Unexpected new findings from researchers at Johns Hopkins University are indicating the world’s most commonly used herbicide appears to weaken the immune systems of insects. One experiment with mosquitos known to spread malaria suggests the chemical can increase the insect’s susceptibility to parasitic infection, possibly increasing risk of human disease transmission.
Glyphosate is a weed-killer that has been in wide agricultural use since the 1970s. It kills plants by disrupting a crucial metabolic process called the shikimate pathway. The pathway is only present in plants, so for many years glyphosate was thought to be an ideal herbicide – harmless to everything but plants.
Over recent years, however, concerns have been raised over the chemical’s effect on the surrounding environment and humans. Austria and Vietnam were two of the first countries to outright ban the herbicide, while several others are undergoing a staged phase-out of its use over the coming years.
The effects of glyphosate on insects is still a source of much debate. Studies have found the herbicide can disrupt gut bacteria in insects, and this can lead to behavioral or physiological changes. A new study is suggesting glyphosate could impair immunity in insects, and this may lead to damaging consequences for human health.
Our results are the first to show that contact exposure to either consumer or agricultural Roundup® products at label recommended concentrations can cause high levels of mortality in bumble bees. The consumer product Roundup® Ready‐To‐Use caused 94% mortality at the pre‐mixed concentration, and still caused significant mortality at a quarter strength. The agricultural product Roundup® ProActive also caused significant mortality, although over a longer time period. Interestingly, Roundup® No Glyphosate caused 96% mortality while the generic GBH Weedol® did not significantly increase mortality. Together, this demonstrates that the co‐formulants in these Roundup® products, not the active ingredient glyphosate, are driving mortality. We suggest that the mechanism driving this mortality may be surfactants in the formulations blocking the tracheal system of the bees, which is essential for gas exchange. Given the hazard demonstrated here with all tested Roundup® products, and the extensive exposure of bees to such GBHs world‐wide, GBHs may pose a high risk to bees, and thus may be an as yet unidentified driver of the bee declines that are occurring around the globe.