CBS News correspondent John Blackstone reports researcher Jerry Bromenshenk has been tracking the bee die-off for four years. This year ranks with the worst.
The die off, known as "Colony Collapse Disorder," has killed about 30 percent of the hives in the United States over the past four winters. That's a total of three to four million hives gone, with a loss of billions of bees. Each hive can be home to 30,000 bees or more.
Watch a CBS News story on Colony Collapse Disorder
"In any small bee yard that you drive by when you're going down the road, there are more bees in that bee yard than there are people in L.A.," says Bromenshenk.
What's killing all those bees remains a mystery. At a scientific conference in San Francisco Thursday, researchers reported finding traces of 121 different pesticides in bee hives.
"That's a cause for concern," says USDA researcher Jeff Pettis.
Watch the Mystery of the Vanishing Bees
Pettis says the pesticides his group found may combine with other threats to bees.
"We're looking at pesticides just like we're looking at poor nutrition or parasitic mites as contributing to the overall decline in bee health," he says.
Being a bee has never been easy, with colonies frequently attacked by parasites and viruses. Until recent years, bees usually managed to cope with all that.
What's Killing The Honeybees?
Finding out why bees are no longer coping is getting urgent. Without bees to pollinate crops, we'd lose about a third of the food we eat.
"If you like something more than oatmeal for breakfast, if you like fruits and vegetables, things like that, that's the things bees contribute to our diet," says Pettis.
While its not unusual for people to be afraid of bees, perhaps what we should really fear is that one day we won't have them at all.