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The world's most widely used weed killer also may be killing bees indirectly, as research from the University of Texas, Austin, shows that honey bees exposed to glyphosate lose some of the beneficial bacteria in their guts and are more susceptible to infection and death from harmful bacteria.

"We need better guidelines for glyphosate use, especially regarding bee exposure because, right now, the guidelines assume bees are not harmed by the herbicide. Our study shows that's not true," says Erick Motta, a graduate student in integrative biology who led the research, along with evolutionary biologist Nancy Moran and Kasie Raymann, a former postdoctoral researcher in Moran's lab and now an assistant professor at the University of North Carolina, Greensboro.

Because glyphosate interferes with an important enzyme found in plants and microorganisms, but not in animals, it long has been assumed to be nontoxic to animals, including humans and bees. However, this study shows that, by altering a bee's gut microbiome--the ecosystem of bacteria living in the digestive tract, including those that protect it from harmful bacteria--glyphosate compromises its ability to fight infection.

Bees with impaired gut microbiomes are far more likely to die when exposed to Serratia marcescens, which is a widespread opportunistic pathogen that infects bees around the world.

"Studies in humans, bees, and other animals have shown that the gut microbiome is a stable community that resists infection by opportunistic invaders," explains Moran. "So, if you disrupt the normal, stable community, you are more susceptible to this invasion of pathogens."

Based on their results, Motta and Moran recommend that farmers, landscapers, and homeowners avoid spraying glyphosate-based herbicides on flowering plants that bees are likely to visit.

More than a decade ago, U.S. beekeepers began finding their hives decimated by what became known as colony collapse disorder. Millions of bees mysteriously disappeared, leaving farms with fewer pollinators for crops. Explanations for the phenomenon have included exposure to pesticides or antibiotics, habitat loss, and bacterial infections. This latest study adds herbicides as a possible contributing factor.

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Title Annotation:COLONY COLLAPSE; glyphosate
Publication:USA Today (Magazine)
Geographic Code:1USA
Date:Jun 1, 2019
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