Infected bees seek out medicinal flowers - study

© Nikola Solic
Bumblebees sickened by an intestinal parasite are apt to visit flowers containing nectar and pollen that have a medicinal effect, a new study reports, indicating the current decline in the bee population could be abated through beneficial plants.

Iridoid glycosides, or secondary metabloites found in floral nectar, reduce common parasites in bees, previous research has found. In this case, scientists from the University of Vermont, Dartmouth College, and the University of Colorado-Boulder increased concentrations of two iridoid glycosides – aucubin and catalpol – in turtlehead, a wetland plant frequented by bees in eastern North America. Some plants were given high volumes of iridoid glycosides, while the other half's iridoid glycosides were diluted with sugar water.

Parasitized bees -- afflicted with reproduction and foraging complications -- preferred the flower with the highest iridoid glycoside concentrations, the researchers found. Their results are being published in the journal Ecology.

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"We show that bees might be able to self-medicate, altering their foraging behavior when parasitized so as to maximize their consumption of beneficial plant secondary metabolite compounds," said senior author of the study, Rebecca Irwin, a faculty member at North Carolina State University who was formerly with Dartmouth, according to phys.org.

The research team also found that bees would carry more pollen to other flowers from plants with the highest concentrations of nectar iridoid glycosides.

"Secondary metabolites are commonly present in floral nectar and pollen, yet their functions are not well understood," said the study's lead author Leif Richardson, a former Dartmouth student now with the University of Vermont. "In this study, we show that these compounds could influence plant reproduction via complex suites of interactions involving not only pollinators but also their natural enemies."

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The numbers of bees, vital to the pollination process, are dwindling across the world thanks to habitat destruction, pesticide use, and disease. In May, the US Environmental Protection Agency announced new regulations on pesticide use that seek to protect managed bee populations during certain periods of the year.

The proposal is part of the Obama administration's National Strategy to Promote the Health of Honey Bees and Other Pollinators. The administration wants to spend upwards of $82.5 million on honeybee research in the upcoming budget year, more than double the current allocation of $34 million.