A recent study, released July 10th, 2015 by researchers with the Department of Biodiversity and Experimental Biology at the University of Buenos Aires, reveals some of the possible long-term effects of glyphosate exposure on honeybees and the results are more bad news for the bees.
Glyphosate is a broad-spectrum systemic herbicide used to kill weeds, especially those that compete with commercial crops. It was discovered by a Monsanto chemist in the 1970’s and was soon introduced to the market as RoundUp. Glyphosate usage is on the rise thanks to Monsanto’s RoundUp Ready genetically modified crops, which are designed not to suffer any ill-effects from applications of glyphosate. In 2012, 280,000 tons of glyphosate were used on crops in the United States alone. Due to the practice of monoculture, the most popular method of application is aerial spraying, which allows the pesticide to drift beyond the targeted crops and into the surrounding environment.
Although glyphosate inhibits aromatic amino acid pathways found only in plants, fungi and microorganisms (and not in animals), studies have shown different negative effects in invertebrate and vertebrate species. In invertebrates, common application concentrations have been shown to cause growth deficit in earthworms. In vertebrates, studies indicate chronic exposure to glyphosate may negatively affect amphibians. Glyphosate testing on Apis mellifera (western or European honey bee) was performed for product approval but only focused only on lethal doses as a measure of acute exposure. Studies were not conducted to test the sub-lethal and possible prolonged effects of glyphosate on honeybees.
When agrochemicals with a high water solubility, such as glyphosate, are sprayed they may be present on flowers later visited bees. These chemicals may then be taken back to the hive, where resources can be stored and accumulated until needed by the colony. Therefore, agrochemicals stored in the hive could have subtle negative effects in the long term that may not be obvious in the short term.
Researchers decided to investigate these possible long-term effects. When 15-day-old honeybees were first evaluated, researchers looked for any change in their overall behavior as a result of exposure to different glyphosate concentrations. Food intake, mortality, locomotive and orientation activity did not vary and all bees, regardless of glyphosate exposure, showed similar behavioral responses and mortality rates.
However when the bees were evaluated for their sucrose sensitivities, the results were different. Bees exposed to glyphosate scored lower on these “taste tests” than bees that were not exposed. This suggests that bees raised with sub-lethal concentrations of glyphosate have an increased response threshold for sucrose. Likewise, their olfactory performance was also lower than that of the non-exposed bees. Test results showed that that prolonged exposure to sub-lethal concentrations of glyphosate during the first 15 days of life inhibited the bees’ ability to establish a connection between a scent and a reward.
The study also explored the effects of glyphosate on foraging behavior in honeybees. Bees would continuously visit and collect from feeders regardless of whether or not glyphosate was present. Bees would then return to their hives and relay information to other bees without any differences in behavior before or after glyphosate exposure. Although this sounds like it might be a good thing, it’s just the opposite – these bees may become a source of glyphosate for the hive, which can have negative long-term effects on the colony and continue the cycle of damage.
While it sheds a little light on the impact of glyphosate on honeybees, it also raises many questions. How are glyphosate-exposed bees affected by parasites or pathogens? What effects are produced when glyphosate is combined with pesticides like neonicotinoids? It’s important we continue these studies, but it’s even more important that we use this information to fight for the bees. It’s become painfully obvious that our current methods of agriculture are harming pollinators in unforeseen and unpredictable ways.
Written by Paige Bennett for Fractured Paradigm
Original study: Effects of Sub-Lethal Doses of Glyphosate on Honeybee Navigation