Bees May Become "Addicted" To Pesticides, Study Claims

By Paul Gaita 09/07/18

The possibility for an addictive response underscores the concern over global use of the controversial insecticide.

bumblebee on a flower

Researchers in London have found that bumblebees may develop a preference for food that is laced with pesticide that can echo the addictive effects of nicotine on humans.

The study looked at a class of pesticide from the neonicotinoid family, a controversial form of insecticide used in farming that some scientists have claimed can be harmful to bees. When offered options for food—one with the pesticide and one without—bees initially preferred the latter, but upon consuming the chemically-treated food, they returned to it with greater frequency.

The possibility for an addictive response underscores concern over global use of neonicotinoids, which were banned by the European Union in 2018.

The study, conducted by researchers from London's Imperial College and Queen Mary University, was intended to reproduce real foraging behavior by bumblebees, including social cues used in that activity.

To determine if the introduction of neonicotinoids into the bees' food sources, 10 colonies of bees were introduced to several sucrose feeders, each containing a solution with varying degrees (in parts per billion) of a neonicotinoid called thiamethoxam.

Over a period of 10 days, the researchers found that bees initially preferred what IFL Science called the "pure" solution, which contained no pesticide. But once a bee consumed a solution that contained thiamethoxam, it would return to that solution more regularly and avoid the pure solution. Changing the position of the feeders also appeared to have no impact on the bees' preference for the pesticide-laced solution.

The researchers' comparison between the bees' reaction to the neonicotinoid and human response to nicotine is not accidental: as study lead author Richard Gill noted in a statement: "neonicotinoids" target nerve receptors in insects that are similar to receptors targeted by nicotine in mammals."

As Texas A&M's AgriLife Extension Service posted on its site, the term "neonicotinoid" is translated literally as "new nicotine-like insecticide."

Though agriculturalists and scientists are split on how neonicotinoids affect bees, they cause paralysis and eventual death in the bugs they are intended to repel, such as aphids or root-feeding grubs. Unlike contact pesticides, they are absorbed by the plant and transported through its system, and will remain in the plant for many weeks. 

And while studies have shown that the pesticide class is less harmful to birds and mammals, others have suggested that it can affect a variety of crucial foraging skills for bees, including motor functions and navigation.

Some have even linked the increase in the population of bees in the city over those located in rural areas to the use of such pesticides. The potential for harm to bees is among the key reasons why the European Union chose to ban the use of neonicotinoids in agriculture, save for permanent greenhouses, in 2018.

However, in his statement, Gill wrote, "Whilst neonicotinoids are controversial, if the effects of replacements on non-target insects are not understood, then I believe it is sensible that we take advantage of current knowledge and further studies to provide guidance for using neonicotinoids more responsibly, rather than necessarily an outright ban."

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, and The Los Angeles Beat, among many other publications and websites.