A tiered approach to pesticide risk assessments for honeybees (Apis mellifera) includes a change in testing from the individual bee to the colony level as the assessment transitions from the lower to the higher tiers of refinement.  Imidacloprid is classified as highly toxic to the honeybee following acute contact or oral exposure based on laboratory studies of individual adult bee mortality.  Imidacloprid is also persistent and has been shown in various open literature papers to elicit sublethal effects, including impacts on individual bee behavior.  Because there is uncertainty associated with the impact of these combined effects at the whole-colony level, an open field feeding study was initiated in 2013 to evaluate the impact of long-term exposure to a range of imidacloprid concentrations in sucrose solutions. This poster provides the basic design and preliminary results from the feeding study, which evaluates the potential for dietary exposure to imidacloprid to significantly affect measurement endpoints at the colony level.  Colony condition (e.g., relative quantity of eggs, capped and uncapped cells containing larvae and pupae, pollen and nectar stores, and hive weight) was assessed at various points before, during, and after the 6-wk exposure period and includes overwintering.  The study design, while considered as Tier II and intermediate between laboratory-based studies and full-field studies, provides hypothesis-based toxicity data (e.g., no-observed adverse effect level) for comparison to exposure data collected in field plant residue trials and can be used to characterize the potential for pesticides to affect bee colonies.

Open field feeding study design with <i>Apis mellifera</i> to evaluate the whole-hive toxicity of imidacloprid at multiple concentrations in sucrose solution

248th National Meeting (2014)

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Open field feeding study design with Apis mellifera to evaluate the whole-hive toxicity of imidacloprid at multiple concentrations in sucrose solution