Chemical Fungicides Attract Bees

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Photo by GettyImages/Photografiero
Bee on a spring flower collecting pollen and nectar

Bees, like humans, might be all too attracted to what’s toxic for them. Research recently published in Scientific Reports reveals that honeybees show a preference for collecting fungicide-laced sugar syrup, even though the substance often leads to significant problems within their hives.

The groundbreaking study specifically highlights the dangers of chlorothalonil, a fungicide that’s been linked to declining populations of numerous bee species. Previous research shows that the toxin increases the risk of fungal parasites for bees, and it might limit their ability to fend off low doses of other pesticides that wouldn’t otherwise be harmful.

Over the course of the study, researchers offered bees a choice between two sugar-water feeders. The first was laced with various types and concentrations of naturally occurring phytochemicals, fungicides, or herbicides, depending on the trial, and the second feeder was a control containing only sugar water. In free-flight conditions, the bees visited the fungicide-laced feeder more frequently than the control feeder, and drank more from it at each visit.

Overall, the bees showed the strongest preference for two samples: sugar water laced with low concentrations of chlorothalonil, and sugar water laced with the herbicide glyphosate. These results suggest that bees were not only failing to avoid herbicides and fungicides, but were actively seeking them out, at least at certain concentrations.

Why would bees show a preference for potentially toxic compounds in their food? Part of the problem seems to be that bees are natural foragers. Hives thrive best when bees diversify their food sources, sampling from the wide variety of flowers that bloom over the course of a year. A willingness to seek out potential new food sources, unfortunately, seems to make bees more likely to bring toxic compounds back to the colony.

These findings challenge assumptions about how damaging agricultural chemicals are for bee populations, because they reveal that earlier reports likely underestimated the amounts that bees are ingesting. Previously, many scientists argued that fungicides weren’t a significant threat to bee populations, because they believed the insects could detect the compounds and therefore avoid them. This new research reveals that while bees can detect fungicides and herbicides, they prefer to bring the more contaminated nectar back to the hive.

This research is especially worrisome because the overall impact of these compounds on honeybee populations is currently unknown, and wild insects provide over half of global crop pollination. Herbicides and fungicides are relatively understudied, considering how frequently they’re found in the natural world today. In addition, because fungi are genetically closer to animals than to plants, fungicides likely have yet-unknown effects on the insects that are exposed to them.

During a time when domestic bees in North America are suffering from unprecedented colony collapse, protecting wild pollinator populations from potentially toxic compounds is more important than ever. To learn how you can support our beneficial pollinators, check out the Xerces Society website.

Mother Earth Gardener
Mother Earth Gardener
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