Fighting to Win the War on Weeds

In spring 2006, TRLT received a grant for a landscape-scale weed control initiative to help private landowner efforts to control Canada thistle along the Teton River corridor and adjacent lands in Teton Valley. Canada thistle, a noxious weed in Idaho, is a highly competitive perennial weed that occurs in a large range of habitats including cropland, riparian areas and pastures. This weed is particularly hard to control because of its deep, creeping root system. Canada thistle threatens productivity of cropland, rangeland and pasture, and it can replace native vegetation, which negatively impacts wildlife habitat.

The project takes an integrated approach to controlling Canada thistle along the river corridor by using biological control insects and herbicide. The Land Trust released colonies of a stem gall fly in the Woods Creek Fen area. These insects, which are specific to attacking Canada thistle, can weaken or stop reproduction of Canada thistle. Unlike using herbicides, impacts of biocontrol insects on thistle populations may not be noticeable for three to five years.

In addition to biocontrol releases, TRLT has distributed over 40 quarts of the herbicide Milestone to 15 private landowners in Teton Valley. A relatively new herbicide, Milestone has been found to be very effective in controlling Canada thistle. TRLT hopes to secure similar funds in the coming years to continue this program.

TRLT applied for the Idaho State Department of Agriculture grant through the Upper Snake River Cooperative Weed Management Area (CWMA). The Upper Snake River CWMA was established to coordinate area-wide activities to prevent, contain and control non-native invasive plants and noxious weeds on public and private lands within Bonneville, Teton, Madison, Jefferson and Bingham counties. TRLT has been a member of the CWMA Steering Committee since 2006. ■