STATE COLLEGE, Pa. - A mysterious illness is killing off tens of thousands of honeybee colonies across the country, threatening the livelihood of commercial beekeepers and sending researchers scrambling for a cause.

The ailment termed "Colony Collapse Disorder" could affect domestic honey production in the United States and, perhaps even more importantly, put a strain on fruit growers and other farmers who rely on bees to pollinate their crops.

Reports of unusual colony deaths have come from at least 22 states, and some affected commercial beekeepers - who often will keep thousands of colonies - have reported losing more than 50 percent of their bees. A colony can have roughly 20,000 bees in the winter and up to 60,000 in the summer.

"We have seen a lot of things happen in 40 years, but this is the epitome of it all," Dave Hackenberg, of Lewisburg-based Hackenberg Apiaries, said by phone from Fort Meade, Fla., where he was working with his bees.

Most plants need to be pollinated by birds, bees, bats and other animals and insects to reproduce. A recent report by the National Research Council noted that in order to bear fruit, three-quarters of all flowering plants - including most food crops and some that provide fiber, drugs, and fuel - rely on pollinators for fertilization.

Hackenberg, 58, was first to report the problem in November to bee researchers at Penn State University. He was down to about 1,000 colonies after having started with 2,900 in the fall.

"We are going to take bees we got and make more bees ... but it's costly," he said. "We are talking about major bucks. You can only take so many blows so many times."

One beekeeper who traveled with two truckloads of bees to California to help pollinate almond trees there found nearly all of his bees dead upon arrival, said Dennis vanEnglesdorp, acting state apiarist for the Pennsylvania Department of Agriculture.

"I would characterize it as serious," said Daniel Weaver, president of the American Beekeeper Federation. "Whether it threatens the apiculture industry in the United States or not, that's up in the air."

Scientists at Penn State, the University of Montana and the U.S. Department of Agriculture are among a quickly growing group of researchers and industry officials trying to solve the mystery.

Like detectives just arriving at a murder scene, researchers are still assembling clues. Here is some of what they know so far:

_Typically, the bodies of dead bees are littered around the hive, sometimes carried out of the hive by worker bees after dying. But no bee remains are typically found around colonies struck by the mystery ailment. Scientists assume these bees have flown far away from the hive and died.

_From the outside, a stricken colony may appear normal, with bees leaving and entering the hive box. But when beekeepers look inside the hive box, they find few mature bees taking care of younger, developing bees.

_A weakened bee colony will normally be immediately overrun with bees from other colonies or other pests that will try to raid the hive of honey. That's not the case with the colonies of stricken bees, and those hives may not be touched for at least two weeks, said Diana Cox-Foster, a Penn State entomology professor investigating the problem.

"That is a real abnormality," Hackenberg said.

The disorder seems to be striking colonies quickly.

"Some of these guys thought they had the strongest colonies they had for a long time, then came back two weeks later and the entire apiary or cluster of colonies were all gone," Cox-Foster said.

In lab specimens of dissected bees, Cox-Foster said she has found was an alarmingly high number of foreign fungi, bacteria and other organisms and weakened immune systems.

The country's bee population had already been taking a hit in recent years because of the parasitic varroa mite, which had destroyed more than half of some beekeepers' hives and devastated most wild honeybees.

Researchers are also looking into how pesticides might be affecting bees.

The role of bees and other pollinators in the food chain was of such importance that the National Research Council released a study on population issues in October. It found honeybees to be among the hardest-hit pollinators, with bees having to be imported from outside North America last year for the first time since 1922, the report said.

Meantime, word of mouth is spreading now among beekeepers wondering if bee deaths over the last couple of years once attributed to mites or poor management might actually be due to the mystery ailment.

"We certainly started thinking it was a fall problem," vanEnglesdorp said. "Now people think that they may have had this three or four years."

Hobbyists with fewer colonies, or those who may raise bees to sell honey at a roadside stand, may have to wait a little while to check on their bees, especially in northern climates. Bees don't like to be out in cold winter temperatures.

Charlie Vorisek, of Linesville, has 88 colonies, and takes the unusual step of housing them during the winter inside a barn, where it is a little warmer. Vorisek last year bought about half of his colonies from a larger beekeeper who went out of business after many other bees died from the mystery ailment.

Vorisek said he has lost four his 44 holdover colonies. He's lost 27 of the 44 colonies he recently purchased.

"I was of the mind that I could keep them alive," he said. "But some of them look like they'll be OK."

ON THE NET

Mid-Atlantic Apiculture: http://maarec.cas.psu.edu/index.html

Penn State University Entomology Dept.: http://www.ento.psu.edu/

http://www.philly.com/mld/philly/news/16677033.htm