Effective landscape scale management of Cirsium arvense (Canada thistle) utilizing biological control

Abstract

The stem mining weevil, Ceutorhynchus litura Fabricius, the gall forming fly, Urophora cardui L., and the seedhead weevil, Larinus planus Fabricius, were established as biological control agents on an 1800 hectare multiple-habitat wildlife refuge in northwestern Oregon in the mid-1990s. At the time, Canada thistle was the most wide spread, aggressive, and difficult weed to control and was being contained only by an extensive herbicide control program. A ten-year monitoring program for these natural enemies (1997 through 2007) showed a significant decline in Canada thistle (Cirsium arvense (L.) Scop.) plant abundance along with a measurable decrease in individual plant size and flowering. A few small stands of Canada thistle still remain that seem resistant to biological control but the need for direct control using herbicide has been discontinued as it is felt that the few scattered remaining populations are no longer an ecological threat and instead serve an important role in acting as a permanent reservoir for the biocontrol agents.

Citation

Markin, G. P.; Larson, D. 2013. Effective landscape scale management of Cirsium arvense (Canada thistle) utilizing biological control. In: Wu, Yun; Johnson, Tracy; Sing, Sharlene; Raghu, S.; Wheeler, Greg; Pratt, Paul; Warner, Keith; Center, Ted; Goolsby, John; Reardon, Richard, eds. Proceedings of the XIII International Symposium on Biological Control of Weeds; September 11-16, 2011; Waikoloa, Hawaii, USA. Session 9: Post-release Evaluation and Management. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team. Online: http://www.invasive.org/proceedings/pdfs/Markin.pdf