Quantifying Species‐ and Community‐Level Predation by Carabids on Pests and Beneficials in Wheat and Beet Fields

In this study, we apply a hierarchical Bayesian model to quantify predation by carabid beetles at species and community levels across three cropping contexts: fodder beet, sugar beet, and winter wheat. Prey includes pests (aphids and slugs) and beneficial organisms (earthworms, springtails, and spiders). Model predictions indicate higher overall predation pressure in wheat than in beet. However, the median diet composition contains a larger share of pests in beet fields, whereas consumption of earthworms and spiders is greater in wheat. The strongest diet shifts among cropping contexts occur in smaller carabids (genera Bembidion Latreille, 1802 [Carabidae: Bembidiini] and Trechus Clairville, 1806 [Carabidae: Trechini]), whereas larger species ( Pterostichus melanarius [Illiger, 1798] [Carabidae: Pterostichini], Pseudoophonus rufipes [De Geer, 1774] [Carabidae: Harpalini], and Poecilus cupreus [Linnaeus, 1758] [Carabidae: Pterostichini]) show more stable diets. Although community structure (species and relative abundances) differs markedly between wheat and beet, it does not appear to be the main driver of the community‐level predation indicator. Overall, our results support a higher potential for aphid biocontrol by carabid communities in sugar beet, with a lower collateral impact on earthworms and spiders.