Response of Adult Plum Curculios (Coleoptera: Curculionidae) to Contrasting Shades in Field and Laboratory Experiments.

Abstract

The responses of adult plum curculios, Conotrachelus nenuphar (Herbst), to visual stimuli were assessed in field and laboratory conditions to evaluate the hypothesis that adult captures should increase when traps visually contrast with a lighter horizon, such as the sky. Release-recapture field studies tested whether adult responses to traps were influenced by the trap's visual contrast with background on the horizon. Results at four sites showed that significantly more adults were captured in traps with woodlots behind them, refuting the hypothesis. Laboratory tests in environmental conditions of 315 lux or less observed the movement of adults between intervals. These showed that significantly more females and males relocated in areas marked with black. This effect occurred when adults were presented with black surfaces, stripes, or lines. The black shade used correlated with lower reflected lux (<110), and when in conditions of ≤ 10 lux, significant adult relocation on black was not observed. These results suggest that adults arrest in or move toward areas with low reflected lux. The laboratory and field results combined suggest that higher adult captures in traps correlated with the largest areas of low lux on the horizon. The results imply that trap placement should take reflected lux from all nearby objects into account and that even in small patterns on traps, variance in shade or reflected lux may permit manipulation of plum curculio movement.