1-octadecene, A Female Produced Aggregation Pheromone of the Coffee White Stem Borer (Xylotrechus quadripes)

Abstract

Coffee white stem borer, Xylotrechus quadripes is a serious insect pest of coffee across the world. Pheromone traps baited with male produced 2-hydroxy- 3-decanone (2H3D) attracted females, and also males. Interestingly, a pair of males and females in a cage attracted more beetles compared to 2H3D traps. We hypothesized volatiles emitted from females are perceived by males. Volatiles from females were collected through the air entrainment method and identified 1-octadecene by using gas chromatography coupled with mass spectrometry. Release of 1-octadecene was female specific, however, both male and female antennae elicited responses in chromatography-electroantennography. Electroantennogram responses were dose-dependent in both sexes and were higher in the antennae of females. Combination of male pheromone component 2H3D, and female produced 1-octadecene at 1:2 ratio increased both male (0.69 ± 0.13; mean ± SEM in -mV) and female (0.98 ± 0.20) antennal responses. Responses to constant doses of 2H3D and increasing doses of 1-octadecene (1:4, 1:6, 1:8, 1:10) were not different from male pheromone alone. Beetle captures to male pheromone alone at 3 different doses (75, 150 and 300 mg) were not significantly different from a pair of live beetle traps. A blend of 2H3D and 1-octadecene at 1:2 ratio trapped more beetles (3.50 ± 0.65; mean ± SEM) over 2H3D alone (2.00 ± 0.82), overall, our experiments suggest 1-octadecene is an aggregation pheromone. Our results support the hypothesis that males use 1-octadecene in mate finding, and potential to use it for monitoring and mass trapping.

This research was partially funded by the Central Coffee Research Institute RES/CCRI/Ento-PCI/2011-15/1674 and the APC was covered by the authors. PM was awarded Rajiv Gandhi National Fellowship to pursue PhD from 2011–2014 by the University Grants Commission funded by Ministry of Social Justice & Empowerment and Ministry of Tribal Affairs, India.