(Photo : Creative Commons/Erik Derr)
Scientists have found two commonly-used pesticides block the ability of honey bees to learn and remember.
Research detailed in two papers published by Nature Communications and the Journal of Experimental Biology says when bees are exposed to the two chemicals, neonicotinoids and coumaphos, particularly in combination, the activity in their brains is lowered significantly.
Neonicotinoids, more commonly used in Europe, controls pests on rapaseed and other crops while the group of chemicals called coumaphos, used more in the U.S., are applied to crops to kill the Varroa mite, a parasite that attacks honey bees.
Research done by the University of Dundee in Scotland showed if the pesticides were applied directly to the brains of the pollinators, they caused a loss of brain activity.
"We found neonicotinoids cause an immediate hyper-activation, so an epileptic type activity. This was proceded by neuronal inactivation, where the brain goes quiet and cannot communicate any more. The same effects occur when we used organophosphates," said research team spokesman Christopher Connolly. "And if we used them together, the effect was additive...the effect was greater when both were present."
Another series of lab experiments carried out by another Scotland-based school, Newcastle University, found that bees exposed to both pesticides together were unable to learn and then remember floral smells associated with a sweet nectar reward ---- an essential skill for survival.
Said Newcastle University researcher Sally Williamson: "It would imply that the bees are able to forage less effectively, they are less able to find and learn and remember and then communicate to their hive mates what the good sources of pollen and nectar are."
Current practices for been toxicity testing involves giving bees an acute dose of a substance and then watching to see if they die.
However, the new findings demonstrate that "because bees do these complex learning tasks, they are very social animals and they have a complex behavioral repertoire, they don't need to be killed outright in order not to be affected."
A company that makes the substances said laboratory-based studies did not always apply to bees in the wild, according to the BBC.
Julian Little, communications and government affairs manager at Bayer Crop Science Limited, which produces some of the pesticides, said the data from of laboratory-based studies should not be automatically applied to what's happening in the wild.
"If you take an insecticide and you give it directly to an insect, I can guarantee that you will have an effect. I am not at all surprised that this is what you will see," he said. "What is really important is seeing what happens in real situations --- in real fields, in real bee colonies, in real bee hives, with real bee keepers."
Another report, issued by the U.K.'s Department for Environment, Food and Rural Affairs, also found no link between bee health and exposure to neonicotinoids.
The government agency carried out a study that looked at bumblebees living on the edges of fields treated with the chemicals.
Honey bees around the world face an uncertain future. Colonies have been hit with a host of diseases and loss of habitat.
In the United States, a mysterious condition known as Colony Collapse Disorder has led to a dramatic drop in the country's honey bee numbers.
Researchers have suspected the two pesticides have been adding to the bees' decline.
The European Commission recently called for a temporary moratorium on the use of neonicotinoids based on a study by the European Food Safety Authority.
However, 14 out of the 27 EU nations, including the U.K. and Germany, have opposed the ban.