Wildflower nectar can expose bees to glyphosate

Bees may be at risk from exposure to glyphosate, an active ingredient in some of the EU’s most commonly used weedkillers, via contaminated wildflower nectar. This was according to new research from Trinity College Dublin and Dublin City University scientists.

Residues of glyphosate have previously been found in nectar and pollen collected by bees foraging on plants that have been selectively targeted with weedkiller, but this is the first time they have been reported in unsprayed wildflowers growing near sprayed fields.

And although glyphosate is intended to only kill plants, it has been shown to harm the digestive systems of honeybees and bumblebees, which makes them more vulnerable to infections, and it may have other negative consequences.

Elena Zioga, a doctoral candidate in the School of Natural Sciences at Trinity College Dublin, and first author of the research article, said this was the first time that glyphosate had been reported in unsprayed wildflowers under conventional farming conditions.

“While we need more research to find how much higher glyphosate concentrations would be in directly sprayed plants, we know wild bees and honeybees will visit the contaminated wildflowers to collect pollen and nectar.

“They will thus be exposed to glyphosate and that could impact their health and the critical pollination service they provide.

“Glyphosate is the most frequently used weedkiller within the EU and is also very common in other parts of the world. The residues we found in nectar in this study exceeded the European maximum permitted levels of glyphosate in honey and honeybee products, which suggests they could be harmful to honeybees and those eating the honey.”

Zioga sampled farmed fields of canola, as well as blackberry wildflowers growing nearby in seven different locations in east and south-east Ireland. In three of these locations, glyphosate residues were found in pollen and nectar of the blackberry flowers within a week after spraying took place. When the weedkiller was used as a pre- or post-emergence spray on an canola crop (two months before sampling), no residues were detected.

Zioga added: “Knowing that bees may be exposed to glyphosate residues in the environment makes it important that more research takes place to assess the glyphosate impact on more bee species.

“As an additional priority, we recommend the immediate investigation of glyphosate as a desiccant before harvesting crops to better understand how this impacts non-target flowering plants growing near crop fields.

“This will enable us to have a greater evidence base for evaluation of the renewal of market authorisation for glyphosate in the EU.”

ȊȲTrinity College Dublin. ‘Bees exposed to common weedkiller via wildflower nectar’. ScienceDaily, 17 January 2023. Visit bit.ly/3HvoSM6.