UBC Theses and Dissertations
Exposure to volatile organic compounds from peppermint as a management strategy for Drosophila suzukii Gowton, Chelsea Megan
Drosophila suzukii is an invasive fruit fly of agricultural concern as it is able to oviposit in ripening and fresh fruit. Olfactory signals in the form of volatile organic compounds (VOCs) may reduce D. suzukii attraction to hosts and decrease survival, but it is unknown how the efficacy of VOCs varies across D. suzukii life stages and how VOCs interact with cultural and biological controls. Peppermint essential oil and fresh peppermint (Mentha x piperita) produce VOCs and recent studies have shown peppermint essential oil to be effective at repelling adult D. suzukii. First, through a series of laboratory bioassays, we evaluated the joint effects of peppermint VOCs on D. suzukii survival and the survival of and parasitism rates by a pupal parasitoid wasp, Pachycrepoideus vindemmiae. We determined whether exposure to peppermint VOCs at the pupal stage reduced adult emergence, and whether this depended on environmental conditions (i.e. soil moisture). Then, we evaluated whether exposure to peppermint VOCs reduced or enhanced parasitism by the pupal parasitoid and whether this depended on the timing of peppermint VOC exposure (i.e. before, during, or after parasitism). Second, we used a intercropping field trial to determine whether intercropping with peppermint plants could reduce D. suzukii infestation in dropped blueberries. We used weekly baited fruit cages to monitor D. suzukii infestation and herbivory by other pests in both a peppermint intercrop and a conventional ryegrass/white clover mix. In our laboratory bioassays, we found that exposure to higher concentrations of peppermint VOCs reduced D. suzukii emergence under moist soil conditions and that this was similar to dry soil with no peppermint exposure. Peppermint VOCs were toxic to adult P. vindemmiae, but developing P. vindemmiae were unaffected by peppermint VOC exposure. In our field experiment, we found low D. suzukii infestations in both intercropping treatments. However we observed increased dropped fruit consumption by slugs, ground beetles and wasps, reducing D. suzukii host sites. Growers may utilize targeted peppermint VOC exposure or intercropping with peppermint to reduce D. suzukii infestation however, this could negatively impact populations of P. vindemmiae dependent on the timing of application.
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