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Honey bee health and productivity in Ontario, Canada: a multifactorial epidemiological approach

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Title: Honey bee health and productivity in Ontario, Canada: a multifactorial epidemiological approach
Author: Guthrie, Alessia
Department: Department of Population Medicine
Program: Population Medicine
Advisor: Jones-Bitton, AndriaWilson, Jeff
Abstract: Beekeepers in Ontario, Canada experienced record-breaking winter losses in 2014, and an unexplained rise in honey bee mortality incident reports between 2012-2014. The purpose of this thesis was to improve the understanding of the beekeeping industry in Ontario, and identify disease, management, and spatial factors associated with in-season (i.e., non-winter) colony mortality. This retrospective cross-sectional study utilized data (2014) from an Ontario-wide survey of beekeepers, and spatial corn crop locations obtained from Agriculture and Agrifood Canada. Results of descriptive analyses showed that Varroa mites and queen supersedure were among the key self-reported challenges facing many responding beekeepers. Stratified results between small scale beekeepers (<50 colonies) versus commercial beekeepers (≥50 colonies), showed commercial beekeepers have significantly more years of experience and higher honey production. Total in-season colony loss (i.e., cumulative incidence of colony mortality) for the study population was 19.6% (978 dead colonies and 4,992 colonies at risk; 95% confidence interval (CI)=18.5-20.7%). In-season colony loss was significantly lower for beekeepers with >3 years of experience (versus ≤2 years; odds ratio (OR)=0.40; 95% CI=0.18-0.90), and those managing ≥2 yards (versus 1 yard; OR=0.37; 95% CI=0.17-0.80). Knowledge of Varroa presence significantly lowered the odds of in-season colony loss (OR=0.34; 95% CI=0.16-0.76). Additionally, colonies with queens that were 1-year old (OR=0.34; 95% CI=0.14-0.83) or ≥2 years old (OR=0.15; 95% CI=0.05-0.45) were associated with decreased odds of in-season colony loss compared to queens <1 year of age. In spatial analyses, the presence of corn (as a surrogate for neonicotinoid exposure) in the same 10 km2 quadrat of a yard was not significantly associated with in-season colony mortality. In summary, this thesis finds in-season colony loss to have significant associations with beekeeper and disease factors but does not support the role of corn exposure. This provides opportunities to actively support and improve colony health by focusing on increased beekeeper education, particularly for small-scale beekeepers, in the areas of disease management and queen health. Future research that includes surveillance of in-season loss over multiple years, for both small-scale and commercial beekeepers, would likely contribute to a better understanding of honey bee health in Ontario.
Date: 2018-08
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