined with 2,4-D as asplit-season application. Apply 2,4-D, 2 quarts per acre (A), in spring when Canada thistle is ]0 to 15 inches tall, in pre-bud to early bud growth stages. Re-treat in fall with BanvelNanquish/Clarity (2 quarts/A) or Telar (1 ounce/A) to re- growth. Use a surfactant (0.25 percent to 0.5 percent v/v) with Telaz for adequate control. BanvelNanquish/Clarity also may be applied in eazly spring at 2 quarts/A when Canada thistle is in the rosette stage. Tordon (1 quart/A) or Tordon plus 2,4D (1 quart + 1 quart/A) is effective whenever Canada thistle is actively growing. Fall applications are especially effective. Curtail and Transline are effective when applied in spring after all Canada thistle plants have emerged. Apply Curtail (2 to 3 quarts/A) when the oldest Canada thistle plants are entering the bud growth stage and the youngest are in the rosette to bolting growth stages. Apply Transline (2/3 to 1 pt/A) when Canada thistle is in the rosette to bud growth stages. Transline at 1 pUA also is effective when applied in fall. Recent research at Colorado State University shows that the performance of Curtail to control Canada thistle can be improved when preceded by two or three mowings. When Canada thistle infestations occur in situations where root growth would be restricted, such as habitats with high water tables, begin mowing when it is 12 to 15 inches tall. Repeat mowings at about one month intervals. Apply Curtail at 2 to 3 quarts/A in October or about one month after the third mowing. Follow this regimen for two consecutive years. Mechanical control of Canada Thistle Mowing hay meadows can be an effective tool if combined with herbicide treatments. Mowing alone is not effective unless conducted at one-month intervals over several growing seasons. Always combine mowing with cultural and chemical control Mowing at hay cutting stimulates new Canada thistle shoots to develop from its root system. In irrigated grass hay meadows, fall herbicide treatments that follow mowing can be an effective management system because more Canada thistle foliage is present after cutting to intercept herbicide. Additionally, root nutrient stores decrease after mowing because the plant draws on them to develop new shoots.