Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2013
Publication Date: 3/31/2014
Citation: Hock, V., Chouinard, G., Lucas, E., Cormier, D., Leskey, T.C., Wright, S.E., Zhang, A., Pichette, A. 2014. Establishing abiotic and biotic factors necessary for reliable male pheromone production and attraction to pheromones by female plum curculios Conotrachelus nenuphar (Coleoptera: Curculionidae). The Canadian Entomologist. DOI: 10.4039/tce.2014.1. Interpretive Summary: The plum curculio (PC) is a destructive pest of stone and pome fruit in eastern North America. Both adult males and females feed on developing fruits and fruit buds. Adult females also lay eggs in developing fruit soon after petal fall. Subsequent larval feeding can lead to either severe scarring or fruit drop, capable of damaging 90% of fruit at harvest. There has been a great deal of effort directed toward development of trap-based monitoring systems for use against plum curculio in commercial orchards. A male-produced aggregation attractant has been reported to attract both sexes. However, the activity was not significant and consistent in field conditions. In order to determine which physiological factors influenced male attraction to females and female response to males, a series of laboratory bioassays has been conducted. We discovered that mating status, temperature, and humidity greatly influence the male pheromone production and female response. Information obtained from this study will help scientists and growers better understand the physiological life stages for PC and facilitate development of more efficient detection and monitoring tools for its management.
Technical Abstract: The plum curculio Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) is a key pest of stone and pome fruit. Though grandisoic acid was identified as a male-produced aggregation pheromone for this species, other components likely exist, as have been identified various curculionids. To determine these components an understanding of conditions necessary for optimum pheromone production/attraction is needed. Tests were conducted in a dual-choice still-air vertical olfactometer using live male plum curculios odour sources and live females responders, to determine which physiological factors influenced female response. For both strains the odor of two virgin males elicited significantly greater and consistent attraction from mature virgin females compared to the control. Head-space collections of grandisoic acid production under various conditions (flow rate/frequency, collection strata, humidity, temperature, harborage) revealed that plum curculio produce grandisoic acid under high humidity in the presence of fruit. EAGs revealed significant responses to Grandlures I, II, III/IV and the positive enantiomere grandisoic acid: the amplitude of the signal varied with concentration. Our data identify the optimal physiological state/conditions at which pheromone collections should be performed, and what life stages respond to these stimuli. These results have implications for optimizing monitoring tools for this crop pest.