The world’s most used weedkiller damages the beneficial bacteria in the guts of honeybees and makes them more prone to deadly infections, new research has found.

Previous studies have shown that pesticides such as neonicotinoids cause harm to bees, whose pollination is vital to about three-quarters of all food crops. Glyphosate, manufactured by Monsanto, targets an enzyme only found in plants and bacteria.

However, the new study shows that glyphosate damages the microbiota that honeybees need to grow and to fight off pathogens. The findings show glyphosate, the most used agricultural chemical ever, may be contributing to the global decline in bees, along with the loss of habitat.

“We demonstrated that the abundances of dominant gut microbiota species are decreased in bees exposed to glyphosate at concentrations documented in the environment,” said Erick Motta and colleagues from University of Texas at Austin in their new paper. They found that young worker bees exposed to glyphosate exposure died more often when later exposed to a common bacterium.

Other research, from China and published in July, showed that honeybee larvae grew more slowly and died more often when exposed to glyphosate. An earlier study, in 2015, showed the exposure of adult bees to the herbicide at levels found in fields “impairs the cognitive capacities needed for a successful return to the hive”.

“The biggest impact of glyphosate on bees is the destruction of the wildflowers on which they depend,” said Matt Sharlow, at conservation group Buglife. “Evidence to date suggests direct toxicity to bees is fairly low, however the new study clearly demonstrates that pesticide use can have significant unintended consequences.”

Prof Dave Goulson, at the University of Sussex, said: “It now seems that we have to add glyphosate to the list of problems that bees face. This study is also further evidence that the landscape-scale application of large quantities of pesticides has negative consequences that are often hard to predict.”