The miticide thymol in combination with trace levels of the neonicotinoid imidacloprid reduces visual learning performance in European honey bees (Apis mellifera)

Authors: COLIN, THEOTIME - Macquarie University; PLATH, JENNY - University Of Kassel; KLEIN, SIMON - Universite Paul Sabatier; VINE, PETA - Macquarie University; DEVAUD, JEAN-MARC - Universite Paul Sabatier; LIHOREAU, MATHIEU - Universite Paul Sabatier; Meikle, William; BARRON, ANDREW - Macquarie University

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2020
Publication Date: 2/27/2020
Citation: Colin, T., Plath, J.A., Klein, S.K., Vine, P., Devaud, J., Lihoreau, M., Meikle, W.G., Barron, A. 2020. The miticide thymol in combination with trace levels of the neonicotinoid imidacloprid reduces visual learning performance in European honey bees (Apis mellifera). Apidologie. 51:499-509. https://doi.org/10.1007/s13592-020-00737-6.
DOI: https://doi.org/10.1007/s13592-020-00737-6

Interpretive Summary: Honey bees are exposed to pesticides as they forage for nectar and pollen in the field. Beekeepers will also treat bees with pesticides to control mites in the hive. Both of these kinds of pesticides, as well as the interactions between pesticides, can have effects on bees. In this study bees were taught to pick a certain color (blue) by being given low shocks when they chose another color (green), after they had been exposed to very low levels of the two different kinds of pesticides. Because bees use visual cues to find flowers in the field, they are good at distinguishing colors. While bee learning was not affected by the field pesticide or the mite pesticide alone, the combination of the two kinds of pesticides did affect bee learning. This suggests that bee learning in the field may also be affected, and that foraging success of bee hives exposed to both kinds of pesticides might be reduced.

Technical Abstract: Despite growing concerns over the impacts of agricultural pesticides on honey bee health, miticides (a group of pesticides used within hives to kill bee parasites) have received little attention. We know very little about how miticides might affect bee cognition, particularly in interaction with other known stressors, such as crop insecticides. Visual learning is essential to foraging bees to find their way to flowers, recognize them, and fly back to the nest. Using a standardized aversive visual conditioning assay, we tested how field exposure to three pesticides affects visual learning in European honey bees (Apis mellifera). Our pesticides were two common miticides, thymol in the commercial formulation Apiguard® and tau-fluvalinate in the formulation Apistan® and one neonicotinoid, imidacloprid. We found no effect of miticides alone, nor of field-relevant doses of imidacloprid alone, but bees exposed to both thymol and imidacloprid showed reduced performance in the visual learning assay.