MDARD requests comments on weevil control of spotted knapweed (star thistle)
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EmailThe Michigan Department of Agriculture and Rural Development (MDARD) requests comments from beekeepers and other stakeholders by March 6 for input on potential use of insects for control of spotted knapweed (also known as star thistle) in Michigan.
The Michigan Department of Agriculture and Rural Development (MDARD) requests comments from stakeholders on permitting the release of weevils to control spotted knapweed (Centaurea stoebe micranthos), also known as star thistle. The two weevils, seedhead weevil (Larinus minutus) and root boring weevil (Cyphocleonus achates), feed on spotted knapweed.
Beekeepers are considered stakeholders on this issue, and MDARD notes, “Beekeepers rely on it as a crucial late-season nectar source, particularly in areas where other plants have stopped blooming” and “Removal or widespread control of spotted knapweed therefore may have a negative effect on…the beekeeping industry.” Another positive environmental impact of spotted knapweed that MDARD notes is that “Native pollinators have been observed feeding on spotted knapweed.”
MDARD describes negative environmental impacts of spotted knapweed, including displacement of native plants and reduced biodiversity, impacts of grazing resources, degradation of soil and water resources, and hindrance to restoration efforts. Each of these impacts is explained in the call for comments.
The call for comments also describes the regulatory authority, background, management approaches, and the current status of biological control insects in Michigan. MDARD is considering four approaches for permit approval, including blanket approval, conditional approval, research-only use, and no approval.
MDARD sent the call for comments via email. Stakeholders can subscribe to MDARD’s email lists. MDARD also lists the Request for Comments: Potential Use of Insects for Control of Spotted Knapweed in Michigan on its Invasive Species webpage.
MDARD invites comments from community members, stakeholders and experts via an online survey by 11:59 p.m. Eastern on Friday, March 6, 2026.
