To address new European Union (EU) data requirements for plant protection products, honey bee risk assessments are required where exposure of adults and larvae via direct contact or from residues in nectar and pollen cannot be excluded. Acute oral/contact toxicity studies are performed on adult bees and registrants may also be required to conduct Tier 1 larval chronic toxicity studies for which an OECD guidance is still under development or Tier 2 colony-level brood effects studies. For EU re-registration of glyphosate, potential exposure and effects on honey bee brood/colonies were assessed in separate studies. To quantify exposure, a greenhouse study involved a spray application of a glyphosate formulation to flowering Phacelia tanacetifolia during peak bee foraging. Glyphosate concentrations over time in forager-collected pollen and nectar were analysed. Mean glyphosate levels in nectar were >10X lower than in pollen and declined rapidly with DT50 values of 1-2 days. Pollen and nectar residue values were used as inputs to a bioenergetics-based exposure model to establish realistic worst case dose levels. To quantify effects on brood/colonies, a Tier 2 bee brood feeding study was performed using the Oomen test design. Colonies were tested at four dose levels including the control. Colonies were assessed 1 week prior and at weeks 1, 2, and 3 after dosing. Assessments tracked development of individual larvae and emergence, and the health of the colony as a whole with exposure confirmed by residue analysis of larvae collected from within the colony. No effects at any dose level were observed, consequently the No Observed Effect Level for brood development and adult survival was the highest dose tested, providing a sufficient margin of safety on the risk of glyphosate to honey bees. This conclusion is consistent with results of independently performed semi-field and field bee brood studies using a glyphosate-based formulation.

Addressing new data requirements for chronic honey bee testing in the EU

246th National Meeting (2013)

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