A fungus that hit hives in Europe and Asia may be partly to blame for wiping out colonies across the U.S.
By Jia-Rui Chong and Thomas H. Maugh II
Times Staff Writers
April 26, 2007
A fungus that caused widespread loss of bee colonies in Europe and Asia may be
playing a crucial role in the mysterious phenomenon known as Colony Collapse
Disorder that is wiping out bees across the United States, UC San Francisco
researchers said Wednesday.
Researchers have been struggling for months to explain the disorder, and the
new findings provide the first solid evidence pointing to a potential cause.
But the results are "highly preliminary" and are from only a few hives from Le
Grand in Merced County, UCSF biochemist Joe DeRisi said. "We don't want to
give anybody the impression that this thing has been solved."
Other researchers said Wednesday that they too had found the fungus, a
single-celled parasite called Nosema ceranae, in affected hives from
around the country — as well as in some hives where bees had survived. Those
researchers have also found two other fungi and half a dozen viruses in the
dead bees.
N. ceranae is "one of many pathogens" in the bees, said entomologist
Diana Cox-Foster of Pennsylvania State University. "By itself, it is probably
not the culprit … but it may be one of the key players."
Cox-Foster was one of the organizers of a meeting in Washington, D.C., on
Monday and Tuesday where about 60 bee researchers gathered to discuss Colony
Collapse Disorder.
"We still haven't ruled out other factors, such as pesticides or inadequate
food resources following a drought," she said. "There are lots of stresses
that these bees are experiencing," and it may be a combination of factors that
is responsible.
Historically, bee losses are not unusual. Weather, pesticide exposures and
infestations by pests, such as the Varroa mite, have wiped out significant
numbers of colonies in the past, particularly in the 1960s and 1970s.
But the current loss appears unprecedented. Beekeepers in 28 states, Canada
and Britain have reported large losses. About a quarter of the estimated 2.4
million commercial colonies across the United States have been lost since
fall, said Jerry Hayes of the Florida Department of Agriculture and Consumer
Services in Gainesville.
"These are remarkable and dramatic losses," said Hayes, who is also president
of the Apiary Inspectors of America.
Besides producing honey, commercial beehives are used to pollinate a third of
the country's agricultural crops, including apples, peaches, pears,
nectarines, cherries, strawberries and pumpkins. Ninety percent of
California's almond crop is dependent on bees, and a loss of commercial hives
could be devastating.
"For the most part, they just disappeared," said Florida beekeeper Dave
Hackenberg, who was among the first to note the losses. "The boxes were full
of honey. That was the mysterious thing. Usually other bees will rob those
hives out. But nothing had happened."
Researchers now think the foraging bees are too weak to return to their hives.
DeRisi and UCSF's Don Ganem, who normally look for the causes of human
diseases, were brought into the bee search by virologist Evan W. Skowronski of
the U.S. Army's Edgewood Chemical Biological Center in Maryland.
Dr. Charles Wick of the center had used a new system of genetic analysis to
identify pathogens in ground-up bee samples from California. He found several
viruses, including members of a recently identified genus called iflaviruses.
It is not known whether these small, RNA-containing viruses, which infect the
Varroa mite, are pathogenic to bees.
Skowronski forwarded the samples to DeRisi, who also found evidence of the
viruses, along with genetic material from N. ceranae.
"There was a lot of stuff from Nosema, about 25% of the total,"
Skowronski said. "That meant there was more than there was bee RNA. That leads
me to believe that the bee died from that particular pathogen."
If N. ceranae does play a role in Colony Collapse Disorder, there may
be some hope for beekeepers.
A closely related parasite called Nosema apis, which also affects bees,
can be controlled by the antibiotic fumagillin, and there is some evidence
that it will work on N. ceranae as well.
http://www.latimes.com/news/science/la-sci-bees26apr26%2C0%2C896792.story?coll=la-home-headlines
