Chemical Fungicides Attract Bees

Recent research testing honeybees’ preference for sugar syrup with and without agricultural fungicides shows that the fungicide-laced syrup attracts more bees — implying that fungicides may have a bigger effect on honeybee populations than previously thought.

| Summer 2018

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

  • bee

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.






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