Pesticides have long been linked to the decline of bee populations around the world. While there are many possible causes for bees dying off, ranging from parasites to reduced food sources, the most insidious and difficult to ascertain factor has been pesticides. However, a recent study has shed light on a controversial group of pesticides, called neonicotinoids, which may get bees addicted to harmful chemicals in the same way that nicotine causes addiction in smokers.
Currently, the use of three of these neonicotinoid pesticides is banned by the European Union. Neonicotinoids are often applied to seeds, and, as the Telegraph reported on April 22, are chemically similar to nicotine in that they are toxic to insects at high doses but potentially addictive in small quantities. In fact, the tobacco plant uses nicotine to protect itself from plant eating insects. Although the U.S. does not have any restrictions on this class of pesticides, the U.S. Environmental Protection Agency has said that it will likely refrain from approving any new versions of the neonicotinoid pesticides until more research has been done on the effects the chemicals have on bees.
According to the journal Nature, which published two studies on the effects of neonicotinoids on bees, many of the critics of research into the controversial chemicals claim that if the chemicals were truly harmful to bees, the insects would stay away from the pesticides in the first place. This claim was put to the test by Professor Geraldine Wright, of the Institute of Neuroscience at the University of Newcastle.
“Bees can’t taste neonicotinoids in their food and therefore do not avoid these pesticides. This is putting them at risk of poisoning when they eat contaminated nectar,” she told the Telegraph. “Even worse, we now have evidence that bees prefer to eat pesticide-contaminated food. Neonicotinoids target the same mechanisms in the bee brain that are affected by nicotine in the human brain.”
Wright and her team confined both honeybees and bumblebees in a lab and offered them a choice of plain nectar, and nectar spiked with neonicotinoids. The bees chose the nectar treated with the pesticides every time over the plain nectar. Wanting to know if the bees could actually taste the difference between plain sugar water, and the treated stuff, Wright and her team monitored the taste neuron of bees and found that the insects responded exactly the same, regardless of the concentration of neonicotinoids in the solution, suggesting they couldn’t taste the pesticides at all.
“A little bit’s medicine and a lot’s toxin. If you have a high enough dose of the stuff it will kill you. At very low doses, though, like the ones found in cigarettes, it’s got a pharmacological effect that affects the reward pathway in the human brain. I think what’s happening here is something very analogous,” said Wright. “I don’t think they (the bees) can taste it at all. They’re learning the location of the food that contains it. And during the time that they’re eating it they’re getting a stronger feeling of reward.”
Although Wright says that it is too early to determine whether neonicotinoids are truly addictive to bees, she says that it is a very real possibility. At the moment, Wright said, what is needed is more data, so that we can start making informed decisions about pesticides.