A Deadly Cocktail

A new study published last month, addressing bumble bees, is showing that fungicides are in fact very bad for them, indicating the same for honey bees.  Fungicides previously considered relatively harmless to honey bees, have a synergistic relationship with insecticides, and it is this connection that is creating a deadly cocktail.

Co-author of the study, Scott McArt said that ‘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’.

According to an article in Catch the Buzz, by “building on a large data set collected by Sydney Cameron, professor of entomology at the University of Illinois, the scientists discovered what they call “landscape-scale” connections between fungicide usage, pathogen prevalence and declines of endangered United States bumblebees. (Landscape scale refers to the area in which foraging bumblebees live, about 2 kilometers in diameter.) While fungicides control plant pathogens in crops, the bees pick up their residue when foraging for pollen and nectar. 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. Chlorothalonil has been linked to stunted colony growth in bumblebees and an increased vulnerability to Nosema, a fatal gut infection in bumblebees and honeybees.”

“Nosema can be devastating to bumblebees and honeybees,” said McArt. “Since fungicide exposure can increase susceptibility of bees to Nosema, this may be the reason we’re seeing links between fungicide exposure, Nosema prevalence and bumblebee declines across the United States in this data set.”

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