Beekeeper James Doan first began finding empty hives last fall. Entire bee colonies seemed to have up and vanished, leaving their honey behind. Noting the unusually wet fall in Hamlin, N.Y., he blamed the weather. Unable to forage in the rain, the bees probably starved, he reasoned.

But when deserted hives began appearing daily, "we knew it was something different," he says. Now, at the beginning of the 2007 pollination season, more than half of his 4,300 hives are gone. "I'm just about ready to give up," says Mr. Doan from his honeybee wintering site in Ft. Meade, Fla. "I'm not sure I can survive."

The cause of the die-offs has yet to be determined. Its effect on the food supply may be significant. Longer-term, it may also force a rethinking of some agricultural practices including our heavy reliance on human-managed bees for pollination.

Scientists call it "colony collapse disorder" (CCD). First reported in Florida last fall, the problem has since spread to 24 states. Commercial beekeepers are reporting losses of between 50 and 90 percent, an unprecedented amount even for an industry accustomed to die-offs.

Many worry that what's shaping up to be a honeybee catastrophe will disrupt the food supply. While staple crops like wheat and corn are pollinated by wind, some 90 cultivated flowering crops – from almonds and apples to cranberries and watermelons – rely heavily on honeybees trucked in for pollinization. Honeybees pollinate every third bite of food ingested by Americans, says a Cornell study. Bees help generate some $14 billion in produce.

Research is only beginning and hard data is still lacking, but beekeepers suspect everything from a new virus or parasite to pesticides and genetically modified crops. Scientists have hastily established a CCD working group at Pennsylvania State University. Last week, the US House of Representatives' Committee on Agriculture held hearings on the missing bees.

For many entomologists, the bee crisis is a wake-up call. By relying on a single species for pollination, US agriculture has put itself in a precarious position, they say. A resilient agricultural system requires diverse pollinators. This speaks to a larger conservation issue. Some evidence indicates a decline in the estimated 4,500 potential alternate pollinators – native species of butterflies, wasps. and other bees. The blame for that sits squarely on human activity – habitat loss, pesticide use, and imported disease – but much of this could be offset by different land-use practices.

Moving away from monoculture, say scientists, and having something always flowering within bee-distance, would help natural pollinators. This would make crops less dependent on trucked-in bees, which have proved to be vulnerable to die-offs.

The stress on honeybees grew as native and wild pollinators diminished and farmers came to rely more on honeybees. We've put "all of our pollination eggs in the honeybee basket," says Mace Vaughan, conservation director of the Xerces Society for Invertebrate Conservation in Portland, Ore. "We need more baskets."

An immune-system disorder?

Meanwhile, beekeepers are seeing hives empty in a matter of weeks, sometimes days. The entire adult bee population vanishes, except for a few juveniles. This makes CCD difficult to study. "You have a crime scene, you know a crime happened here, but you don't really have evidence," says Medhat Nasr, provincial apiculturalist in Alberta, Canada. Eerily, the stored honey in the hive remains untouched. Raiding bees from nearby colonies never materialize, as is common.

Records of suddenly empty hives go back as far as the late 1800s, but never on this scale. Beekeepers dubbed it "autumn collapse," "spring dwindle," or "disappearing disease." But Dennis vanEngelsdorp, the acting Penn State apiarist, calls this manifestation the AIDS of bees. The remaining juvenile bees appear to be rife with disease. To him, "It's clear that there is an immune suppression," he says.

What might suppress a bee's immune system is anyone's guess. But many ascribe to a tipping-point theory: A variety of factors may have accumulated until a single straw finally broke the bee's back.

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