Buzz kill: Glyphosate weed-killer threatens bees in the EU, experts flag

18 Jan 2023 --- Bees may be at risk of exposure to glyphosate – an active ingredient most commonly used in weed killers from the EU – via contaminated wildflower nectar. This could exacerbate the problem of food insecurity, according to research conducted by Trinity College Dublin and Dublin City University (DCU) scientists and published in Heliyon.

The researchers recommend that an investigation be conducted into the use of glyphosate as a desiccant.

Glyphosate, intended only to kill plants, has been shown to harm the digestive systems of honeybees and bumblebees, making them more vulnerable to infections. It may also have other negative consequences.

“This is the first time glyphosate is reported in unsprayed wildflowers under conventional farming conditions, and while we need more research to find how much higher glyphosate concentrations would be indirectly sprayed on plants,” says Elena Zioga, first author of the research article, and Ph.D candidate in the School of Natural Sciences at Trinity College Dublin.

“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.”

Pesticides containing glyphosate as a systemic active ingredient are some of the most extensively used herbicides worldwide. After spraying, residues have been found in nectar and pollen collected by bees foraging on treated plants. 

The researchers’ findings suggest that offsite transport of glyphosate, used as a desiccant, contaminates pollen and nectar of non-target wild plant species. The transport could be attributed to spray drift, run-off, root uptake, environmental factors and agricultural practices.

Call for glyphosate investigation
Since this is the first time it has been reported in unsprayed wildflowers growing near sprayed fields, experts recommend expanding the research of glyphosate toxicity to more wild bee species.

“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,” Zioga adds.Samples were collected from oilseed rape and blackberry wildflowers.  

“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 to enable a greater evidence base for evaluation of the renewal of market authorization for glyphosate in the EU.”

Essentially, pollen and nectar were evaluated for glyphosate and aminomethylphosphonic acid (AMPA) residues. Key points of the research show that glyphosate applied as a desiccant was detected in wild plant nectar and pollen. No AMPA was detected in any of the samples.

Oilseed rape (OSR) was selected as the focal crop species, and Rubus fruticosus growing in the hedgerows surrounding the crop was chosen as the non-target plant species. 

Pollen loads were taken from honeybees and bumblebees foraging on the crop at the same time. Glyphosate and AMPA residues were extracted using acidified methanol, and their concentrations in the samples were determined by a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Glyphosate was detected in R. fruticosus nectar and pollen samples that were taken within two to seven days after the application on the crop.

Concerns over glyphosate
In recent years, the worldwide intensive use of glyphosate and its accumulation in the environment and edible products has raised major concerns about the noxious side effects of glyphosate and AMPA on plant, animal, and human health. 

Based on several publications about the potential chronic side effects of glyphosate-based products on human health, the World Health Organization reclassified the herbicide glyphosate as “probably” carcinogenic to humans in 2015. 

In addition, the sub-lethal effects caused by glyphosate on honeybees could reduce pollination services, which would impact worldwide food production.

Contaminated blackberry wildflowers
Farmed fields of oilseed rape and blackberry wildflowers were sampled from seven locations in East and South-East Ireland. Non-target flowering plants are a significant exposure route of bees to glyphosate.

“Glyphosate is the most frequently used weed killer 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 honey bee products, which suggests they could be harmful to honeybees and those eating the honey,” Zioga explained.

Glyphosate residues were found in the pollen and nectar of the blackberry flowers within a week after spraying took place in three of the tested locations. No residues were detected when the weed killer was used as a pre-or post-emergence spray on an oilseed rape crop (two months before sampling).

Meanwhile, the latest data from the US Food and Drug Administration on economically motivated adulteration of imported honey revealed that 10% of the tested samples were violative. The agency assessment showed that more than 70% of the honey consumed in the US is imported.Bees are most threatened by glyphosate contamination via non-target flowering plants.

Data collection method
In 2019, winter-planted OSR (WOR) and spring-planted OSR (SOR) flowers were collected for pollen and nectar extraction. That year, blackberry flowers from plants growing on the edges of the fields where OSR crops were cultivated were also collected for pollen and nectar extraction. 

In 2020, SOR flowers were collected for pollen extraction. 

A minimum of 1,000 flowers were collected from each plant species in each field during each sampling event to obtain sufficient nectar and pollen for chemical analysis (100 mg and 100 μL nectar). 

All samples were weighed and stored at -25 °C before analysis. Pollen pellets collected from each bee species were combined, and palynological analysis was performed. 

This research was supported by the Irish Department of Agriculture, Food and the Marine as part of the Protects Project. 

In related industry developments, Dalan Animal Health, a biotech company pioneering insect health, has been granted a conditional license for the vaccination of honeybees against American Foulbrood disease caused by Paenibacillus larvae. The vaccine is non-GMO and can be used in organic agriculture.

In addition, Dutch plant-based ingredients producer Fooditive is on track to begin large-scale production trials of the world’s first 100% bee-free honey next year. As well as providing all the benefits of traditional honey, this will address consumer concerns about animal welfare and sustainability.

By Inga de Jong