from Patricia Robinette – 05/29/2007
Possible culprit identified in decline of honeybees
http://www.sunjournal.com/story/214 … ified_in_decline_of_honeybees/
They are among the most sensitive and hardest-working creatures in
nature. Ancient navigators of the air, honeybees are guided between
hive and flower by the angle and direction of the sun. Their internal
clock signals the time of day a particular flower’s nectar is
flowing. And daily changes in the earth’s magnetic cycle alert those
in the darkened hive to sunrise and sunset.
A mysterious ailment, however, is causing the great pollinators to
lose their way home. The disorder, called "colony collapse," has
resulted in the deaths of millions of honeybees worldwide and up to
half of the 2.5 million colonies in the United States.
The chief suspect, say many scientists, is the most commonly used
insecticide on the planet: imidacloprid.
"I grew up in the 1960s, and this reminds me of Rachel Carson’s
"Silent Spring,"’ says Douglas Fisher, a New Jersey state legislator,
referring to the 1962 book that warned the world about the long-term
effects of agricultural chemicals on the environment.
Last week Fisher escorted New Jersey’s secretary of agriculture,
Charles M. Kuperus, to some hard-hit beekeeping operations in the
legislator’s Salem County district.
Launched in 1994 by Bayer, the German health care and chemical
company, imidacloprid is used to combat insects such as aphids that
attack more than 140 crops, including fruits and vegetables, cotton,
alfalfa and hops. Sold under various brand names, such as Admire,
Advantage, Gaucho, Merit, Premise and Provado, imidacloprid also is
manufactured for use on flowers, lawns, trees, golf courses and even
pets in the form of flea collars. The list soon could grow even
longer. Last fall, Bayer announced findings indicating imidacloprid’s
ability to promote plant health even in the absence of infestation.
But while it is a successful insecticide, the chemical, in sublethal
doses, may be wreaking havoc on honeybees’ nervous systems. In the
mid-1990s, imidacloprid was implicated in a massive bee die-off in
France, in which a third of the country’s 1.5 million registered
hives were lost. After beekeepers protested, imidacloprid was banned
for several uses, including treatment of sunflowers and corn seed. At
the same time, beekeepers in Germany, Poland, Spain and Switzerland
were suffering similar losses.
"These things (imidacloprid insecticides) do a great job on termites,
fleas, ticks, but people forget honeybees are insects, too," said
Jerry Hayes, president of the Apirary Inspectors of America and an
entomologist with the Florida Department of Agriculture. "It amazes
me the disconnect that chemical companies have – or are allowed to
have – in terms of the effects (of pesticides) on good insects."
Honeybees come into contact with pesticides because insects are
needed to pollinate scores of crops, such as apples, blueberries,
cantaloupes, cranberries, cucumbers, pumpkins and watermelons.
Imidcacloprid is one of the newer chemicals especially effective
against a wide range of pests. A member of a class of pesticides
called neonicotinoids, it is a synthetic derivative of nicotine and
works by impairing the central nervous system of insects, causing
their neurons to fire uncontrollably and eventually leading to muscle
paralysis and death.
The potent chemical can be sprayed on plants, or coated on seeds,
which then release the insecticide through the plants as they grow.
In sublethal doses, however, research has shown that imidacloprid and
other neonicotinoids, such as fipronil, can impair honeybees’ memory
and learning, as well as their motor activity and navigation. When
foraging for food and collecting nectar, honeybees memorize the
smells of flowers and create a kind of olfactory map for subsequent
trips.
However, in laboratory and field studies, honeybees exposed to
imidacloprid seem to wander off, which may explain, say scientists,
why hives all over the world are turning up empty.
Recent studies have reported on the "anomalous flying behavior" of
imidacloprid-treated bees where the workaholic insects simply fall to
the grass or appear unable to fly toward the hive.
In 2003, a French television documentary team filmed honeybee
activity after exposure to imidacloprid. Clumsy and uncoordinated,
their legs trembling, the bees looked like drunks unable to find the
key to the front door of their hive. Others had trouble leaving the
hive, seemed disoriented, and when they were eventually able to make
their way out, soon disappeared, never to return.
The possibility that neonicotinoids are at the heart of the bee die-
off implies a far more complex problem because of the widespread use
of pesticides. Every year these chemicals are applied to hundreds of
millions of acres of agricultural lands, gardens, golf courses and
public and private lawns across the United States. Their use on major
crops nearly tripled between 1964 and 1982, from 233 million pounds
to 612 million pounds of active ingredients. And since then, their
use has exploded. By 1999, the U.S. Environmental Protection Agency
reported 5 billion pounds of pesticides used on U.S. crops, forests,
lawns, flowers, homes and buildings.
Because of imidacloprid’s emergence as a primary player in pest
management, a painful paradox has developed in relation to the recent
debate. Neonicotinoids are needed by farmers and growers to maintain
the health of crops, many of which also require pollination by
honeybees.
"Neonicotinoids are now the best aphid insecticide we have," said
Peter Shearer, a specialist in fruit tree entomology with the Rutgers
Agricultural and Extension Center in Bridgeton, N.J. "It’s very
important to our pests that have shown resistance to other chemicals.
It’s very important to eggplants, potatoes, tomatoes."
Shearer notes that apple farmers, for instance, don’t use Provado,
which has imidacloprid as an active ingredient, until after the bees,
which are used for pollination, are removed from the orchards.
"So it doesn’t seem to be a logical route of bee die-off," he said.
"It would have to last 11 months."
However, Shearer also acknowledges that some published studies
indicate that imidacloprid can persist on both vegetation and in the
soil for weeks, months and perhaps years.
In France, there have been inconsistent results since the bans on
imidacloprid went into effect. In 2005, for the first time in a dozen
years, the French honey harvest improved, but only in certain
regions, according to the country´s beekeeping federation.
Some U.S. entomologists, who recently have been analyzing dead bees,
have found a remarkably high number of viruses and fungal diseases in
the carcasses, leading them to suspect there may be other culprits
besides neonicotinoids.
A 2004 University of North Carolina study, for instance, found that
some neonicotinoids, in combination with certain fungicides,
increased the toxicity of the "neonics" to honeybees a thousand-fold.
"I don’t think there is one smoking gun," said Hayes. "When
neonicotinoids are used on termites, they can’t remember how to get
home, they stop eating and then the fungus takes over and kills them.
That’s one of the ways imidacloprid works on termites – it makes them
vulnerable to other natural organisms. So if you look at what’s
happening to honeybees, that’s pretty scary."
Last week the five-state Mid-Atlantic Apiculture Research and
Extension Consortium released a progress report on colony collapse
disorder. Its findings included "the high prevalence of fungi in
adult bees" which seemed "indicative of stress or a compromised
immune system; these symptoms have never been previously reported."
Another entomologist at the Rutgers center, Gerald Ghidiu, knows
there is no simple answer to the problem.
"They’ve been looking at this since the late 1990s," said the
vegetable specialist. "They’ve done quite a few studies and they
still can’t find the direct link. Seventy-five percent of the
vegetable crops in Arizona gets imidacloprid, but they have no
problems with the honeybees right now. So why isn’t it straight
across the board? Everyone is in the dark over this."
(Mike C comments: What explains the sudden colony collapse this spring, if this insecticide has been in use for years?