Post-release monitoring of biological control agents against Alliaria petiolata in Canada
Alliaria petiolata (Brassicaceae) is native to the EPPO region and an invasive alien plant in Canada and the USA. It is a biennial species which in the first year forms a rosette and in the second year develops a stem and flowers. In North America it has negative impacts on biodiversity and ecosystem services where it can outcompete native plants and alter soil microorganisms and nutrient cycling through allelopathic effects. In Canada in 2023, Ceutorhynchus scrobricollis (Coleoptera: Curculionidae) was released as a biological control agent against A. petiolata at field sites in Ontario, British Columbia, and Alberta. A post-release monitoring programme was established to assess the effectiveness of the agent and during this monitoring programme a native beetle, Mordellina ancilla (Coleoptera: Mordellidae), was observed in A. petiolata stems. Further surveys revealed that M. ancilla was a widespread stem-borer in late second year and dead A. petiolata plants. The observed life cycle of M. ancilla indicates that it is unlikely to negatively impact the growth and reproduction of A. petiolata and it is unlikely to affect the use of C. scrobricollis as a biological control agent.
Sources
Hall TCK, McTavish MJ, Boutchier RS, Smith SM (2025) First record of the native beetle Mordellina ancilla (Coleoptera: Mordellidae) in association with introduced garlic mustard (Brassicaceae) in Ontario, Canada. The Canadian Entomologist 157, e19, 1-12. https://doi.org/10.4039/tce.2025.7