Excellent article in the Los Angeles Times about bees

The puzzling phenomenon, known as Colony Collapse Disorder, or CCD, has been reported in 35 states, five Canadian provinces and several European countries. The die-off has cost U.S. beekeepers about $150 million in losses and an uncertain amount for farmers scrambling to find bees to pollinate their crops.

Scientists have scoured the country, finding eerily abandoned hives in which the bees seem to have simply left their honey and broods of baby bees.

"We've never experienced bees going off and leaving brood behind," said Pennsylvania-based beekeeper Dave Hackenberg. "It was like a mother going off and leaving her kids."

Researchers have picked through the abandoned hives, dissected thousands of bees, and tested for viruses, bacteria, pesticides and mites.

So far, they are stumped.

According to the Apiary Inspectors of America, 24% of 384 beekeeping operations across the country lost more than 50% of their colonies from September to March. Some have lost 90%.

"I'm worried about the bees," said Dan Boyer, 52, owner of Ridgetop Orchards in Fishertown, Pa., which grows apples. "The more I learn about it, the more I think it is a national tragedy."

At Boyer's orchard, 400 acres of apple trees — McIntosh, Honey Crisp, Red Delicious and 11 other varieties — have just begun to bud white flowers.

Boyer's trees need to be pollinated. Incompletely pollinated blooms would still grow apples, he said, but the fruit would be small and misshapen, suitable only for low-profit juice.

This year, he will pay dearly for the precious bees — $13,000 for 200 hives, the same price that 300 hives cost him last year.

The scene is being repeated throughout the country, where honeybees, scientifically known as Apis mellifera, are required to pollinate a third of the nation's food crops, including almonds, cherries, blueberries, pears, strawberries and pumpkins.

[snip]

VanEngelsdorp, 37, quickly eliminated the most obvious suspects: Varroa and tracheal mites, which have occasionally wrought damage on hives since the 1980s.

At the state lab in Harrisburg, Pa., VanEngelsdorp checked bee samples from Pennsylvania and Georgia. He washed bees with soapy water to dislodge Varroa mites and cut the thorax of the bees to look for tracheal mites; he found that the number of mites was not unusually high.

His next guess was amoebic infection. He scanned the bees' kidneys for cysts and found a handful, but not enough to explain the population decline.

VanEngelsdorp dug through scientific literature looking for other mass disappearances.

He found the first reference in a 1869 federal report, detailing a mysterious bee disappearance. There was only speculation as to the cause — possibly poisonous honey or maybe a hot summer.

A 1923 handbook on bee culture noted that a "disappearing disease" went away in a short time without treatment. There was a reference to "fall dwindle" in a 1965 scientific article to describe sudden disappearances in Texas and Louisiana.

He found other references but no explanations.

[snip]

A number of the pollen samples went to Maryann Frazier, a honeybee specialist at Penn State who has been coordinating the pesticide investigation. Her group has been testing for 106 chemicals used to kill mites, funguses or other pests.

Scientists have focused on a new group of pesticides known as neonicotinoids, which have spiked in popularity because they are safe for people, Frazier said. Studies have shown that these pesticides can kill bees and throw off their ability to learn and navigate, she said.

Researchers have yet to collect enough data to come to any conclusions, but the experience of French beekeepers casts doubt on the theory. France banned the most commonly used neonicotinoid in 1999 after complaints from beekeepers that it was killing their colonies. French hives, however, are doing no better now, experts said.

[snip]

If the cause is not a poison, it is most likely a parasite.

UC San Francisco researchers announced in April that they had found a single-celled protozoan called Nosema ceranae in bees from colonies with the collapse disorder.

Unfortunately, Bromenshenk said, "we see equal levels of Nosema in CCD colonies and healthy colonies."

[snip]

Several researchers, including entomologist Diana Cox-Foster of Penn State and Dr. W. Ian Lipkin, a virologist at Columbia University, have been sifting through bees that have been ground up, looking for viruses and bacteria.

"We were shocked by the huge number of pathogens present in each adult bee," Cox-Foster said at a recent meeting of bee researchers convened by the U.S. Department of Agriculture.

The large number of pathogens suggested, she said, that the bees' immune systems had been suppressed, allowing the proliferation of infections.

The idea that a pathogen is involved is supported by recent experiments conducted by VanEngelsdorp and USDA entomologist Jeffrey S. Pettis.

One of the unusual features of the disorder is that the predators of abandoned beehives, such as hive beetles and wax moths, refuse to venture into infected hives for weeks or longer.

"It's as if there is something repellent or toxic about the colony," said Hayes, the Florida inspector.

[snip]

In the absence of knowledge, theories have proliferated, including one that Osama bin Laden has engineered the die-off to disrupt American agriculture.

One of the most pervasive theories is that cellphone transmissions are causing the disappearances — an idea that originated with a recent German study. Berenbaum called the theory "a complete figment of the imagination."

The German physicist who conducted the tiny study "disclaimed the connection to cellphones," she said. "What they put in the colony was a cordless phone. Whoever translated the story didn't know the difference."

Update June 16: University of Montana has an up-to-date Honey Bee CCD page.