Not-so-elementary bee mystery: detectives sift clues in the case of the missing insects

Science News, July 28, 2007 by Susan Milius

The disappearance of large numbers of U.S. honeybees is so odd that it's attracted Ian Lipkin. Since last fall, beekeepers in at least 35 states have reported colonies that shrank rapidly for no apparent reason. Adult bees just go missing, leaving behind young bees in need of tending. This colony-collapse disorder (CCD), as it's now called, has got bee researchers coast to coast stirred up and looking for causes and remedies.

Lipkin, however, had never studied a bee disease until now. He works in the epidemiology department of Columbia University's Mailman School of Public Health--human health, that is. He's solved mysteries, though, and he says that his methods are yielding results this time too.

Lipkin is the pathogen hunter who in 1999 figured out that a cluster of people with encephalitis in New York had caught a then-obscure virus called West Nile. Since then, his lab has refined ways to use high-speed genetic sequencing to search for novel pathogens worldwide. What involved him in this insect-disease ease, he says, is "the same thing that has captured the imagination of the public--the notion that there's been this inexplicable loss of bees."

Following last winter's losses, beekeepers have had some success in rebuilding their hive numbers. But they remain concerned that next winter, their colonies may again suffer unexplained collapses.

It's a good mystery all right, with any number of hypothetical culprits: mites, bad bee food, cell phones, bee AIDS, pesticides, genetically modified (GM) crops, overwork. Jeff Pettis, based in Beltsville, Md., as head of the U.S. Department of Agriculture's network of laboratories devoted to bees, even suggested to the Washington Post that bees had worn themselves out making crop circles, thus explaining two mysteries at once.

Joking aside, Pettis, his government-bee-lab colleagues, Lipkin, and other researchers have been working in earnest on the problem. So far, they've eliminated several hypotheses. Now, they're mixing old-fashioned case study epidemiology with modern genetics. It now looks, says Pettis, as if "more than one factor may be coming together" in the mystery of the missing honeybees.

WHEN TO WORRY Beekeeper Dave Hackenberg, of Lewisburg, Pa., rents out his bees as migrant laborers, shipping hives around the country as crops come into flower and need pollination. Like baseball teams, his and many other big bee operations retire to Florida for the winter to get their workforce in shape for the stresses of the upcoming season.

But when Hackenburg checked on his hives there last November, he found that they were doing the opposite of recovering. He called Penn State University in University Park and reported that adult bees were disappearing without obvious cause.

Hackenberg's concern alerted researchers at Penn State and elsewhere to the problem, though Frazier says that once they started asking around, earlier eases turned up. In the typical case, colonies dwindled in a matter of weeks. Large numbers of bees simply vanished, and the few that remained showed a loss of appetite. Bees in neighboring colonies reacted oddly too. Instead of raiding an abandoned store of honey as soon as possible, they left the afflicted hive alone for days.

To start tracking down the cause of Hackenberg's troubles, state apiarist Dennis vanEngelsdorp, based at Penn State, and his colleagues undertook detailed case studies of affected beehives.

In mid-December of last year, van Engelsdorp's team released its first results. From interviews with seven beekeepers in four states, the researchers learned of substantial losses. One beekeeper expected to lose all but 9 of his 1,200 colonies. A hive can empty and collapse in as little as a week, the beekeepers said.

These interviews, and others that followed, didn't disclose an obvious cause for CCD, but they "ruled out some things," says Frazier.

Beekeepers said that they had procured queens from a variety of suppliers, so it seemed unlikely that a bad batch of queens had spread a disease or genetic problems to the colonies of their offspring. They used a variety of mite-controlling drug regimens on their hives, so the drugs weren't the obvious answer. And the colonies had been given several kinds of diet enhancements, such as corn syrup or protein supplements, so feeding practices didn't seem culpable.

What the bees did have in common, though, was recent stress, such as from a lot of travel between assignments. Stress could have left the colonies vulnerable to some other menace, the researchers speculated.

As news spread about the trouble last winter, bells rang for memories of past cases of honeybee-hive disasters, says Jay Evans of USDA's Beltsville, Md., bee lab. He cites a 1975 paper titled "Disappearing disease of honey bees" in the American Bee Journal. That report cited the paper "Bees evaporated: A new malady" in an issue of Gleanings in Bee Culture from 1897. These old reports raise the possibility that a bee pathogen is always lurking in hives but occasionally flares up in an especially virulent form. "It could be like the Spanish flu," says Evans. Flu is ever present, but the legendary 1918 epidemic killed an estimated 25 million people worldwide.