Identification and field verification of the aggregation pheromone components produced by male Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae)

Background: The chafer beetle, Holotrichia parallela, causes damage to numerous economically significant crops worldwide. Adult beetles exhibit aggregation behavior likely mediated by a male-produced pheromone. Advancements in biological research technology have facilitated the identification of insect aggregation pheromones and promoted their applications as bait for trapping and monitoring pests. Currently, only a few active components of aggregation pheromones from Holotrichia species have been identified. However, the specific components of aggregation pheromones produced by H. parallela remain unknown.

Result: In this study, we initially observed from Y-tube olfactometer assays that both male and female H. parallela were significantly attracted to volatiles emitted by males, but not to those from females. We then collected hindgut crude extracts of male adults and carried out gas chromatography-mass spectrometry analysis to identify potential aggregation pheromone components. Pentadecyl acetate, cis-13-docosenol, and behenic acid were identified as male-specific compounds in comparison to female extracts, serving as components of the aggregation pheromone in H. parallela. We further evaluated their attractiveness to H. parallea in both laboratory and field experiments. In laboratory settings, pentadecyl acetate, cis-13-docosenol, and behenic acid evoked significant responses to both males and females at specific concentrations, as evidenced by both electroantennography tests and behavioral bioassays. Under field conditions, traps baited with these three compounds captured significantly more H. parallela adults compared to control traps.

Conclusion: In this study, we found that pentadecyl acetate, cis-13-docosenol, and behenic acid are specifically present in male H. parallela, serving as aggregation pheromones. Both laboratory and field-trapping experiments suggest their potential as monitoring and controlling tools against H. parallela adults. © 2024 Society of Chemical Industry.