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Annual weedy species may be readily controlled with mowing or physical removal. Perennial species <br />such as thistle (Cirsium) have extensive root systems with significant carbohydrate reserves. For such <br />weed species mechanical methods may only control seed production without seriously affecting the <br />plants survival. Disking or tilling areas containing Cirsium or other noxious species may even <br />increase the azea of infestation due to toot sprouting. In most cases mechanical control methods used <br />alone are not effective against hardy perennial weed species. <br />2.3.3 Biological Control <br />Biological control of noxious and pest weeds can be an effective tool to physically disrupt plant <br />growth and seed development. Edna Mine may use a combination of biological methods including <br />introduction of insect weed predators and species specific plant diseases. Biological weed control <br />methods and practices will be applied at the appropriate time to maximize their effectiveness in <br />preventing seed production. It must be noted that the use of biological controls normally does not <br />eradicate an infestation of weeds; rather they aze capable of reducing weed species vigor and <br />reproduction. The Colorado Department of Agriculture's Biological Weed Control Program has on- <br />going biological control programs for a variety of noxious or pest weed species. A list of weed <br />predator species and weed species controlled by these insects is available on the intemet at: <br />http://www. ag. state.co.us/CSD/insectary/ Weed%20Programs, html. <br />2.3.4 Chemical Control <br />Chemical control of noxious and pest weeds can be an effective tool to disrupt plant growth and seed <br />development. Chemical weed control methods and practices must be applied at the appropriate time <br />to maximize their effectiveness in preventing seed production or for disrupting plant establishment <br />and growth. To avoid development of weed resistance to a particular herbicide through repeated use <br />over prolonged periods of time, a combination of chemical methods will be utilized. These methods <br />include the use of herbicides and plant growth regulators with different modes of action in rotation, <br />tank mix or in sequential applications. Also, herbicides must be applied at the manufacturer's <br />recommended treatment concentration to prevent development of plant resistance. <br />The entry of herbicides into surface waters will be prevented, with adequate buffer strips being used <br />when application occurs in proximity to water bodies. If herbicide use becomes necessary within <br />riparian corridors, hand application on specific targets will be employed with products approved for <br />riparian or aquatic appiication. <br />P&M Edna Mine S - OZ/74/06 <br />