Honey bee Large Colony Feeding Studies (LCFS) are conducted as a novel type of Tier II semi-field study for the determination of potential effects of pesticides on free-foraging whole colonies during and after dietary intake of a known pesticide concentration. This study design represents a progressively more realistic level of refinement compared to individual laboratory-based studies. However, observed winter losses of control colonies indicate that stressors other than pesticides, e.g. resource availability, weather, diseases and beekeeping activities, likely influence colony condition and overwintering survival, confounding the assessment of impacts caused by pesticides. In the current study commissioned by the Pollinator Research Task Force, we apply the mechanistic honey bee colony model BEEHAVE to simulate colony dynamics observed in negative control colonies from multiple colony feeding studies. In the modeling approach, factors impacting colonies can be fully controlled and their impacts on colony condition can be assessed systematically. Study data from control colonies in seven LCFS were available and colony condition data collected in summer and fall were analyzed for predictors of overwintering success of individual colonies. The BEEHAVE simulations were parameterized with apiary-specific data available from the studies, including landscape-level resource availability, weather, initial colony condition and feeding patterns. BEEHAVE was calibrated and validated to simulate reported colony condition across the study period. BEEHAVE simulations with different combinations of external factors were used to assess their importance for colony condition. Colony conditions at study initialization and feeding patterns both influenced the colony condition in the fall, and thus, the probability of overwintering survival. Model simulations with different colony feeding patterns and initial colony conditions were then used to quantitatively estimate colony-level outcomes under conditions deviating from those in the studies. These results provide insight into the importance of factors related to study conditions and can be used to improve and inform LCFS study designs. Pesticide effects can be included in future model analyses, and analyzed in the context of multiple factors that impact colony health and overwintering success.

Addressing multiple factors impacting honey bee colonies in large colony feeding studies with a mechanistic honey bee colony model

2019 Fall National Meeting

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