As growing season begins in California's Central Valley, there is nothing quite as busy as a beekeeper. Farmers pay them to put their hives in their fields and orchards.
"It means the difference between profit and loss for them," says beekeeper Lance Sundberg.
But beekeepers like Sundberg have a mystery in their hives this year. Bees are disappearing at an alarming rate.
"Colonies are going down. The bees aren't dead in the box or aren't out front," says Jerry Bromenshenk, a bee researcher at the University of Montana. "They've just disappeared. Just vanished."
Bromenshenk is leading a team of bee researchers looking for a cause. He's even listening to hives for signs of distress. Beekeepers in 22 states have reported bees dying in huge numbers.
Dr. Jerry Bromenshenk shows John Blackstone how colonies of bees have swiftly vanished.
Jeff Pettis of the U.S. Department of Agriculture says parasites and disease have killed bees in the past, but never anything like this.
"We went through multiple hives and we couldn't find anything that I would even call a beehive, so it was depressing," Pettis says.
Part of the mystery is that colonies can go from active and healthy to dead and gone within days. For beekeepers, that's a loss that stings.
They "just disappeared," says beekeeper Louise Rossberg. "There's nothing there. There's no bees on the ground anywhere. There's just a completely empty hive."
In just a few weeks, Rossberg has seen hundreds of her hives go empty. "I don't know what to do," she says. "And I'm not alone."
For now, plenty of beekeepers are stacking up silent and empty hives. But scientists are working hard to find the cause and a cure for what's ailing the bees. After all bees do for us, it's the least we can do for them.
For much more on this, visit the Web site of the American Beekeeping Federation by clicking here.