When a Cornell-led team of scientists analyzed two dozen environmental factors to understand bumblebee population declines and range contractions, they expected to find stressors like changes in land use, geography or insecticides.
Instead, they found a shocker: fungicides, commonly thought to have no impact.
"Insecticides work; they kill insects. Fungicides have been largely overlooked because they are not targeted for insects, but fungicides may not be quite as benign - toward bumblebees - as we once thought. This surprised us," said Scott McArt, assistant professor of entomology and the lead author on a new study published Nov. 15 in the journal Proceedings of the Royal Society B.
While science has studied insecticides, such as neonicotinoids, that attack bugs' central nervous systems, this new work shows how fungicides - particularly chlorothalonil, a general-use fungicide often found in bumblebee and honeybee hives - may negatively affect bee health, said McArt....
[T]he scientists discovered what they call "landscape-scale" connections between fungicide usage, pathogen prevalence and declines of endangered United States bumblebees.
As farms use both insecticides and fungicides, the scientists worry about synergy. "While most fungicides are relatively nontoxic to bees, many are known to interact synergistically with insecticides, greatly increasing their toxicity to the bees," McArt said.
[Editor's note: Read the full study (behind paywall)]
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