How can pesticides affect honeybees?

How can pesticides affect honeybees?

Pesticides are used worldwide in agriculture because of their effectiveness in controlling pests.  However, they can also affect honeybees by direct topical contact or through secondary exposure via the consumption of contaminated pollen, nectar, or water.  Exposure to pesticides, together with disease and habitat loss, are the most commonly cited factors in the current decline of honeybee populations.

This risk-to-bees evaluation is based on the incidence of exposure to and the toxicity of common pesticides. In the paper, investigators aimed to understand the relationship between the sublethal pesticide exposure and the toxicity and management of honeybees. They analyzed the published literature to collate a meta-data set of pesticide specific LD50 for honeybees.

The damaging effects of sublethal pesticide exposure, not only to reproduction, but also to the physiology, and cognition of honeybees is underlined throughout this paper. Exposure was also found to be largely immunosuppressive, leading to changes in the bees’ response to movement and flight and their susceptibility to pathogens.

It is clear that pesticides are negatively impacting honeybees but completely removing them from agriculture is not currently possible.  One alternative could be lactic acid bacteria (LAB) supplementation. The most common strategy is to add the bacteria to a sucrose-based syrup solution.  The full article explores this and other options. Some previous studies have demonstrated positive results for LAB supplementation in reducing pesticide absorption in honeybees.  It has also been shown to have a protective effect on the host.

We know a great deal about the sublethal effects of neonicotinoids, but not as much about other classes, particularly fungicides and herbicides. In addition to focusing more strongly in this area, the authors propose to further investigate the role of the microbiota in aiding host survival from pesticides and the ability for probiotics to mitigate their sublethal effects.

Chmiel JA, Daisley BA, Pitek AP, Thompson GJ and Reid G. Understanding the Effects of Sublethal Pesticide Exposure on Honey Bees: A Role for Probiotics as Mediators of Environmental Stress. Front. Ecol. Evol. 8:22 (2020). doi: 10.3389/fevo.2020.00022