A research team from the Department of Integrative Biology at the University of Texas in Austin has made an important contribution to the body of research seeking to answer this key question:

Is the world’s most heavily used pesticide (glyphosate) contributing to the widespread decline of honeybees and other pollinators?

Glyphosate is the #1 herbicide in the world by volume and sales. It is, in fact, by far the most widely and heavily applied pesticide worldwide, ever. Global use started a dramatic rise in 1996 after the approval of genetically-engineered, glyphosate-resistant crops that allowed spraying over the top of growing plants (for details, see this 2016 journal article).

Meanwhile, marked declines in populations of honeybees, and other domesticated and wild pollinators, began to be observed in the early to mid 2000s. Several factors, including neonicotinoid insecticides, have been implicated in the decline.

This new study took a closer look at glyphosate, and identified important sub-lethal effects on beneficial bacteria in the gut of honeybees. Just as the case with humans, the honeybee microbiome provides important immune support to the bees.

Glyphosate kills weeds, and other plants, vines, and trees, by targeting the EPSPS enzyme, which plays an important role in amino acid formulation in plants. It turns out some microorganisms utilize the EPSPS enzyme as well. The study reports that negative impacts from glyphosate exposure to non-target animals with bacterial symbionts has been observed before.

To test whether honeybees are susceptible to such sub-lethal effects, the research team exposed hundreds of adult worker bees from a single hive to two different levels of glyphosate, 5 mg/L and 10 mg/L. These amounts were selected to mimic known environmental exposures that occur when pollinators forage on weeds sprayed with glyphosate, which is generally around 1.4-7.6 mg/L. A third control group was exposed to a sterile sugar solution. All the bees were then returned to their original hive for observation.

A subset of each experimental group was selected for microbiome analysis. The size and composition of their gut bacteria was measured prior to reintroduction to their hive and three days post-exposure. Then, they looked at how this exposure impacted susceptibility to bacterial pathogens.

The key findings are that first, glyphosate exposure reduced the number and altered the distribution of gut bacteria, and second, the exposed bees were more likely to die when exposed to a commonly occurring bacterial pathogen.

This is yet another “unintended consequence” of GE Crops. Or, as one expert explained in a story on the research in the Guardian:

“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.” –Professor Dave Goulson, University of Sussex

Sources:

Damian Carrington, “Monsanto’s global weedkiller harms honeybees, research finds,” The Guardian, September 24, 2018.

Douglas Main, “Glyphosate Now the Most-Used Agricultural Chemical Ever,” Newsweek, February 2, 2016.

Erick V. S. Motta, Kasie Raymann, and Nancy A. Moran, “Glyphosate perturbs the gut microbiota of honey bees,” Proceedings of the National Academy of Science, September 24, 2018.