EDITOR’S NOTE: This article originally stated that in addition to nicotine, caffeine was also effective. However, as this correction explains, that is not the case. The four substances that WERE found to be effective are nicotine, anabasine, thymol, and catalpol.

Sometimes tiny bits of toxic substances can actually be beneficial. In toxicology, this concept is called “hormesis.” Recently, scientists from the University of Massachusetts and Dartmouth College published an entomological example in Proceedings of the Royal Society B.

The researchers studied the interaction between plants, pollinators, and parasites, and they found that bumble bees that consumed some natural toxins found in plant nectar — including nicotine, which has been used for centuries as a natural pesticide — were less likely to be infected with a common intestinal parasite called Crithidia bombi.

“We found that eating some of these compounds reduced pathogen load in the bumble bee’s gut, which not only may help the individual bees, but likely reduced the pathogen Crithidia spore load in their feces, which in turn should lead to a lower likelihood of transmitting the disease to other bees,” said Lynn Adler, one of the co-authors. “Because plants just sit there and can’t run away from things that want to eat them, they have evolved to be amazing chemists. They make biological compounds called secondary metabolites, which are chemicals not involved in growth or reproduction, to protect themselves. They are amazing in the diversity of what they can produce for protecting themselves or for attracting pollinators.”

The results may have implications for growers who depend on pollinators, who may want to think about planting pollinator-friendly hedgerows and gardens containing plants that produce natural herbal remedies for some of the common parasites and diseases that ail bees and other pollinating insects.

“The more we look, the more we see that these compounds are in nectar and pollen too,” adler said. “With so many people looking at bee health these days, it’s taken a long time for us to realize that perhaps we should be paying attention to how floral secondary compounds mediate pollinator dynamics and their interactions with pathogens.”

Adler and her colleagues studied eight chemicals: nicotine and anabasine found in nectar of flowers in the tobacco family, caffeine from coffee and citrus nectar, amygdalin from almond nectar, aucubin and catalpol from turtlehead flowers, gallic acid from buckwheat nectar, and thymol from basswood tree nectar. Four of them — nicotine, anabasine, thymol, and catalpol — were found to be effective. Commercial honeybee growers already use thymol, found in thyme plants, to treat mite infestations.

“Our novel results highlight that secondary metabolites in floral nectar may play a vital role in reducing bee-parasite interactions,” said senior author Dartmouth Professor Rebecca Irwin.

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– Secondary metabolites in floral nectar reduce parasite infections in bumblebees