Are bees 'hooked' on nectar containing pesticides?

Previous studies have suggested that exposure of this kind can affect bees' fitness. The research, published in Nature, discovered that buff-tailed bumblebees and honeybees could not taste the three most commonly used neonicotinoid pesticides and so did not avoid them. In fact, the bees showed a preference for food which contained pesticides: when the bees were given a choice between sugar solution, and sugar solution containing neonicotinoids, they chose the neonicotinoid-laced food.

The lab-based study also showed that the bumblebees ate more of the food containing pesticides than the honeybees, and so were exposed to higher doses of toxins.

Bees and other pollinating insects are important for increasing crop yields -- their value has been estimated to be worth at least €153billion per year globally. When pollinating crops, they can be exposed to pesticides in floral nectar and pollen. Several controversial studies have shown that neonicotinoids have negative effects on bee foraging and colony fitness. As a result, public concern has grown over the impact of neonicotinoids on bees and other pollinators. In April 2013, the EU introduced a temporary ban on the use of neonicotinoid pesticides on flowering crops, while further scientific and technical evidence was gathered.

Professor Geraldine Wright, lead scientist on the study at the Institute of Neuroscience at Newcastle University, said: "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.

"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. The fact that bees show a preference for food containing neonicotinoids is concerning as it suggests that like nicotine, neonicotinoids may act like a drug to make foods containing these substances more rewarding. "If foraging bees prefer to collect nectar containing neonicotinoids, this could have a knock-on negative impact on whole colonies and on bee populations."

Jane Stout, Professor of Botany and Principal Investigator in the School of Natural Sciences at Trinity College Dublin, said: "Our findings imply that even if alternative food sources are provided for bees in agricultural landscapes where neonicotinoid pesticides are used, the bees may prefer to forage on the neonicotinoid-contaminated crops. Since neonicotinoids can also end up in wild plants growing adjacent to crops, they could be much more prevalent in bees' diets than previously thought."

The study is part of the Insect Pollinators Initiative, jointly funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Defra, the Natural Environment Research Council (NERC), the Scottish Government and the Wellcome Trust under the auspices of the Living with Environmental Change (LWEC) partnership. It was also funded by Science Foundation Ireland, the Irish Research Council, and National Science Foundation.