The UK government has announced that whilst it accepts the European Union ban on neonicotinoid pesticides, it does not believe that there is enough scientific evidence to support this action.
In April, the EU banned the use of neonicotinoid pesticides for two years starting in
December because of concerns over their effect on bees. The
use of these pesticides will not be allowed on flowering crops that attract
bees or by the general public, however winter crops may still be treated.
Fifteen countries voted for this ban, with eight voting against it (including
the UK and Germany) and four countries abstaining.
Neonicotinoids were originally thought to have less of an
impact on the environment and human health than other leading pesticides. They
are systemic insecticides, which means they are transported throughout the
plant in the vascular system making all tissues toxic to herbivorous insects
looking for an easy meal. The most common application in the UK is to treat
seeds before they are sown to ensure that even tiny seedlings are protected
against pests.
 |
| Image by Kath Baldock |
The major concern over neonicotinoids is whether nectar
and pollen contains levels of pesticide is high enough to cause problems for
bees. It has already been shown that they do not contain a lethal dose, however
this is not the full story. Bees live in complex social colonies and work
together to ensure that there is enough food for developing larvae and the
queen. Since neonicotinoids were introduced in the early 1990s bee populations
have been in decline and there is a growing feeling of unease that the two may
be connected. Scientific research has provided evidence both for and against a
possible link leaving governments, farmers, chemical companies environmentalists
and beekeepers in an endless debate about whether or not a ban would save our
bees.
Several studies on bees have shown that sublethal levels
of neonicotinoids disrupt bee behaviour and memory. These chemicals target
nicotinic acetylcholine receptors, one of the major ways that signals are sent
through the insect central nervous system. Scientists at Newcastle University
recently showed that bees exposed to neonicotinoids were less able to form long-term memories associating a smell with a
reward, an important behaviour when foraging for pollen and nectar in the wild.
Researchers at the University of Stirling fed bumble bee
colonies on pollen and sugar water laced with neonicotinoids for two weeks to
simulate field-like exposure to flowering oil seed rape. When the colonies were
placed into the field, those that had been fed the pesticides grew more slowly
and produced 85% less queens
compared with those fed on untreated pollen and nectar. The
production of new queens is vital for bee survival because they start new
colonies the next year. Studies in other bee species have found that only the
largest colonies produce queens, so if neonicotinoids have even a small effect
on colony size it may have a devastating effect on queen production.
So why does the government argue that there is not enough
scientific evidence to support a ban on neonicotinoids?
 |
| Image by Kath Baldock |
In 2012, the Food and Environment Research Agency set up
a field trial using bumble bee
colonies placed on sites growing either neonicotinoid-treated oil seed rape or
untreated seeds. They found no significant difference between the amount of
queens produced on each site, although the colonies near neonicotinoid-treated
crops grew more slowly. The study also found that the levels of pesticide present
in the crops was much lower than previously reported.
I personally think that both laboratory and field studies
bring important information to the debate, however neither has the full answer.
Whilst more realistic, the government’s field trial suffered from a lack of
replication, variation in flowering times and various alternative food sources
available to bees. Only 35% of pollen collected by the bees was from the oil
seed rape plants, so where oil seed rape comprises the majority of flowering
plants available to bees the effect on neonicotinoids may be more pronounced.
The laboratory research can control more variables to establish a more clear
picture, however the bees in these studies were often given only
neonicotinoid-treated pollen and nectar to eat, which clearly is not the case
in a rural landscape. Flies and beetles have been shown to avoid neonicotinoids, which could mean that bees would
find alternative food sources where possible. This would have a major impact on crop pollination.
We desperately need well-designed field studies looking
at the effect of neonicotinoids on bees and the environment in general. Despite
an EU moratorium on growing neonicotinoid treated crops, an allowance should be
made for scientists to set up controlled field trials to study the effect of
these pesticides on bees during the two year ban. It could be our only chance
to determine the danger these chemicals pose to vital pollinators and the wider
environment.
 |
Sarah Jose
|