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UBC Theses and Dissertations

Agent-based scenario models of invasion and movement of rhagoletis pomonella (diptera: tephritidae) within the southern interior of British Columbia Muselle, Brian Thayer


The apple maggot, Rhagoletis pomonella, is an economically important native pest of pome fruits in the US and Canada. BC’s Okanagan Valley is currently the only significant commercial apple-producing region in North America that remains free of its impact. This is likely to change soon, as R. pomonella is well established within certain counties in adjacent Washington State. Extensive sampling and control efforts have been undertaken since the pest’s arrival in Washington in the late 1970s. Data from American agencies provided a foundation for spatially explicit agent-based models (ABM), which I developed and used to evaluate fly movement and establishment under different management scenarios within comparable regions in the Okanagan. ABMs enable simultaneous manipulation of agent behaviour (here, insect dispersal and human management practices) and other factors within a spatially explicit landscape context, in ways that would otherwise be infeasible to explore in the field. My objective was to use ABM simulations and their outcomes to inform future management and survey efforts in advance of R. pomonella establishing in the Okanagan. I first constructed a validation model situated in Washington State landscapes, informed by historical data from state agencies, and then a predictive model for Okanagan landscapes where R. pomonella has yet to establish. Using ABMs to simulate pest invasion in a new area is, to my knowledge, novel. I calibrated my model parameters using information from the literature and data describing historical spread in Washington. The Washington-based validation model yielded a 52.8 – 82.0% agreement for the locations of apple maggot infestation and a 52.1 – 81.9% agreement for the locations of apple maggot infestation severity. The predictive simulations within Okanagan landscapes yielded maps expressing risk of infestation under various management and spread scenarios. They showed the most important management strategy for reducing apple maggot infestation was public education. Management strategies aside, the simulations suggested that the Okanagan regions’ environment is not especially suitable for apple maggot establishment, though this finding should be considered preliminary. My research highlights key data gaps, and demonstrates the utility of ABMs for pest management scenario modeling.

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