Field and cage studies show no effects of exposure to flonicamid on honey bees at field-relevant concentrations

Authors: Meikle, William; Weiss, Milagra

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2022
Publication Date: 9/16/2022
Citation: Meikle, W.G., Weiss, M. 2022. Field and cage studies show no effects of exposure to flonicamid on honey bees at field-relevant concentrations. Insects. 13(9). Article 845. https://doi.org/10.3390/insects13090845.
DOI: https://doi.org/10.3390/insects13090845

Interpretive Summary: The effects of pesticides on honey bees is of great concern to beekeepers and general public. In particular, a class of pesticides called neonicotinoids has been found in some studies to affect bee learning and colony function. We had found a pesticide classified as a neonicotinoid, flonicamid, in the residue analyses of honey and pollen studies for a now published study, and we tested that at three different concentrations (0, 50 and 250 parts per billion) in sugar syrup in one field study with bee colonies and two cage studies. We measured colony population levels, hive weight changes, thermoregulation and CO2 concentrations in the field study, and we measured syrup consumption, thermoregulation and survivorship in the cage studies. Among all these measurements, we did not find any signficant treatment effects from the pesticide. We think this indicates that the pesticide is largely safe for honey bees at these concentrations, and that it is important to publish such results when they occur so people use safe pesticides when they need pesticides. Whether it is safe for other pollinators, like butterflies and solitary bees, was not explored in this work.

Technical Abstract: The effects of long-term exposure on honey bees to sublethal concentrations of flonicamid, a pyridinecarboxamide compound used as a systemic insecticide against sucking insects, were examined in a field study and two cage studies. The field study involved the continuous weight, temperature and CO2 monitoring of 18 honey bee colonies, 6 of which were exposed, over a six week feeding period, to 50 ppb flonicamid in sugar syrup, 6 exposed to 250 ppb flonicamid, and 6 exposed to unadulterated syrup (control). Treatment concentrations had been derived from observed concentrations in honey samples collected from a commercial apiary. Honey samples taken after treatment confirmed that colonies were exposed to those flonicamid concentrations. No effects of treatment were observed with respect to foraging activity, hive weight gain, thermoregulation or average CO2 concentrations. However, Varroa mite infestations may have also contributed to experimental variability. The two cage studies, in which cages (200 newly-emerged bees in each) were exposed to the same flonicamid concentrations and kept in a variable-temperature incubator, likewise did not show any experiment-wide effects with respect to survivorship, thermoregulation, or syrup consumption. These results suggest that field applications of flonicamid that result in concentrations as high as 250 ppb in honey may be largely safe for honey bees.