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Noxious weeds are non-native, invasive, plant species whose control is legally mandated. Per the Colorado Noxious Weed Act 35-5.5 all landowners both public and private must control these species on their land. The cultivation and sale of these plants is also illegal. Noxious weeds degrade native ecosystems, reduce forage for wildlife and pollinators, impact agriculture yields, property values, and in some cases human health.
Integrated management is the best option for controlling noxious weeds. Depending on the biology of the plant, certain control methods will be more effective. The Archuleta County Weed and Pest Supervisor can help you create a management plan that uses: mechanical control, biological control, and/or chemical control.
There are five noxious thistle species in Colorado and four occur in Archuleta County. Chemical control in the spring and fall works great on both species and there are biological control agents available for Canada thistle and musk thistle. Hand-pulling or cutting down the plants works well for biennial species such as Scotch, musk, and bull thistle-which all have simple root systems. Canada thistle has a creeping root system and any disturbance below the surface will encourage new growth from the root system. Repeated mowing can deplete the root reserves of this plant after several growing seasons. Solarization can also kill Canada thistle. Solarization should be done with clear or black plastic that will cover the plant for the entire growing season. Clear plastic works faster than black plastic.
The Weed and Pest Department sells herbicides and biological controls during the growing season. We also carry gas cartridges for prairie dog control and grain bait for grasshopper control. We can help release biological controls, conduct property inspections, and create management plans for landowners. We maintain a private spray list each season and can treat around 100 private properties. Once we have reached our capacity, we will direct you to a private commercial applicator in the area.
Property inspections and management plans are free. The sale of herbicides, biological controls, and treatment of private property have costs associated.