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Colorado Mate University <br />Extension <br />Range, Pasture and Natural <br />Area Weed Management <br />Fact Sheet No. 3.105 <br />by K.G. Beck* <br />Weeds are spreading rapidly on Colorado <br />rangeland and in pastures and natural <br />areas. Manage weeds during the current <br />growing season to decrease or prevent future <br />infestations. All too often, weed control <br />during a growing season is evaluated in terms <br />of financial return only for that season and <br />not for future impact. <br />All weed management must be applied <br />and evaluated over an extended time to be <br />successful. This is particularly important <br />with rangeland, pasture, or natural area weed <br />management programs. A good manager <br />develops a comprehensive weed management <br />plan and incorporates that plan into a long- <br />term land management program; i.e., weeds <br />are managed to achieve overall land use goals <br />and objectives. <br />Be persistent in weed management, <br />particularly with perennial weeds. Most <br />successful weed management systems require <br />input for several growing seasons. Weed <br />infestations occur over time and seldom can <br />be cured in a single growing season. Soil seed <br />dormancy of most weeds and the extensive <br />root systems of creeping perennials requires <br />that weed management systems in rangeland, <br />pasture and natural areas need to be designed <br />for input over extended time periods. <br />Mapping <br />A comprehensive weed management pian <br />has several key features. First, develop an <br />accurate map of weed infestations. Include <br />information about infestation locations and <br />weed species within those locations. Also, <br />indicate the type of infestation; <br />• scattered infestations less than 10 yards in <br />diameter with just a few plants; <br />• light infestations made up of small patches <br />up to 0.5 to 1 acre in size; <br />'Colorado State !University Extension weed se, ence <br />specialist andprolessor, bioagricuhural sciences and <br />pest management. 11;2013 <br />Naturae Resources Seri-�s 1 Range <br />• moderate infestations from I to 10 <br />acres; or <br />• large dense infestations greater than <br />10 acres. <br />Additionally, include the productive value <br />of land where infestations are located to help <br />determine how much money to spend on <br />weed management during any year and over <br />time. Also, determine habitat, e.g. rangeland, <br />irrigated pasture, around ponds or along <br />streams and rivers, and associated desirable <br />plant species, as these will help you choose <br />appropriate control tools. <br />Integrate Control Methods <br />A key aspect to weed management <br />is to integrate control methods into a <br />management system, <br />• Cultural controls are methods that favor <br />desirable plant growth, such as proper <br />grazing management, irrigation, and <br />seeding vigorously growing, competitive, <br />desirable plant species. <br />• Mechanical control physically disrupts <br />weed growth and includes such methods <br />as tillage, mowing, mulching, burning, <br />and flooding. <br />• Chemical control is the use of herbicides. <br />• Biological control is the use of an <br />organism to disrupt weed growth. <br />Classical biological control uses natural <br />enemies of weeds, such as insects or <br />disease organisms. Biological control also <br />may include use of sheep, cattle, goats, or <br />other large herbivores to control weeds. <br />A good weed -management plan <br />integrates two or more control measures <br />into a management system. For example, if a <br />pasture is infested with leafy spurge: <br />1. Biological control: Use sheep or goats to <br />graze the weed during the growing season <br />to relieve desirable plants from intense <br />weed competition, <br />2. Cultural control: Irrigate, where <br />applicable, to further stimulate <br />desirable plant growth to provide better <br />Quick Facts <br />• Weeds are managed to <br />achieve overall land use goals <br />and objectives. <br />• All weed management must <br />be applied and evaluated <br />over an extended time to <br />be successful. <br />• Mapping weed infestations <br />is the first step in pasture, <br />rangeland, and natural area <br />weed management. <br />• Integrate two or more control <br />methods into a system <br />of management. <br />• Control small, scattered or <br />perimeter infestations before <br />large, dense ones. <br />• Keep accurate records of <br />control procedures and <br />evaluate for success or failure. <br />© Colorado State University <br />Extension. 7197. Revised 1'1113. <br />www.ext.colostate.edu <br />91i <br />WOO <br />