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Earley, Nathan Gibson

University of British Columbia

In importation biological control, natural enemies (aka biocontrol agents) are released into the invaded range of a target pest species to regulate pest populations. Evaluating host specificity of candidate biocontrol agents is central to investigating agent suitability for release into target localities. Fundamental host range testing is a valuable tool for evaluating ecological risks associated with agent release. However, these tests often overestimate non-target attack in nature because laboratory testing fails to account for all natural processes limiting non-target host acceptance. In the Drosophila suzukii Matsumura (Diptera: Drosophilidae) biocontrol system, two parasitoids (Hymenoptera: Figitidae) with differing fundamental host range specificity are promising candidates for the control of this small fruit pest. Adventive populations of both parasitoids have recently been detected in southwestern British Columbia, offering a unique opportunity to investigate the ecological host range of the parasitoids before their proposed release. In Chapter 2, I extend host-specificity testing moving from classic fundamental host range testing towards more ecological host range testing. Here, I exposed non-target hosts to parasitoids in the laboratory in both artificial and more natural rearing media, and in field assays using recently established populations of the parasitoids. I show that parasitism rate is not affected by media type, but is affected by host species. Additionally, I quantify the host ranges of three potential D. suzukii biocontrol agents, using literature records. In Chapter 3, I investigate adventive parasitoid ovipositor morphology to identify possible morpho- logical constraints to host exploitation that may influence host specificity. Ovipositor morphology influences parasitoid access to hosts, and therefore influences parasitoid success. I dissected and measured ovipositors from populations of two adventive parasitoids reared from different sites and different fruits. I report differ- ences in ovipositor morphology between parasitoid species and discuss possible competitive outcomes that these differences impose. Quantifying the host specificity of biocontrol agents, and the factors that drive host specificity, is at the crux of effective biological control programs. My work improves our understanding of both, and contributes to global agro-ecosystem sustainability.

Text

2022-08-15

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82364

Biology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/