Neonicotinoid Pesticides Impair Bees' Social Behavior, New Study Shows

A study from Harvard University has shown that exposure to pesticides hinders bees' ability to nurse larvae and insulate their colonies.
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Neonicotinoid Pesticides Impair Bees' Social Behavior, New Study Shows

A new Harvard study has shown that exposure to neonicotinoid pesticides has “profound effects” on the social behavior of bees, according to a news release.

The study, led by James Crall at the Thomas D. Cabot Associate Professor of Organismic and Evolutionary Biology, shows that bees exposed to the pesticide spend less time nursing larvae and are less social than other bees.

The study also shows that pesticide exposure impairs bees’ ability to insulate their nests and their colonies.

"This work—especially on thermoregulation—opens up a new set of questions, not just about what the direct effects of pesticides are, but how those pesticides impair the ability of colonies to cope with other stressors," Crall says in the news release. "This work suggests that, in particularly extreme environments, we might expect the effects of pesticides to be worse, so it changes both how we go about practically testing agro-chemicals in general, but it points to specific questions about whether we might see stronger declines in certain environments."

Several studies have already shown that neonicotinoids impair bees’ ability to navigate, forage, and communicate, including studies commissioned by Syngenta and Bayer, two of the world's leading agrochemical companies, and made public via Freedom of Information Act requests. Crall notes, however, that despite this mounting evidence supporting the theory that neonics are dangerous for bees, “there were reasons to suspect that wasn't the whole picture."

"Foraging is only a part of what bumblebees do," Crall says. "Those studies were picking up on the important effects these compounds were having on what's going on outside the nest, but there's a whole world of really important behaviors going on inside...and that's a black box we wanted to open up a bit."

The study was conducted by using QR codes to track each individual bee in a many as a dozen colonies at a time, allowing the researchers to see behaviors happening within the hive.

Crall notes that this and other research on this topic should point to mounting concern about the ways that climate change is "undercutting and decimating insect populations," not only with regards to natural ecosystems but also with regards to food production.

"Our food system is becoming more and more pollinator-dependent over time—today about a third of food crops are dependent on pollinators, and that's only rising," he says. "Up until now, we've had this abundant, natural gift of pollinators doing all this work for us, and now we're starting to realize that isn't a given, so I think we should be very worried about that."

Growing research linking neonicotinoid pesticides to issues such as bee death led the European Union to ban the three most commonly used substances in this class earlier this year.

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