Electrophysiological and behavioural responses of the Eucalyptus weevil, Gonipterus platensis, to host plant volatiles

Abstract

Gonipterus spp. weevils (Coleoptera, Curculionidae) are pests of Eucalyptus stands in many world regions. Here, we determined the host plant volatiles that might mediate host selection behaviour in G. platensis. Eucalyptus globulus volatile organic compounds were collected by headspace solid-phase microextraction, monolithic material sorption extraction and simultaneous distillation–extraction. Gas chromatography–mass spectrometry/electroantennographic detection (GC–MS/EAD) was used to determine which compounds triggered antennal responses in the insect. Further chemical analysis of the extracted compounds was conducted using gas chromatography–mass spectrometry (GC/MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC/TOFMS). Gonipterus platensis antennal response was elicited by 51 host plant volatiles and was subsequently confirmed for 33 of these compounds using commercial standards. The behavioural response of G. platensis to individual compounds was assessed in a two-arm olfactometer with ten parallel walking chambers, coupled to video tracking and data analysis software. Weevils of known age, sex and mating status were tested. We identified eight kairomones and two allomones. The behavioural responses differed depending on insect sex and mating status. Three compounds attracted virgin females or both sexes: camphene, (+)-α-pinene and 2-phenylethanol and are potential candidates for application in integrated pest management approaches. Furthermore, the two allomones may have potential use for developing push–pull strategies.