Worker bees take off

Go to work, come home.

Go to work — and vanish without a trace.

Billions of bees have done just that, leaving the crop fields they are supposed to pollinate, and scientists are mystified about why.

The phenomenon was noticed late last year in the United States, where honeybees are used to pollinate $15 billion worth of fruits, nuts and other crops annually. Disappearing bees also have been reported in Europe and Brazil.

Commercial beekeepers would set their bees near a crop field as usual and come back in two or three weeks to find the hives bereft of foraging worker bees, with only the queen and the immature insects remaining. The worker bees that survived were often too weak to perform their tasks.

If the bees were dying of pesticide poisoning or freezing, their bodies would be expected to lie around the hive. And if they were absconding because of some threat — which they have been known to do — they wouldn’t leave without the queen.

Since about one-third of the U.S. diet depends on pollination and most of that is performed by honeybees, this constitutes a serious problem, says Jeff Pettis of the U.S. Agricultural Research Service.

“They’re the heavy lifters of agriculture,” Mr. Pettis said of honeybees. “And the reason they are is they’re so mobile, and we can rear them in large numbers and move them to a crop when it’s blooming.”

Mr. Pettis and other analysts have gathered outside Washington for a two-day workshop that started yesterday to pool their knowledge and come up with a plan to combat what they call colony collapse disorder.

“What we’re describing as colony collapse disorder is the rapid loss of adult worker bees from the colony over a very short period of time, at a time in the season when we wouldn’t expect a rapid die-off of workers: late fall and early spring,” Mr. Pettis said.

Honeybees are used to pollinate some of the tastiest parts of the American diet, Mr. Pettis said, including cherries, blueberries, apples, almonds, asparagus and macadamia nuts.

“It’s not the staples,” he said. “If you can imagine eating a bowl of oatmeal every day with no fruit on it, that’s what it would be like” without honeybee pollination.

The problem has prompted a congressional hearing, a report by the National Research Council and a National Pollinator Week set for June 24 to 30 in Washington, but so far there’s no clear idea of what is causing it.

“The main hypotheses are based on the interpretation that the disappearances represent disruptions in orientation behavior and navigation,” said May Berenbaum, an insect ecologist at the University of Illinois, Urbana-Champaign.

There have been other fluctuations in the number of honeybees, going back to the 1880s, when there were “mysterious disappearances without bodies just as we’re seeing now, but never at this magnitude,” she said.

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