Spotted Knapweed Biological Control Assessment A two-year study on the establishment and impact of biological control agents on the invasive spotted knapweed within the Clearwater Basin of north central Idaho.
In the Clearwater Drainage Basin of north central Idaho, spotted knapweed is one of the most problematic and prevalent weeds infesting public land. Biological control has long been one of the most common methods to manage spotted knapweed on public land in this region. In 2011 and 2012, MIA Consulting, in conjunction with the US Forest Service and Idaho County Weed Control, conducted a large-scale study to determine the efficacy and site preferences for biological control agents on spotted knapweed populations within the Clearwater Basin. We collected transect and random sample monitoring data for 70+ sites for two consecutive field seasons. Data were analyzed to determine the efficacy and establishment trends of multiple biological control species. A comprehensive literature review was conducted, and all results from this study were placed in the context of this weed biocontrol system continent-wide. Results and recommendations were compiled into easy-to-understand annual reports shared with all stakeholders in the study area.