COMMON WEED KILLER LINKED TO BEE DEATHS.

• Position: COLONY COLLAPSE - Glyphosate

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...