JEFFREY BROWN: It's been five years since honeybees started dying in large numbers across the country. Scientists are still trying to figure out why and what they can do about it.
NewsHour correspondent Spencer Michels has an update.
SPENCER MICHELS: In a field of sunflowers in California's Central Valley, it's obvious not all the bees have disappeared. Despite five years of mysterious trouble in American honeybee hives and devastating die-offs that continue to happen, bees are still pollinating 130 kinds of fruits and flowers worth $15 billion.
What agriculture and scientists continue to fear is what they call colony collapse disorder, or CCD, will remain unchecked, unsolved and destructive.
California beekeeper Randy Oliver had this happen to his hives.
RANDY OLIVER, California beekeeper: With the colony collapse, it's very sudden, where you see the colony just kind of teetering, still full of bees. Then, boom, overnight, all the bees are gone.
SPENCER MICHELS: Here at the University of California at Davis, scientists are trying to find ways to improve health of the bees, partly by changing what they eat, partly by selective breeding of healthier, disease-resistant bees.
A new garden of bee-friendly plants has been planted at Davis courtesy of an ice cream manufacturer, whose business depends on fruits pollinated by honeybees and who is funding research.
Eric Mussen has been the university extension apiculturist throughout the colony collapse crisis. Mussen is frustrated that the disease is still rampant, though not for all beekeepers.
ERIC MUSSEN, University of California, Davis: We really don't seem to have accomplished a whole lot, because we're still losing, on an average, approximately 30 percent or more of our colonies each year. And that's higher than -- than it used to be. Only 25 percent of the beekeepers seem to have this CCD problem over and over and over. The other 75 percent have their fingers crossed and say, I don't know what this is, but it's not happening to me.
SPENCER MICHELS: In Joe DeRisi's University of California, San Francisco lab, scientists are now using the tools they developed for studying human pathogens to hunt for the culprit in colony collapse disorder.
JOE DERISI, University of California, San Francisco: One of the frustrating things with CCD is, it doesn't look like there's any one single agent or culprit. Imagine if you had the cold, and you got the flu on top of a cold. Well, that might be the case with the honeybees. You have a weird fungus and a virus, and it causes a drop in the health of a colony to the point where the colony can't maintain itself.
SPENCER MICHELS: Scientists working with DeRisi essentially are starting from scratch. Using a modified vacuum cleaner, they collect healthy bees from nearby hives to try to figure out what pathogens normal bees contain, so they can recognize abnormal when it occurs.
Michelle Flennekin is a postdoc microbiologist.
MICHELLE FLENNEKIN, University of California, San Francisco: Honeybee colonies, kind of like human populations, are exposed to a number of viruses and pathogens throughout the whole -- the entire course of the year. So what this study provides us is a normal, healthy colony baseline of the ebb and flow of the microbes associated with that colony throughout the course of the year.
SPENCER MICHELS: In the lab, Flennekin's colleague Charles Runckel smashed up the dead bees, in order to extract DNA or RNA and analyze what viruses or bacteria are present.
As part of their study, they followed and got samples from a huge commercial beekeeping operation as it traveled across the country pollinating crops. Their work has already paid off.
CHARLES RUNCKEL, University of California, San Francisco: We found four new viruses in this study, and one of them was so frequent, it was more -- there was more of that virus present than every other virus that we have know about put together.
SPENCER MICHELS: Finding such normal viruses makes finding the causes of CCD more likely.
CHARLES RUNCKEL: Once you know each of these viruses and you know their genetic makeup, you can look for them very easily. But finding them in the first place takes years and a lot of effort. And so that's what we did here, the first step.
SPENCER MICHELS: Still, the progress has been slow since scientists are starting with little knowledge of bees and bee diseases.
JOE DERISI: In comparison to what we know about human biology and the infectious diseases that affect all of us, we know almost nothing about honeybees, for which we depend so much. This is what I think CCD has really done, is brought new science, new interest and new researchers into the game.
SPENCER MICHELS: But that hasn't yet helped beekeepers trying to keep their hives alive. In Grass Valley, Calif., Randy Oliver rents out 1,000 hives to make his living. He's experienced die-offs before, but this one has been more persistent.
When his colonies collapsed, he started experimenting and reading the scientific literature. He agrees with DeRisi that several factors are at play in this perfect storm that he figures weakens the bees' immune system.
RANDY OLIVER: The first one is bees are stressed by the cold. They're a tropical insect. The second one is any kind of pathogens, parasites, viruses, bacteria. The next one is nutrition. And that's critical, for the bees to get good nutrition, or they can't fight the pathogens. And the last one is pesticides.
SPENCER MICHELS: Oliver and others have started splitting their hives every year, taking half the bees out and starting a new hive. He calls it "forever young," and it seems to keep the bees healthy.
RANDY OLIVER: That simple act of splitting gives the bees a fresh start. And, in nature, that's what they do. Bees -- bees reproduce frequently. They swarm every spring, and they give themselves fresh starts. And that's what beekeepers are tending to do, too.
SPENCER MICHELS: In the field, Oliver is running controlled tests of a natural antiviral product, one of several remedies promoted by private industry.
At his home, Oliver examines bee tissue under the microscope for pathogens to see what conditions, what foods may be associated with CCD. It's a continual fight, he says, a fight that's easy to lose, given the nature of bees and pathogens.
RANDY OLIVER: You have to be running all the time to stay in place, that because the pathogens never stop evolving -- the viruses evolve constantly. The fungi evolve constantly. The parasitic mite is evolving constantly. If the bees are not constantly evolving, the parasites will overwhelm them.
SPENCER MICHELS: So far, the consensus is that most beekeepers are avoiding colony collapse disorder though careful management of their bees. But the disease, whatever it is, has not gone away, and scientists ruefully admit they don't yet know what causes CCD or how to cure it.