Queensland fruit fly-predator interaction: a chemical ecology perspective

Predator and prey commonly use infochemicals to detect each other and they are of paramount importance for survival. In terrestrial ecosystems, infochemicals are a vital source of information for a majority of organisms and are detected primarily through olfaction. Although a plethora of studies regarding predator-prey interactions exist, there is a paucity of information about predator-prey interactions in the Queensland fruit fly (Q-fly), Bactrocera tryoni (Froggatt) and the infochemicals used by the flies to detect predators and vice-versa. To date, there is no advancement in this field due to the lack of knowledge on natural predators of Q-flies. Chemical identification of infochemicals from predators or prey will facilitate study of predator-prey interaction and risk of predation, and when the prey are pests, will potentially provide environmentally friendly means of pest control. Studies in this thesis were conducted with the aim of identifying potential predators, understanding behaviours of Q-flies and selected predators and prospecting behaviour changing infochemicals involved in the interaction of Q-flies and their predators. We also aim to explore the use of predator-released kairomones in fruit fly management.

Four potential predators (3 spiders & 1 ant) were selected based on their prevalence in the natural habitat of Q-flies. Flies detected and responded differentially (motility, foraging & oviposition) to olfactory cues from selected predators. Subsequent investigations identified a compound from the headspace volatiles of green tree ants that repelled ovipositing flies. Simulated field trials demonstrated the effectiveness of the identified compound in repelling ovipositing Q-flies. Further, a chemically defined oviposition-stimulant of Q-fly was identified to aid in lab repellency and oviposition deterrent assays. Conclusively, the aims of the project were achieved by identifying repellents from predators and further the compounds were formulated as a possible pest control product and tested in the field.