Pesticides and honey bee mass mortality

Researchers identify a pesticide potentially responsible for historical mass honey bee mortalities. Mass honey bee mortalities occurred in France in the 1990s following the introduction of two pesticides, imidacloprid and fipronil. The former compound was initially thought to be the causal agent, but laboratory studies combined with modeling simulations point to the latter being more likely involved in honey bee deaths. Philippa Holder and colleagues measured dose-dependent mortality rates for imidacloprid, fipronil, and two other widely used pesticides in bees from outdoor hives, and used the data to model colony-level effects in demographic simulations. The simulations predicted 4,000-9,000 more bee deaths than control conditions during the first week of fipronil exposure, leading to colony collapse within 2 or 3 weeks. None of the other pesticides resulted in mortality sufficient to cause colony collapse. The authors employed two assays, recommended by proposed international regulatory guidelines, for determining the ability of potentially toxic compounds to bioaccumulate. Fipronil exhibited signs of toxic bioaccumulation in both assays, whereas the other pesticides showed no signs of bioaccumulation in either assay. The authors found that toxic fipronil metabolites from a single meal persisted in honey bees for at least 6 days. The results implicate fipronil as a potential cause of the mass honey bee mortalities in France in the 1990s and demonstrate the value of the proposed bioassays for identifying harmful bioaccumulative substances, according to the authors.

Article #18-04934: "Fipronil pesticide as a suspect in historical mass mortalities of honey bees," by Philippa J. Holder, Ainsley Jones, Charles R. Tyler, and James E. Cresswell.

MEDIA CONTACT: Philippa J. Holder, Newcastle University, UNITED KINGDOM; tel: +44-1914355869; e-mail: Philippa.Holder@Newcastle.ac.uk

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