A new study linking glyphosate to a decline in bee health has drawn mixed reactions from the farming industry and lobby groups.
Researchers from the University of Texas, Austin, US, investigated whether exposure to glyphosate could alter the bacterial gut microbiome of honeybees.
The bacterial microbiome plays a number of roles in keeping bees healthy, such as helping defend them against harmful bacteria and resist disease.
The researchers found that honeybees exposed to glyphosate lose some of the beneficial bacteria in their guts, making them more susceptible to diseases or even death.
But the findings of the study, published in the journal Proceedings of the National Academy of Sciences, have been disputed by scientists.
Oliver Jones, associate professor of chemistry at RMIT University, Melbourne, Australia, said the doses of glyphosate used in the study were “rather high” and the exposures of bees (less than one day) were “relatively short-term”.
He added: “A confusing result is that the bees exposed to the highest does of glyphosate seem to show far fewer effects than those exposed to a lower dose after three days. This effect was shown to be reproducible, but not explained.”
“There are also countries, such as Australia, where glyphosate is used, but bees are generally doing well. I think the work is a potentially interesting piece of the overall puzzle of bee health, but not the whole picture.”
Andres Arce, evolutionary ecologist at Imperial College London, said: “Interestingly, bees that were not exposed to the pathogen showed comparable survival to bees that were never given glyphosate.”
Bayer rejects study
Glyphosate is the active ingredient in Monsanto’s weedkiller Roundup, the most widely used herbicide in the world.
Bayer CropScience, which now owns Monsanto, said the study failed to establish a relationship between glyphosate and gut microbe problems in bees.
“Claims that glyphosate has a negative impact on honeybees are simply not true,” said a Bayer spokesman.
“More than 40 years of robust, independent scientific evidence shows that if applied according to label instructions, it is safe for use and poses no unacceptable risk for humans, animals and the environment generally.”