Influence of Trap Apparent Silhouette, Canopy Cover and Their Interaction on the Capture of Forest Coleoptera

Bark beetles and woodboring beetles can be serious forest pests and are often monitored using semiochemical‐baited flight intercept traps. Although factors like trap placement and silhouette are known to influence beetle capture, the interaction of these variables remains poorly understood. We conducted a field trial in Ontario, Canada, using a 2 × 4 factorial design to assess the effect of forest canopy cover (open vs. closed) and trap silhouette (black, white, and clear intercept panel trap and black multiple‐funnel intercept traps) on beetle captures. We collected 15,388 bark and woodboring beetles and analysed results from four Scolytinae (Curculionidae) species and four Cerambycidae species (9906 and 5482 individuals captured respectively). Canopy cover often influenced trap capture, with traps placed under an open canopy capturing more individuals than those under a closed canopy. The size of this effect varied among trap silhouettes and species. The effect of trap silhouette also differed between canopy covers for several taxa, and the relative size of the canopy effect often depended on trap silhouettes. Multi‐funnel interception traps frequently performed well, particularly for several scolytines, but no single trap silhouette was uniformly superior across all species and canopy covers. These results show that the interaction between trap silhouette and placement with respect to canopy cover is taxon‐specific and that effective surveillance and monitoring programs should consider both factors jointly when optimizing trap deployment.