The risk assessment paradigm for honey bees in North America utilizes a tiered system. In the first tier, hazard values are derived from laboratory studies which employ artificial conditions that do not represent real world exposure scenarios. Hazard value refinements in the second tier involve tests of functional honey bee colonies using more relevant, although exaggerated, exposure scenarios. The colony feeding study design is a higher tier honey bee chronic effects test that exposes colonies via feeding with spiked food resources, typically a nectar substitute. The effects of clothianidin exposure on honey bee colonies were investigated with this design in two separate studies conducted beginning in 2014 and 2016. in each study colonies were exposed to one of five treatment levels of clothianidin (10 to 160 ppb) in 24-26.5 L of sucrose solution which was supplied to colonies inside the hive for six weeks. Control colonies received untreated sucrose. Hives were placed in one of twelve separate apiaries in a randomized block design. Honey bees were allowed to forage freely throughout the duration of the study. Exposure occurred during the summer in which a dearth of floral resources was expected in order to increase consumption of treated solution. Colony condition assessments were performed at various time points before, during the exposure, after the exposure until October. Effects on colony strength parameters (e.g., brood, food stores) were measured that allowed calculation of NOAECs and characterization of response curves. Comparisons of results from the two studies revealed consistent responses of the colonies to clothianidin exposure. Derivation of a colony-level NOAEC (19 ppb) which is directly comparable to residue studies allows for a refined and more environmentally-relevant risk assessment. Strengths and weaknesses of this study design will be presented along with potential research avenues to improve the understanding of pesticide risks to honey bees at the colony level.

Characterizing chronic toxicity to honey bee colonies with a colony feeding study design

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.