Approximately 150,000 Spotted Knapweed Weevils have been released in the Fisher River corridor, including the Thompson Chain of Lake Fishing Access Site, in Lincoln County. A cooperative effort between the Lincoln County Weed District, Montana Fish, Wildlife and Parks, the US Forest Service, Montana Department of Transportation, Montana Department of Agriculture, Plum Creek Timber Company, Department of Natural Resources and Conservation, the Eureka School District, and Florence High School in Ravalli resulted in receiving a grant totaling $25,690 for the biological control project. All partners also supplied matched funds totaling approximately $70,000. The weevils were purchased from Biological Control of Weeds, of Bozeman.
Two types of weevils were released: Cyphocleonus achates (Spotted Knapweed Root Weevil) and Larinus minutus (Spotted Knapweed seed head weevils). These weevils specialize in consuming specific parts of Spotted Knapweed plants. The root weevils feed on the stems and roots of Spotted Knapweed plants, while the seed head weevils consume Spotted Knapweed seeds while they are still on the plant.
Biological control methods, like these weevils, assist in controlling and lowering the infestation of specific noxious weeds. Once the selected species of plant dies out and the weevils can find no other patches of the selected species, the weevils die out as well. Biological control methods will not completely control noxious weeds on their own; it often takes a combination of control methods, including the use of herbicide.
For more information, please contact Amy Grout at 755-2706 ext 3; EMAIL: [email protected] or Dan Williams of the Lincoln County Weed District at 293-7781.