Despite getting fewer headlines in recent years, the population of U.S. honeybees has continued to plunge, with billions dying each year from a condition known as colony collapse disorder (CCD). The demise of the bees is now raising greater concerns about the cost to the nation's food supply and the sustainability of the beekeeping industry itself.
Part of the problem, according to a new report by the Department of Agriculture , is that finding a specific cause of CCD remains elusive.
"It's like a perfect storm of reasons," said Kim Kalpan, a public affairs spokesperson for the research service of the U.S. Department of Agriculture.
"We've eliminated that it's one single cause. We're looking at several causes, including parasites, poor nutrition for the bees, viruses and drought conditions," Kaplan said. "We just don't know what it is at this point.
CCD has been around in the U.S. since 2006, when more than one quarter of the 2.4 million honey bee colonies were lost. Each year, more and more bees die.
(Read more: When It Comes to Health-Care Reform, the IRS Rules)
According to the USDA, bee losses from CCD this past winter were 31.1 percent of all colonies. That's up from 22 percent the previous winter and slightly higher than the previous six-year loss average of 30.5 percent. It's estimated that 10 million beehives have been lost in the last six years at a cost of $2 billion, according to the USDA.
"It's a major issue because 70 percent of bee keepers are reporting losses higher than is economically possible for them to stay in business," said Kaplan. "Usually, they can sustain a loss of 15 percent a year, but this higher number is really bad."
"What happens is that bees get scarce when beekeepers go out of business, and that means pollination contracts go up in price and that means higher prices for consumers," Kaplan explained.
Besides making honey, honey bees pollinate more than 100 crops including apples, zucchini, berries, broccoli, nuts, asparagus, celery, squash, peaches, soybeans and all citrus fruits. A lack of bees to pollinate them has the government worried.
In a report issued last October, the USDA said the "survivorship of honeybee colonies is too low for us to be confident in our ability to meet the pollination demands of U.S. agriculture crops."
(Read more: Dicey US Corn-Planting Weather to Continue )
Almonds provide an example of the concern. In California, where 80 percent of the world's almonds are grown, a lack of local honey bees hives is forcing the state to ship in bees from around the country in order to keep up with demand.
"We have to be worried about the impact on the food supply if we continue to see the loss of hives," said Bernard Weinstein, an economist at SMU. "It's not clear that food prices have been affected by the hive loss yet, but sometime down the road it could be a problem."
While the USDA says it doesn't know the root causes of CCD, it can say what doesn't cause it.
"There have been misinterpreted reports of cell phones, cell phone towers and cordless phones being responsible for CCD," said Kaplan. "We can definitely rule those out."
(Read more: Droughts Put US Energy Supply in Peril)
Until a cause of CCD is found, honeybee keepers are being urged to try and keep their bees healthy through good nutrition. Analysts also say the work of pollination may be picked up by other insects and birds, but that would hardly make a remedy. The U.S. is importing some honeybees, but not at levels to really make a difference at this point.
Honeybee hive losses have happened before, according to the USDA. In 1903, 2,000 colonies were lost to an unknown disease in Utah. There have been other periods of major losses in the 1920's and 1960's.
"I don't think honeybees are going to disappear completely," Kaplan said. "But we've got to figure this out before it gets worse."
More From CNBC
- US Sees Bigger April Surplus as Deficit Narrows: CBO
- Corporations Find a Friend in the Supreme Court
- Sequestration Cuts: Some Cope, Others Out of Luck
- Politics & Government
- honey bees