The honey bee (<i>Apis mellifera</i>) larval toxicity, repeated (chronic) exposure study is required by global authorities of pesticide regulation who must evaluate the impact of new chemistries on pupal survival through adult eclosion. The Pollinator Research Task Force partnered with 15 laboratories (conducting a total of 16 trials) to validate a proposed method based upon the current OECD Guidance Document (GD) 239 with modifications developed at the University of Florida. Each trial included five increasing test concentrations of a toxic reference (dimethoate), a 2% acetone (solvent) treatment group (the maximum concentration allowed according to OECD GD 239), and a water control. The data were anonymized by an independent data consultant (Pacific EcoRisk) and reviewed by a committee consisting of one representative each from industry, academia, and government. Out of the 16 conducted trials, 13 (81.25%) generated data that met the current OECD GD 239 validity criteria of ≥ 70% survival at adult eclosion in the water controls. The 2% acetone group yielded poor survival and only 41.7% (5/16) of the laboratories had greater than 70% survival. A dimethoate concentration of 24 µg a.s./g diet (ppm) was determined to be satisfactory as a positive control (i.e.  ≥ 50% mortality of treated individuals) as required by the current OECD GD 239. Environmental conditions for the trials were difficult to standardize across laboratories, but no apparent association was observed between environmental deviations and test performance. In conclusion, the ring test confirmed high control survival and consistent toxicity from the positive control across the majority of participating laboratories. Acetone should not be used at the maximum concentration allowed by OECD GD 239 (2%) due to high mortality in the developing bees at this concentration. The ring test successfully validated the study protocol and can be used to support global regulatory authorities when developing and finalizing honey bee test guidelines. <br/>

Validation of the 22-day honey bee larval toxicity, repeated (chronic) exposure study design

254th National Meeting (2017)

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