Chemical signatures affecting host choice in the Eucalyptus herbivore, Gonipterus sp. (Curculionidae: Coleoptera)

Abstract

Abstract-It is well-known that herbivorous insects respond to host plant volatiles. Yet details of how these insects perceive the complex profile of volatiles from different potential host plants has not been studied for most insects. Gonipterus spp. are important pests of Eucalyptus worldwide, but differ in their preference for different species of this host. In this study we consider whether host volatiles affect the host choice for a Gonipterus sp., and we characterize the response of the female insect to the volatile profiles from these hosts in an electro-antennographic (EAG) experiment. We sampled volatiles from freshly damaged leaves of three Eucalyptus species, and analyzed the profiles by gas chromatography coupled to electroantennography (GC-EAD) and gas chromatography coupled to mass spectrometry (GC-MS). Female weevils gave a mixed range of electro-physiological responses to volatile puffs from leaves of different tree species. This suggests that differences in volatile profiles of different trees play a role in how these beetles discriminate between potential hosts. GC-EAD analysis showed that responses were as complex as the volatile chemical compositions of the leaves. A number of these chemicals were identified and responses were mostly due to general green leaf volatiles. This was also evident from the fact that the insects showed a markedly greater response to the total volatile profile from freshly damaged leaves for all species. The females of the Gonipterus sp. can therefore detect damaged leaves, which may indicate host quality. Host specificity information is further expected to lie in the relative differences in emission ratios and synergism between different host chemical compounds, rather than specific individual compounds.

Attractant Effect of Eucalyptus globulus (Labill) and Foeniculum vulgare (Mill.) Essential Oils on Aegorhinus superciliosus (Guérin) (Coleoptera: Curculionidae)

“…Eucalyptol and the E. globulus leaves volatile were electrophysiologically active in Gonipterus spp. females with a mean response of 0.76 mV (Bouwer et al 2014). The anethole results showed that the antennae of both sexes of A. superciliosus can perceive this compound with a response higher in females than males.…”

Coupled gas chromatographic-electroantennographic responses of Xanthogaleruca luteola (Müller) (Coleoptera: Chrysomelidae) to volatile organic compounds from Eucalyptus globulus extract

“…According to the literature, some secondary metabolites have been identified in E. globulus. These are characterized by the presence of mixtures of terpenes and terpenoids of C10 and C15 (Tyagi and Malik, 2011), which would be the main components of the essential oil, and are found in a variety of plant families in different ratios for each species (Külheim et al, 2011;Bouwer et al, 2014), the eucalyptus species produce a great variety of these volatile compounds in significant amounts, which accumulate in glands distributed in the parenchymal tissue and in the bark of the tree (Özgenc et al, 2017).…”

“…Several secondary metabolites produced and emitted by E. globulus specimens exert effects on insect physiology and behavior, playing an important role in the plant-insect interaction (Bouwer et al, 2014). In order to understand the role of volatile organic compounds emitted by E. globulus when the insect is attracted to this non host-plant, dichloromethane extracts of E. globulus were analyzed through gas chromatography-mass spectrometry to identify main compounds and extract's composition.…”

Olfactory responses of Anaphes nitens (Hymenoptera, Mymaridae) to host and habitat cues

“…He et al. 2000; Paiva & Mateus, 2012), and iv) γ ‐terpinene, a compound reported by Bouwer, Slippers, Wingfield and Rohwer (2014) as being the main responsible for the dissimilar susceptibility of Gonipterus sp. 2 to different host species.…”