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5.0 RECOMMENDED CONTROL PLAN <br />Canada thistle and Russian knapweed are both noxious weeds due to their resistance to stan- <br />dard control methods and their tendency to reproduce from the roots, producing dense mono- <br />cultures that out-compete native plants. They are stress-tolerant and can grow in a wide variety <br />of conditions including poor soils and low rainfall. Our recommendations for the control of the <br />30X60-foot patch of Russian knapweed and the 20X50-foot patch of Canada thistle are based <br />on the patches' sizes, which are relatively small, and the fact that land managers at Mesita Hill <br />have limited time in which to execute an effective weed control program and to follow up on its <br />success. <br />The most effective and complete method of control for these two small patches is a complete <br />removal of the plants with their surrounding soil. Since Canada thistle roots may penetrate soil <br />to depths more than 15 feet and extend laterally up to 15 feet every year, at least this amount of <br />surrounding soil must be removed with the plants for effective eradication. This plant and soil <br />material should be buried on site and covered with at least 5 feet of soil. Care should be taken <br />that all excavated material is fully buried or this method may serve to spread, rather than con- <br />trol, the weed infestations since new plants can establish from roots as small as % X '/8" as long <br />as 100 days after disturbance. Also, this method should not be performed in the fall when the <br />seed heads are ripe and easily dispersed. <br />If complete removal of the plants and their soil is not possible, the key to controlling infestations <br />of this weed is to stress the plants with a variety of persistent control methods. Eradication of all <br />plants may not be possible and control may take several years, with regular monitoring and <br />quick responses to the weeds' presence being a critical part of the control plan. In this case, <br />our recommendations for the control of the limited patches of Russian knapweed and Canada <br />thistle are to utilize a dual effort of chemical and cultural controls, i.e., spray the patches with an <br />herbicide and plant competitive desirable species afterward. Several applications of herbicide <br />may be needed and continued monitoring of the patches is essential. <br />The ideal herbicide to apply to either patch depends on the timing of application. Many herbi- <br />cides are considered most effective if applied in the fall, whereas others have equal effective- <br />ness when applied earlier in the growing season. If resources are available for application well <br />before the 2006 growing season, i.e., no later than late February, then those herbicides appro- <br />12