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Grassland, Shrubland and Desert Ecosystems
Contact Information
  • Grassland, Shrubland and Desert Ecosystems
  • 333 Broadway SE. Suite 115
  • Albuquerque, NM 87102-3497
  • 505-724-3660
  • 505-724-3688 (fax)
You are here: Grassland, Shrubland and Desert Ecosystems / Research by Project / Classical Biological Control of Toadflax

Classical Biological Control of Toadflax

Project Title

Classical Biological Control of Dalmatian (Linaria dalmatica), Yellow (L. vulgaris) and Hybrid (L. dalmatica x L. vulgaris) Toadflax


Dalmatian toadflax (DT) and yellow toadflax (YT) are listed among the top ten noxious weeds in multiple western U.S. states. Resource and land managers are challenged by the extent and severity of DT and YT invasions, particularly in fire-affected habitats. Toadflax infestations directly impact forage availability and quality on public land, an economically critical resource for Western cattle producers. However, the scale of the problem and environmental concerns, including negative non-target effects on native vegetation, frequently prohibit the use of herbicides and other conventional weed management strategies. Insect biocontrol represents a potential solution to these challenges, with the stem-mining weevil Mecinus janthinus (MJ) currently considered the most effective agent against DT. Long-term monitoring of agent and vegetation community dynamics on MJ release sites has been undertaken to better understand inconsistent control attained by MJ and to determine the operational efficacy of this agent across a range of invaded habitats. Additional studies are underway to evaluate the potential role of inundative releases of MJ, specifically to manage widespread DT infestations that frequently follow prescribed burns or wildfire.

Because infestations of yellow toadflax (YT) are widespread and have seldom been satisfactorily controlled by herbicide, they are considered one of the most challenging invasive weed management issues in the intermountain West. Biological control efforts to date against YT have met with minimal success; continuing the search for an effective agent has therefore been prioritized. CABI-Switzerland collaborators have identified and collected five new candidate agent species in the target weed’s native range. Host selectivity testing has progressed to varying degrees but requires additional testing in North American quarantine facilities and in limited initial field releases. This project is being coordinated through the North American Toadflax Consortium, a group of North American university and agency researchers and land management entities. An initial host plant test list for invasive toadflax has been produced for submission to the USDA APHIS Technical Advisory Group to support future petitions for environmental releases of new YT agents.

The recent discovery of host-specific biotypes of Mecinus janthinus (MJ) established on Dalmatian toadflax (MJ-DT) and yellow toadflax (MJ-YT) in Montana, and the confirmation of naturally-occurring persistent hybrid toadflax (HT) populations in Montana and Idaho, represent significant complications for toadflax biocontrol efforts. However, these developments also provide a unique model system to explore mechanisms of plant-insect signaling and recognition, and the evolution of host-specific insect biotypes. Our research will explore this system to identify factors affecting the abundance and distribution of MJ populations released for biocontrol, including the extent of reproductive isolation between the two MJ biotypes, their behavior on DT, YT and HT, and the role of volatile and endogenous compounds in the preference and success of MJ-DT and MJ-YT on the two host toadflax species and their hybrids. This knowledge will greatly improve the odds of successful deployment of this beneficial insect.

Selected Publications

Adult toadflax stem mining weevils
Adult toadflax stem mining weevils (Mecinus janthinus) established on yellow toadflax near Ovando, MT

GSD Principal Investigators

Sing, Sharlene    Research Entomologist    406-994-5143

Cooperators and Sponsors

Checking for stem galls on plants exposed to the toadflax stem galling weevil
Checking dalmatian, yellow and hybrid toadflax for stem galls on plants exposed to the toadflax stem galling weevil Rhinusa pilosa, in the Montana State University quarantine facility
  • Tom Barbouletos, USDA Forest Service Forest Health Protection
  • Dan Bean, Colorado Department of Agriculture Palisade Insectary
  • Leah Compton, USDA Forest Service Beaverhead-Deerlodge NF
  • Rose De Clerck-Floate, Agriculture and Agri-Food Canada
  • Andre Gassmann, CABI International – Switzerland
  • Rich Hansen, USDA APHIS PPQ
  • Liz Hebertson, USDA Forest Service Forest Health Protection
  • Heidi Heyrend, USDA Forest Service Caribou-Targhee NF
  • Jim Jacobs, NRCS Montana
  • Diane Johnson, USDA Forest Service Helena NF
  • Carl Jorgensen, USDA Forest Service Forest Health Protection
  • Susan Lamont, USDA Forest Service Gallatin NF
  • Tom McClure, USDA Forest Service Forest Health Protection
  • Joseph Milan, BLM Boise ID
  • Hal Pearce, USDA Forest Service White River NF
  • Rob Progar, USDA Forest Service Pacific Northwest Research Station
  • Carol Randall, USDA Forest Service Forest Health Protection
  • Richard Reardon, USDA Forest Service Forest Health Protection FHTET
  • Ivo Tosevski, CABI International – Switzerland
  • Sarah Ward, Colorado State University
  • David Weaver, Montana State University

Related Links

Weed-fighting weevils make themselves at home in Montana

Adult toadflax stem galling weevil
Disturbance of the understory community is inherent in the processes of mechanical tree harvesting. Heavy equipment with rubber or tracked tires removes vegetation, creating paths of exposed mineral soils, which can be readily available for a plant invasion.