World's Most Popular Weed Killer Linked To Decline Of Honey Bees


Jonathan O'Callaghan

Senior Staff Writer


Vivian Abagiu/College of Natural Sciences/UT Austin

A study has found that the most commonly used weed killer in the world may be contributing to the global decline of honey bees and native bees.

Published in the journal Proceedings of the National Academy of Sciences and led by the University of Texas at Austin, the team found that the weed killer Roundup, manufactured by Monsanto, could be causing bee deaths.


In particular, it was the active ingredient glyphosate found inside the weed killer that was identified as the problem. While it is nontoxic to animals, the study discovered it interferes with an important enzyme found in plants and microorganisms.

“We need better guidelines for glyphosate use, especially regarding bee exposure, because right now the guidelines assume bees are not harmed by the herbicide,” Erick Motta, who led the research with professor Nancy Moran, said in a statement. “Our study shows that’s not true.”

To come to their conclusion, the team exposed honey bees to glyphosate levels found in crop fields. Monitoring the bees by painting their backs, they found that after three days their healthy gut microbiota had been significantly reduced. Half of their eight dominant species of healthy bacteria had been reduced, including one critical to processing food and fighting infections.

After eight days of the study, half of the bees with a healthy microbiome were still alive, but only a tenth of those exposed to glyphosate had survived. Thus, the researchers suggest that glyphosate should not be used on plants visited by bees.

The researchers marked the bees to track their progress. Vivian Abagiu/College of Natural Sciences/UT Austin

Responding to the research, Monsanto denied the accusations. “Claims that glyphosate has a negative impact on honey bees are simply not true,” a spokesperson told The Guardian. “No large-scale study has found any link between glyphosate and the decline of the honey bee population.”

They also suggested that “more than 40 years” of scientific evidence showed no risk to animals or the environment. But based on this latest study, it appears the effect on plants and microorganisms may have gone unnoticed until now.

Honey bees face an uncertain future, since the discovery of colony collapse disorder in 2006 when millions of bees disappeared in the US. Various factors have been identified as causing problems, including climate change, while the EU recently decided to ban a known bee-killing pesticide.

With a popular weed killer now also identified as a problem, hopefully further steps can be taken to save bee populations around the world. Because without bees, we’re pretty screwed.


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  • colony collapse disorder,

  • monsanto,

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