Do Pesticides Have Different Risks for Non-Honey Bees?

As concerns for pollinators, especially honey bees, continue to grow in the eye of the public, interest from the science community has grown just as much to advance understanding of the many threats bees are facing. For instance, risk assessments have examined the ways in which honey bees can be exposed to pesticides whenever they’re used. However, such assessments have previously utilized honey bees as stand-ins for all types of bees. Bee species are much more varied than just the honey bee, and entomologists are working to improve risk assessments to consider the variations between the honey bee and its bumble, stingless, and solitary bee cousins.

When it comes to bumblebees, Dr. Angela Gradish, who is a research associate with the University of Guelph’s School of Environmental Sciences, says, “The most important thing honey bee risk assessments miss is the potential exposure of bumblebee queens to pesticides.” Whereas the queens of honey bee colonies live solely in their hive while the worker bees are out foraging, bumblebee queens actually spend large amounts of time outside the colony foraging. With honey bees as the standard, queens being directly exposed to pesticides isn’t considered during a risk assessment. “This is significant because the loss of a bumblebee queen means the potential loss of an entire bumblebee colony,” says Gradish.

Gradish was the lead writer for a report recently published in Environmental Entomology, which reviewed the existing research for bumblebee pesticide exposure and compared it with honey bees. Another key difference in the exposure risks of bumblebees and honey bees is the effect of pesticides on soil. Differentiating from honey bees, some bumblebees make nests in the soil and others hibernate in it, where queens can make contact with residue from pesticides.

While research has been recently examining certain pesticides’ toxicity to bumblebees and other non-honey bees, new research needs to better measure exposure levels out in the field. Per Gradish, “Risk is a function of both toxicity and exposure. So, without an understanding of exposure, we can’t estimate the risk of pesticides to bumblebees or determine if honey bee exposure estimates are similar to or protective of bumblebees.”

Research suggests bumblebees are more diverse compared to honey bees, comprising of roughly 250 different species, but there is still much to learn about them altogether. “For example, we generally don’t have much data on how much nectar or pollen individual bumblebee larvae or adults consume,” Gradish said. “But we need those data to estimate how much pesticide bumblebees may be consuming. So, before we can adapt the risk assessment process, we need to study and quantify some basic biological traits of bumblebees.”

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