Long-term dynamics of honey bee colonies following exposure to chemical stress

Authors: COLIN, THEOTIME - Macquarie University; Meikle, William; PATEN, AMY - Commonwealth Scientific And Industrial Research Organisation (CSIRO); BARRON, ANDREW - Macquarie University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2019
Publication Date: 8/10/2019
Citation: Colin, T., Meikle, W.G., Paten, A., Barron, A. 2019. Long-term dynamics of honey bee colonies following exposure to chemical stress. Science of the Total Environment. 677:660-670. https://doi.org/10.1016/j.scitotenv.2019.04.402.
DOI: https://doi.org/10.1016/j.scitotenv.2019.04.402

Interpretive Summary: Honey bees are often exposed to pesticides in the field as they forage for pollen and nectar. Honey bees are also often attacked by pests such as mites, and then are treated by beekeepers with pesticides to reduce the mite numbers. Both the field pesticides and the mite pesticides, and their interaction, may affect bee colony health. In this study bee hives in Sydney, Australia and near Tucson, AZ, were placed on scales, in order to continuously measure weight, and provided with sensors to monitor temperature. The hives were also inspected every 6 weeks to measure the amounts of adult bees and larvae. The field pesticide had both positive and negative effects on colony health and activity. The mite pesticide, thymol, had a negative effect on colony growth, and beekeepers should to consider colony size and brood levels before applying it. The most important message was that the differences between the environments in eastern Australia and southern Arizona played a large role in how colonies developed and how they reacted to the treatments. Treatment effects were low in Australia, where there is abundant natural forage, but high in Arizona desert, where natural forage is very seasonal. For this reason, researchers and beekeepers need to take into account location and environment when trying to understand the effects of pesticides on bees.

Technical Abstract: Pesticide residues have been linked to reduced bee health and increased honey bee colony failure. Most research to date has investigated the role of pesticides on individual honey bees, and it is still unclear how trace levels of pesticides change colony viability and productivity over seasonal time scales. To address this question, we exposed standard bee colonies to chemical stressors known for their negative effects on individual bees and measured the productivity of bee colonies across a whole year in two environments. In particular, we exposed hives to the neonicotinoid imidacloprid and to the acaricide thymol, and measured capped brood, bee and honey production, as well as the temperature and foraging force of the colonies. The effect imidacloprid on the colony dynamics strongly differed between the environments. Imidacloprid was associated with positive and negative effects, with long-term consequences on the colonies. Thymol was associated with short-term negative effects at both locations and may have affected colony survival at one location. The overall benefits of thymol for the colonies were unclear. We conclude evaluating the benefits of acaricide treatments at the colony level and the risks associated with pesticides in their environmental range of use would highly benefit honey bees worldwide.