Canada Thistle
Biological Control Agents
This weed is naturalized throughout the county, almost anywhere there is water some Canada thistle can be found. Since the early 1990’s we have been using bio-control agents to try to control the vigor and spread of this tough perennial weed. Four insects have been released on Canada thistle.
The Canada thistle stem weevil, Ceutrohynchus litura, seems to be having the greatest effect on the patches where it has been released. It is a difficult insect to collect and it is more cost effective to purchase this insect to establish new populations.
For more specific information on Ceutrohynchus litura, visit the Bio-control.com website.
The Canada thistle stem gall fly, Urophora cardui, populations have expanded to the point where the stem galls are collected for redistribution in the fall.
For more specific information on Urophora cardui, visit the Bio-control.com website.
A defoliating beetle, Cassida rubiginosa, and the Canada thistle budweevil, Larinus planus, have become established and are having some effect on Canada thistle.
For more specific information visit the National Sustainable Agriculture Information Service website.
For more information on Bio-control of Canada Thistle visit:
Colorado State University Extension Service- Canada Thistle Management
Invasive.org- Biological Control of Canada Thistle
Government of Saskatchewan- Canada Thistle and its Control