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 in a first-of-its-kind
study
published today in the journal PLOS ONE,
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 vanEngelsdorp, 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 vanEngelsdorp,
an assistant research scientist at the University of Maryland, 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: US honey bees,
which are descendants of European bees, do not bring home pollen from
native North American crops but collect bee chow from nearby weeds and
wildflowers. That pollen, however, 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
vanEngelsdorp.
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