Pesticides Confuse Bees : Study Suggests
Posted by Unknown in Beekeeping, Honey Bee, Pesticide, Research and Studies on Tuesday 14 May 2013
John von Radowitz, PA
Times of Malta
 |
| Insecticides disrupt their learning, threatening survival and reducing pollination |
Commonly used pesticides confuse bees by disrupting the learning circuits in their brains, a study has found.
The effects
could make it harder for bees to forage among flowers for food, thereby
threatening their survival and reducing pollination.
Bees exposed to
two kinds of pesticide were slower to learn or completely forgot
important associations between floral scents and nectar.
The impact of the chemicals increased when they were combined together.
One group of
compounds tested were neonicotinoids, which are related to nicotine and
used around the world to control a variety of pests. The other
pesticide, coumaphos, is employed outside the EU to kill the Varroa mite
that attacks honeybees.
In the laboratory, scientists exposed bees’ brains to levels of the pesticides similar to those found in the wild.
They then
recorded electrical activity from cells from a higher order bee brain
structure called the ‘mushroom body’ which is important for memory and
learning. Forty per cent of a bees’ neurons can be found in the mushroom
bodies.
The results showed that both chemicals targeted this region of the bee brain, causing a loss of function.
Other research
by collaborating scientists showed that up to 30 per cent of honeybees
exposed to combinations of the pesticides for four days failed to learn
and performed poorly in memory tests.
The findings are published in the journal Nature Communications.
Geraldine
Wright, from the University of Newcastle, said: “Pollinators perform
sophisticated behaviours while foraging that require them to learn and
remember floral traits associated with food. Disruption in this
important function has profound implications for honeybee colony
survival, because bees that cannot learn will not be able to find food.”
Christopher
Connelly, whose team at the University of Dundee conducted the brain
recordings, said: “Much discussion of the risks posed by the
neonicotinoid insecticides has raised important questions of their
suitability for use in our environment.
However, little
consideration has been given to the miticidal pesticides introduced
directly into honeybee hives to protect the bees from the Varroa mite.
We find that both have negative impact on honeybee brain function.
“Together,
these studies highlight potential dangers to pollinators of continued
exposure to pesticides that target the insect nervous system and the
importance of identifying combinations of pesticides that could
profoundly impact pollinator survival.”
Bee expert
Francis Ratnieks, professor of apiculture at the University of Sussex,
said: “Bees are wonderful creatures in their own right, and are of
increasing importance to our own food supply through pollination. This
makes it extremely important that we understand what affects their
health and causes declines in their populations.
“It’s no
surprise that insecticides at high concentrations are harmful, but we
don’t know whether the low levels of neonicotinoid insecticides in the
nectar and pollen of treated plants, such as oil seed rape, are harmful
in the real world.
“This new
research gives us basic knowledge of how these insecticides affect
specific cells in the honeybee brain that play a role in honeybee
learning and behaviour.”
Reduced numbers
of flowers and wildlife habitats due to the intensification of farming
was probably the most important factor behind bee loss.
Ratnieks added that coumaphos could not legally be used to control Varroa mites in the UK and EU.
