Upcoming laboratory and field tests, coupled with a survey of beekeepers this spring, may help provide the key to scientists' search for the cause of widespread die-offs among honeybee colonies in the United States.

The problem, says one expert in the field, may be a combination of pesticides and pathogens.

"We don't have our smoking gun. ... [but] we're getting closer," said Dewey Caron, an entomologist who recently retired from the University of Delaware.

While hives may lose 10 percent of their population during an ordinary winter, in recent years those losses have shot above 30 percent, Caron said last weekend at a beekeeping workshop in Little Creek.

The die-offs, dubbed "colony collapse disorder," have attracted a tremendous amount of attention and research in the apiculture field.

Members of the Delaware Beekeepers Association will hear some of the latest research from U.S. Department of Agriculture and Pennsylvania State University experts at a conference later this month.

A beekeepers' survey on losses to be conducted soon by the Mid-Atlantic Apiculture Research and Extension Consortium may help provide additional clues, said Caron, who is a member of the group's colony collapse disorder task force.

One of the theories being pursued most aggressively, he said, is that bees are dying of the same diseases they've always suffered from, but their immune systems are being overloaded by the heavy use of pesticides.

That includes pesticides applied by beekeepers themselves, he said.

"Instead of one disease, we have several," Caron said. "The pesticides are tying up the way they fight these things."

Perhaps paradoxically, the widely reported problems among bees have attracted more people to the hobby, said Bill Leitzinger, a vice president of the Delaware beekeepers' group.

"Suddenly, people are interested, which is a great focus," he said. "It's a fairly easy hobby."

Caron said bees have a "very thin library" of actions to protect against disease. Their basic evolutionary strategy has been to simply get busier -- produce more bees -- but that hasn't been working in this case, he said.

The pesticide theory, Caron said, isn't about a one-time application of pesticides, but rather a chronic level of exposure, as they build up in bees' wax pods.

Pesticides have been one tool in beekeepers' arsenals to fight off mites, which can feed on bees' blood.

"They're a very short-term answer that gives us a long-term problem," Caron said.

There are organic, non-chemical-based alternatives to fighting mites, Leitzinger said, including a simple one: Powdered sugar. Beekeepers can sift the sugar into a hive, which coats the bees and knocks the mites off.

Caron agreed that natural techniques may be the best way to combat the still-unknown problem.

"Now we're going much more toward the organic," he said. "The shift has been very nice."