The recent Trump administration’s rescinding of the ban on the use of bee-harming pesticides – neonicotinoids – in wildlife refuges was met with understandable derision. Back when the European Union (EU) voted to ban the use of neonicotinoids, however, it was pointed out that by not using them, we’d be opening ourselves up to a rather complex issue: What pesticides should we be using instead?
Crops need to be protected from pests, and pesticides are good at that, but are they harmless to bees? A new Nature study, led by Royal Holloway University of London researchers, finds evidence that a group of pesticides certainly don’t seem to be.
These are insecticides based on sulfoximines, a huge family of chemical compounds that have a range of uses. They are relatively new to the insecticide world, with a 2013 paper describing them as being highly effective against neonicotinoid-resistant insects, particularly sap-feeding critters.
They’ve recently been proposed by legislators and industry experts as a clear alternative to those bee-harming compounds. Already, one sulfoximines-based insecticide – Sufoxaflor – is permitted to be used in 47 countries around the world, including the US and within the EU.
As it happens, the biochemistry behind their repellent nature is still being ascertained, which is why the more we know about it, the better we will understand any accidental, unintended effects they may have.
This new study finds that doses of the aforementioned insecticide equivalent to those used in a real agricultural field have negative, if not lethal, effects on Bombus terrestris, or bumblebee, colonies. Specifically, it renders them less capable of reproduction and appears to render them less healthy in general.
The experiment itself was fairly elegant and simple: field-based bumblebee colonies were either exposed or not exposed to various doses of the insecticides during their initial growth phases, and those that were produced significantly fewer worker bees and gynes, female bees destined to become queens. Ultimately, this led to a 54 percent reduction in the number of sexual offspring produced compared to the control colonies.
In fact, the effects were seen rather quickly, just 9 weeks post-exposure, suggesting that long-term consequences can be set into motion very early on.
Again, the bees aren’t directly killed by the use of the compound, but something as of yet unknown appears to render them less populous a colony over time. “Our results caution against the use of sulfoximines as a direct replacement for neonicotinoids,” the team conclude.
Evidence pointing to the harm caused by neonicotinoids is pretty substantial by this point, which is why the EU – and the Obama administration – banned them. This is the first paper indicating that one sulfoximine-based insecticide can harm bumblebee colonies. Don’t expect the story to end here.