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Noxious Weed and Pest Management
Weed Identification 

  • Mesa County assists in educating local landowners on control of List A and List B for eradication noxious weeds.  “List B for eradication weeds” are weeds that are not very abundant in our county, so they still can be eradicated.  However, these same weeds may be abundant in other parts of Colorado.

    Colorado Noxious Weeds

    Noxious weeds are plants that are not native to North America.  They do not have native insects or diseases to keep them in control and from becoming invasive.  Due to the aggressive competitive nature of these plants they tend to out-compete our native vegetation by forming mono-cultures. 

    “Noxious” is a legal term, not to be confused with “obnoxious”!  Noxious weeds are legally designated by law by a state, according to their abundance and ability to spread as requiring eradication (List A); control or suppression (List B) and a plan; or education, research, and biological control (List C).

    Approximately 50% of noxious weeds occur in ornamental areas, where non-native plants escape from flower beds, while the remaining 50% occur in agricultural areas, and may escape to roadsides, rangeland, or be transported to flower beds, etc.

  •  List A Species

    List A species in Colorado are designated for eradication, as they are not common state wide, but have the potential to become very invasive and quickly spread and take over an area.  Eradication may be feasible, and the goal is to detect them early, before they become abundant and well established.  Not all of the species on List A are known to exist in Colorado at this time, but the threat from neighboring states in the Rocky Mountain Region is imminent.  The law (Colorado Noxious Weed Act) mandates compliance from local governing bodies (counties and cities), as well as affected public and private landowners.

     List B Species

    List B weed species are species for which state noxious weed management plans have been designed to stop the continued spread of these species. List B weeds are targeted for control or suppression.  List B weeds for eradication, which may only exist in small concentrations in some counties in the state, still have hope of being eliminated, before they become well established.

     List C Species

    List C weed species are species for which state noxious weed management plans have been developed. The goal of such plans will not be to stop the continued spread of these species, but to provide additional education, research, and biological control resources to manage List C species.

     Watch List Species

    Watch List weed species that have been determined to pose a potential threat to the agricultural productivity and environmental values of the lands of the state. The Watch List is intended to serve advisory and educational purposes only. Its purpose is to encourage the identification and reporting of these species to the Commissioner in order to facilitate the collection of information to assist the Commissioner in determining which species should be designated as noxious weeds.

    Colorado Department of Agriculture Watch List PDF Icon

  • Additional Information

    • Colorado Department of Agriculture website
      Has free information on Noxious Weed Fact Sheets; map of where specific noxious weeds occur in the state; contact information for each county weed management specialist; weed free forage and hay sources; paid preparatory materials for testing for Private and Commercial Pesticide Applicators Licenses, locations, times, etc.

    • Gardening and Horticulture: Western Colorado  

    • Master Gardner Help Desk call (970) 244-1836 or visit website

      For free help with weed identification, please bring your complete weed sample, with flowers, leaves, roots and stem, if possible, sealed in a plastic ziploc bag, to the Master Garden Help Desk at the Colorado State University Tri-River Area Extension building west of the Mesa County Fairgrounds at 2775 Hwy 50 on Orchard Mesa, open from 8 a.m. to 5 p.m. Monday through Friday. Or you may call them at: (970) 244-1836. If your weed is identified to be a List A or rare List B (for eradication) noxious weed, a Master Gardener will contact the Mesa County Weed & Pest Coordinator to assist you in identifying the best method for control. County assistance may be available for some of these weeds.


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