Scientists found that pesticides were
affecting honey bees ability to learn and remember
Commonly used
pesticides are damaging honey bee brains, studies suggest.
Scientists have found that two types of chemicals called
neonicotinoids and coumaphos are interfering with the insect's
ability to learn and remember.
Experiments revealed that exposure was also lowering brain
activity, especially when the two pesticides were used in
combination.
The research is detailed in two papers in
Nature Communications
and the
Journal of Experimental Biology.
But a company that makes the substances said laboratory-based
studies did not always apply to bees in the wild.
And
another report, published by the Defra's Food and Environment
Research Agency (Fera), concluded that there was no link between bee
health and exposure to neonicotinoids.
The government agency carried out a study looking at bumblebees
living on the edges of fields treated with the chemicals.
Falling numbers
Honey bees around the world are facing an uncertain future.
They have been hit with a host of diseases, losses of habitat,
and in the US the mysterious Colony Collapse Disorder has caused
numbers to plummet.
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“Start Quote
It would imply that the bees are able
to forage less effectively”
Dr Sally Williamson
Newcastle University
Now researchers are asking whether
pesticides are also playing a role in their decline.
To investigate, scientists looked at two common pesticides:
neonicotinoids, which are used to control pests on oil seed rape and
other crops, and a group of organophosphate chemicals called
coumaphos, which are used to kill the Varroa mite, a parasite that
attacks the honey bee.
Neonicotinoids are used more commonly in Europe, while coumaphos
are more often employed in the United States.
Work carried out by the University of Dundee, in Scotland,
revealed that if the pesticides were applied directly to the brains
of the pollinators, they caused a loss of brain activity.
Dr Christopher Connolly said: "We found neonicotinoids cause an
immediate hyper-activation - so an epileptic type activity - this
was proceeded by neuronal inactivation, where the brain goes quiet
and cannot communicate any more. The same effects occur when we used
organophosphates.
"And if we used them together, the effect was additive, so they
added to the toxicity: the effect was greater when both were
present."
Another series of laboratory-based experiments, carried out at
Newcastle University, examined the behaviour of the bees.
The researchers there found that bees exposed to both pesticides
were unable to learn and then remember floral smells associated with
a sweet nectar reward - a skill that is essential for bees in search
of food.
Dr Sally Williamson said: "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."
'No threat'
She said that companies that are
manufacturing the pesticides should take these findings into account
when considering the safety of the chemicals.
Decisions on the use
of neonicotinoids must be based on sound scientific
evidence”
Ian Boyd
Defra
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She explained: "At the moment, the initial
tests for bee toxicity are giving the bees an acute dose and then
watching them to see if they die.
"But because bees do these complex learning tasks, they are very
social animals and they have a complex behavioural repertoire, they
don't need to be killed outright in order not to be affected."
The European Commission recently called for a temporary
moratorium on the use of neonicotinoids after a report by the
European Food Safety Authority concluded that they posed a high
acute risk to pollinators.
But 14 out of the 27 EU nations - including the UK and Germany -
opposed the ban, and the proposal has now been delayed.
Ian Boyd, chief scientist at Defra, said: "Decisions on the use
of neonicotinoids must be based on sound scientific evidence."
He said that the results of the Fera bumblebee study suggested
that the extent of the impact might not be as high as some studies
had suggested - and called for "further data based on more realistic
field trials is required".
Dr Julian Little, communications and government affairs manager
at Bayer Crop Science Limited, which makes some of the pesticides,
said the findings of laboratory-based studies should not be
automatically extrapolated to the field.
"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 explained.
"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."