Predator-prey interactions between Pterostichus melanarius and Sitona lineatus: Implications for conservation biological control

The pea leaf weevil Sitona lineatus L. (Coleoptera: Curulionidae), is an invasive, economic pest of leguminous crops across the Canadian Prairies and Northern Great Plains of North America. Despite the availability of various management tactics, no comprehensive integrated pest management (IPM) program currently exists to sustainably manage this pest. Ground beetles (Coleoptera: Carabidae) are among the most diverse and abundant arthropods in agroecosystems and include many omnivorous species that contribute to conservation biological control of herbivorous pests. Pterostichus melanarius (Ill.) (Coleoptera: Carabidae) is a widespread, non-native ground beetle in pulse agroecosystems across the Canadian Prairies. Pterostichus melanarius is an opportunistic generalist, which feeds primarily on invertebrates, and some plant material. Adult P. melanarius can consume over three times their body weight per day and can aggregate in agricultural fields, where pest densities are high. This study tested the predatory interactions between P. melanarius and S. lineatus through laboratory feeding assays at varying S. lineatus densities and developed multiplex PCR assay to identify S. lineatus DNA in the gut content of field collected P. melanarius. Pterostichus melanarius readily consumed S. lineatus in the laboratory and S. lineatus DNA was detected in the gut content of field collected P. melanarius across multiple pulse fields in Alberta, Canada. Results from this study confirm P. melanarius is a natural enemy of S. lineatus in its expanded range and will help inform the development of an IPM program for S. lineatus population management in Alberta.