Response of adult plum curculios (Conotrachelus nenuphar) to contrasts in color and illuminance, suggesting push-pull strategies for monitoring and management

The responses of adult plum curculios, Conotrachelus nenuphar (Herbst), to contrasts in color and illuminance were assessed in field and laboratory conditions.  Release-recapture field studies tested whether adult response to each trap was influenced by the trap’s visual contrast with background on the horizon, and results at all four sites showed that significantly more adults exhibited positive taxis towards traps with woods behind than to traps contrasted against the sky.  Laboratory tests in environmental conditions of 315 lux or less recorded the movement of adults between intervals.  These showed that significantly more females and males exhibited positive taxis towards areas of black.  This effect occurred when adults were presented with black surfaces, stripes or lines.  The color black correlated with lower reflected illuminance (<110 lux), and when in conditions of ten lux or less, significant adult positive taxis towards black was not observed.  These results suggest that adults exhibit positive taxis towards areas of low illuminance, and that adults will move towards the largest areas of low illuminance on the horizon.  In future management, low-illuminance should be the standard for traps.  Applications of materials reflecting illuminance to orchards could also be used as part of a visual push-pull strategy to draw adults to trap trees or orchard perimeter for later destruction.