Musk Thistle
Biological Control Agents
The bio-control program for this biannual weed has been very successful. Two bio-agents were released in Fremont County in the late 1980’s, a seed head weevil, Rhinocyllus conicus,and a crown weevil, Trichosirocalus horridus.
When these agents were released musk thistle had a substantial impact with over 11,000 acres in the County. The insects have had a tremendous impacted the population of musk thistle, there is now only about 1000 acres of this weed scattered across the county none on which is economically important. All the musk thistle found in Fremont County is infested with both of these insects
For more specific information on Rhinocyllus conicus, or Trichosirocalus horridus visit Cornell University's Bio-control website here and here.
For more information on Bio-control of Musk Thistle visit:
Colorado State University Extention- Musk Thistle
