Many fruit, nut and berry crops depend on honey bees for pollination,
but more and more bee colonies are dying each year. Parasitic mites,
viruses, and pesticides may all play a role, but as Véronique LaCapra
reports, researchers are still looking for a way to stop the die-off.
bees are the most valuable pollinators of agricultural crops worldwide.
In the United States, approximately 130 crops depend on honey bees for
pollination. Their work is worth about $15 billion a year.
VanEnglesdorp is Pennsylvania's acting state apiarist. He's responsible
for tracking the health of the state's commercial honey bee colonies,
and he estimates that one in every three bites of food we eat are
directly or indirectly pollinated by honeybees. "Honeybees are the
moveable pollination force in modern agriculture."
blueberries, and apples; carrots, onions, and squash – all of these
fruits and vegetables grow in different parts of the country and bloom
at different times of the year. So, to meet the pollination demand,
commercial beekeepers truck their hives around the country. A single
beekeeper may move tens of millions of bees, covering thousands of
kilometers in a single trip.
"So all your fruits and vegetables,
all your flowering plants require insect pollination," says
VanEnglesdorp, "and honey bees do a majority of that pollination."
the 1940s and '50s, there were approximately five million managed bee
colonies in the United States. Today, that number has dropped to less
than half that. Severe declines began in the 1980s, with the accidental
introduction of a new parasite called the varroa mite.
actually an amazingly large parasite," describes VanEnglesdorp. "If we
were a bee, it would be like a dinner plate feeding on us." The mite
has very sharp mouthparts, which it uses to pierce the skin – or
exoskeleton – of the bee. Van Englesdorp says that varroa actually
spits inside the bee, "and in that spit we believe that there's a
protein which acts a lot like AIDS virus does in the fact that it
breaks down the insect's immune system."
The mite can also
transmit viruses and other pathogens from bee to bee, and wipe out
entire colonies. According to VanEnglesdorp, varroa is the biggest
challenge facing commercial beekeepers: "it still kills most of the
colonies in the country."
Jeff Pettis is the lead scientist at
the U.S. Department of Agriculture's Bee Research Lab, just outside of
Washington, D.C. Pettis and his team have been studying a more recent
and mysterious threat to honey bee colonies. Honeybee colonies usually
suffer a loss of about 15 to 20 percent each year. "Our last two years
we've been over 30 percent losses," says Pettis, "and so this is what
we're calling this phenomenon of CCD, colony collapse disorder."
looks very different from other causes of bee death, and it happens
much more quickly: within just a few weeks, most of the adult worker
bees disappear from the hive, leaving the queen and all the young bees
Since CCD was first reported, researchers have been
scrambling to find a cause. They've looked at parasites, viruses,
pesticides, and even colony management problems like poor nutrition and
Pettis says that researchers
have already done enough testing that if one new pathogen or other
problem were causing the bee deaths, they would already have identified
it. "We think it's a complex, maybe even a syndrome – things that are
coming together to cause the losses of bees."
The lack of clear
answers worries Dennis VanEnglesdorp. "What's really frightening about
this new condition is we don't know what causes it, so we don't know
how to stop it." He says that the mobile, commercial honeybee
operations that we rely on to pollinate different crops across the
country are in real danger. In a single year, "they can lose 30 to 50,
sometimes 80 percent of their colonies." Van Englesdorp says beekeepers
can absorb that kind of loss for a year or two, "but they can't do it
three years in a row and stay in business."
And bee declines are
not limited to the United States. "We're hearing reports from Europe,
from Canada, and from South America, even some from Asia – where
honeybee populations are collapsing and decreasing."
still enough bees in the U.S. to meet demand, but VanEnglesdorp warns
that continued colony losses could threaten the production of some
crops, and drive more and more beekeepers out of business.