Biological control of yellow toadflax: Interactions between Rhinusa pilosa and macroherbivores

Effective management of yellow toadflax (Linaria vulgaris), a widespread invasive weed in western North America, increasingly relies on classical biological control. Rhinusa pilosa, a stem-galling weevil, has shown promise in reducing plant vigor and reproductive output. However, in many rangeland systems, toadflax infestations overlap with areas heavily used by large herbivores, including livestock and wild ungulates. This talk investigates whether macroherbivore activity affects the establishment and success of R. pilosa populations. Using field surveys and herbivore exclusion experiments, I evaluate how grazing and browsing pressure influence stem availability, gall formation, and agent persistence over time. Results suggest that vertebrate herbivory may alter plant architecture or remove stems before gall induction occurs, with implications for long-term biocontrol efficacy. Understanding how land use practices intersect with biological control efforts is essential for integrating weed suppression into multi-use landscapes.