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' Nelson Mining Resource <br /> Integrated Noxious Weed Management Plan <br /> ' August 2019 <br /> Page 10 <br /> bag and properly dispose of the flower heads. Cut-off flower heads can still develop viable seeds. <br /> ' The remaining plant should be cut off below the soil surface to keep it from blooming again. <br /> Chemical/Herbicides — Herbicide applications to control musk thistle are best done twice per <br /> ' year: once in the spring (late March through May) before plants have bolted and again in the fall <br /> as the plants prepare for winter dormancy(late September or early October)before the first killing <br /> frost. Herbicide applications will be most effective during these plants' rosette stage. Plants that <br /> ' have bolted are not very susceptible to herbicides (this will be a waste of money and time). Also, <br /> if the plant is in bloom when it is sprayed, the seeds can still mature and disperse. An appropriate <br /> surfactant mixed with the herbicide(refer to the label)will aid with the absorption of the herbicide <br /> into the plant and you will achieve better control results. Remember: only spray rosettes that have <br /> not bolted. <br /> ' Biological — Biological controls are available for musk thistle control. The seed head weevil <br /> (Rhinocyllus conicus) and the crown weevil (Trichosirocalus horridus) insects are effective on <br /> ' large infestations. When used together, these insects provide fair to good control. Expect to wait <br /> at least 3 to 5 years for the insects to establish significant populations and achieve optimum <br /> management results. Insects can be obtained at no charge from the Colorado Department of <br /> Agriculture. However, the Department of Agriculture discontinued distribution of the seed head <br /> weevil (Rhinocyllus conicus) this insect since it was released in Colorado in the 1970s is now <br />' found almost everywhere in the state. The musk thistle crown weevil (Trichosirocalus horridus) <br /> is currently established in many areas around the state but is still being distributed. <br />' 3.3 LIST C WEED SPECIES — CONTROL METHODS NOT REQUIRED <br /> 3.3.1 Cheatgrass <br /> 1 Cultural — Establishment of selected, aggressive grasses can be an effective cultural control of <br /> cheatgrass. Good grazing management will stimulate grass growth and keep pastures healthy. <br /> Healthy pastures may be more resistant to cheatgrass invasion. Bare spots caused by overgrazing <br /> are prime habitat for weed infestations. <br />' Mechanical—Fire,mowing,grazing,tillage,and inter-seeding competitive species have all shown <br /> promise in reducing cheatgrass populations. Long lasting control requires a combination of <br />' chemical, physical, vegetative suppression, and proper livestock management. <br /> Chemical/Herbicides Herbicides are available. Pending the chemical selected, applications are <br /> best done twice per year: once in the spring (late March through May) and again in the (late <br /> September or early October). <br /> Biological—Biological control is limited. Rabbits and mice will feed extensively on the seedlings <br /> as will migratory grasshoppers. But there is no long-term bio-control agent available. <br />