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WASHINGTON, Sept. 24 (Xinhua) – A study published Monday in the Proceedings of the National Academy of Sciences showed that the most used weed killer in the world could kill bees indirectly.
Scientists at the University of Texas at Austin discovered that bees exposed to glyphosate were losing some of the beneficial bacteria present in their intestines and were therefore more likely to be infected and deadly by harmful bacteria.
They felt that it was possible that glyphosate contributes to the decline of honey bees and native bees worldwide.
"We need better guidelines for the use of glyphosate, especially with regard to bee exposure, because the guidelines assume that the herbicide does not harm bees," Erick explains. Motta, graduate student and Nancy Moran, evolutionary biologist. "Our study shows that this is not true."
Glyphosate interferes with an important enzyme found in plants and microorganisms, but not in animals, it has long been assumed that it was not toxic to animals, including humans. and the bees.
But the new study suggests that glyphosate could alter the intestinal microbiome of bees, the ecosystem of bacteria living in the bee's digestive tract, including those that protect it from harmful bacteria, thus compromising the ability of the bee to fight against the infection.
Researchers exposed bees to glyphosate at known levels in crop fields, yards and roadsides. Three days later, they observed that the herbicide significantly reduced the healthy intestinal microbiota.
Of the eight dominant species of healthy bacteria in exposed bees, four were less abundant. According to the study, the most affected bacterial species, Snodgrassella alvi, is an essential microbe that helps bees to process food and defend against pathogens.
Bees with altered intestinal microbiomes are also much more likely to die when they are subsequently exposed to a common pathogen called Serratia marcescens, compared to bees with healthy intestines.
About half of the bees with a healthy microbiome were still alive eight days after exposure to the pathogen, whereas only about one-tenth of the bees whose microbiomes had been altered by exposure to the herbicide were still alive.
More than ten years ago, American beekeepers began to find their hives decimated by what was called the colony collapse disorder. Millions of bees have mysteriously disappeared, leaving holdings with fewer pollinators for crops.
"This is not the only cause of all these bee deaths, but it's certainly something that people should worry about because glyphosate is used everywhere," he said. Motta.
Native bumblebees have microbiomes similar to those of honey bees, so Mr. Moran said that it is likely that they would be affected by glyphosate in the same way.
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