Trophic interactions between species in agroecosystems provide key regulation ecosystem services and therefore also determine the dynamics, robustness and resilience of service provision. To achieve international goals of reducing application of pesticides without compromising key provisioning ecosystem services such as crop yield, recent research attaches importance to the biological control potential of carabid beetles. However, apart from feeding on pest species and weed seeds, carabids also consume non-pest prey (alternative prey) such as collembolans and earthworms, which can play a contradictory role in the efficacy of pest and weed control. Most carabids are described as generalist predators, although some species appear to be predominantly carnivorous whereas others are rather strict granivorous. The trophic plasticity in omnivorous species i.e. how they switch between prey types according to environmental conditions is poorly understood. Here, we sampled carabid beetles in cereal fields in three regions in Austria and France. Regurgitates of individuals from the three most common species, Poecilus cupreus, Pterostichus melanarius, and Pseudoophonus rufipes, were screened with diagnostic PCR, targeting abundant cereal pest species, weed seeds and detritivorous non-pest prey groups. The outcomes of these analyses will contribute to a better prediction of pest and weed control ecosystem services provided by these carabid species and their specific role in the functioning of agroecosystems.