Spotted Knapweed Biocontrol Effort




Thirty people attended two workshops held in Judith Basin County in August to learn more about biological control of a common weed pest here in central Montana. Spotted knapweed was the focus of the meeting, along with information about Houndstongue, Canada Thistle, and Cheatgrass biocontrol agents. Guest speaker Melissa Maggio-Kassner, the Montana BioControl Coordinator, discussed some of the common misconceptions and myths surrounding biocontrol.

 After classroom presentations in Raynesford and Geyser, we headed to the field and made two releases. The Cyphocleonus achates, a root weevil, was the insect dispersed. Some in the area may remember a previous release of a seed head weevil of the Larinus spp. years ago. In searching the knapweed stands, the Larinus larvae was discovered in many plants. The Larinus makes its home in the seed head of the mature knapweed plant, and then exits in the summer of the following year through a hole in the seed head. The releases made will be repeated next summer in an effort to reduce the cost of weed control for local producers. Biological control efforts are a useful tool in areas that are hard to access with sprayers or animals. Once established, these populations will survive as long as the plant it feeds on is present.

Read more program highlights from MSU Extension in Judith Basin County.