permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Honeybees abandoning hives and dying due to insecticide use, research finds
| Environment | theguardian.com
http://www.theguardian.com/environment/2014/may/09/honeybees-dying-insecticide-harvard-study

The mysterious vanishing of honeybees from hives can be directly linked to
insectcide use, according to new research from Harvard
University<http://www.bulletinofinsectology.org/pdfarticles/vol67-2014-125-130lu.pdf>.
The scientists showed that exposure to two neonicotinoids, the world's most
widely used class of insecticide, lead to half the colonies studied dying,
while none of the untreated colonies saw their
bees<http://www.theguardian.com/environment/bees>disappear.

"We demonstrated that neonicotinoids are highly likely to be responsible
for triggering 'colony collapse disorder' in honeybee hives that were
healthy prior to the arrival of winter," said Chensheng Lu, an expert on
environmental exposure biology at Harvard School of Public Health and who
led the work.

The loss of honeybees in many countries in the last decade has caused
widespread concern because about three-quarters of the world's food crops
require pollination. The decline has been linked to loss of habitat,
disease and pesticide use. In December 2013, the European Union banned the
use of three 
neonicotinoids<http://www.theguardian.com/environment/2013/apr/29/bee-harming-pesticides-banned-europe>for
two years.

In the new Harvard study, published in the Bulletin of Insectology, the
scientists studied the health of 18 bee colonies in three locations in
central Massachusetts from October 2012 till April 2013. At each location,
two colonies were treated with realistic doses of imidacloprid, two with
clothianidin, and two were untreated control hives.

"Bees from six of the 12 neonicotinoid-treated colonies had abandoned their
hives and were eventually dead with symptoms resembling CCD," the team
wrote. "However, we observed a complete opposite phenomenon in the control
colonies." Only one control colony was lost, the result of infection by the
parasitic fungus Nosema and in this case the dead bees remained in the hive.

Previously, scientists had suggested that neonicotinoids can lead to CCD by
damaging the immune systems of bees, making them more vulnerable to
parasites and disease. However, the new
research<http://www.theguardian.com/education/research>undermines this
theory by finding that all the colonies had near-identical
levels of pathogen infestation.

"It is striking and perplexing to observe the empty neonicotinoid-treated
colonies because honey bees normally do not abandon their hives during the
winter," the scientists wrote. "This observation may suggest the impairment
of honey bee neurological functions, specifically memory, cognition, or
behaviour, as the results from the chronic sub-lethal neonicotinoid
exposure." Earlier research showed neonicotinoid exposure can damage the
renowned ability of bees to navigate
home<http://www.theguardian.com/environment/2012/mar/29/crop-pesticides-honeybee-decline>
.

The new research follows similar previous work by the same
group<http://www.theguardian.com/environment/damian-carrington-blog/2012/apr/11/bees-pesticides-decline-colony-collapse>and
comparison of the two studies shows that cold winters appear to
exacerbate the effects of neonicotinoids on the bees. In the cold winter of
2010-11, 94% of the insecticide-exposed colonies suffered CCD compared to
50% in the new study.

"Sudden deaths of entire honey bee colonies is a persistent concern in
North America," said Paul de Zylva, Friends of the Earth's senior nature
campaigner. "Comprehensive research into the role
pesticides<http://www.theguardian.com/environment/pesticides>play in
bee decline is urgently required – including how they may compound
other pressures, such as a lack of food and loss of habitat." Lu agreed:
"Future research could help elucidate the biological mechanism that is
responsible for linking sub-lethal neonicotinoid exposures to CCD.
Hopefully we can reverse the continuing trend of honeybee loss."