July 24, 2013
As we’ve written before,
the mysterious mass die-off of honey bees that pollinate $30 billion worth of
crops in the US has so decimated America’s apis mellifera population
that one bad winter could leave fields fallow. Now, a new study has
pinpointed some of the probable causes of bee deaths and the rather scary results
show that averting beemageddon will be much more difficult than previously
thought.
Scientists had struggled to
find the trigger for so-called Colony Collapse Disorder (CCD) that has wiped
out an estimated 10 million beehives, worth $2 billion, over the past six
years. Suspects have included pesticides, disease-bearing parasites and poor
nutrition. But scientists at the University of Maryland and the US Department
of Agriculture have identified a witch’s brew of pesticides and fungicides
contaminating pollen that bees collect to feed their hives. The findings
break new ground on why large numbers of bees are dying though they do not
identify the specific cause of CCD, where an entire beehive dies at once.
When researchers collected
pollen from hives on the east coast pollinating cranberry, watermelon and other
crops and fed it to healthy bees, those bees showed a significant decline in
their ability to resist infection by a parasite called Nosema ceranae.
The parasite has been implicated in Colony Collapse Disorder though scientists
took pains to point out that their findings do not directly link the pesticides
to CCD. The pollen was contaminated on average with nine different pesticides
and fungicides though scientists discovered 21 agricultural chemicals in one
sample. Scientists identified eight ag chemicals associated with increased risk
of infection by the parasite.
Most disturbing, bees that
ate pollen contaminated with fungicides were three times as likely to be
infected by the parasite. Widely used, fungicides had been thought to be
harmless for bees as they’re designed to kill fungus, not insects, on crops
like apples.
“There’s growing evidence
that fungicides may be affecting the bees on their own and I think what it
highlights is a need to reassess how we label these agricultural chemicals,”
Dennis van Engelsdorp, the study’s lead author, told Quartz.
Labels on pesticides warn
farmers not to spray when pollinating bees are in the vicinity but such
precautions have not applied to fungicides.
Bee populations are so low
in the US that it now takes 60% of the country’s surviving colonies just to
pollinate one California crop, almonds. And that’s not just a west coast
problem—California supplies 80% of the world’s almonds, a market worth $4
billion.
In recent years, a class of
chemicals called neonicotinoids has been linked to bee deaths and in April
regulators banned the use of the pesticide for two years in Europe where bee
populations have also plummeted. But van Engelsdorp says the new study shows
that the interaction of multiple pesticides is affecting bee health.
“The pesticide issue in
itself is much more complex than we have led to be believe,” he says. “It’s a
lot more complicated than just one product, which means of course the solution
does not lie in just banning one class of product.”
The study found another
complication in efforts to save the bees: Pollen from nearby weeds and
wildflowers was also contaminated with pesticides even though those plants were
not the target of spraying.
“It’s not clear whether the
pesticides are drifting over to those plants but we need take a new look at
agricultural spraying practices,” says van Engelsdorp.
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