It's a mystery why U.S honeybees are abandoning hives in alarming numbers. But it's happening and if answers to the mass exodus — called colony collapse disorder — aren't found soon, the implications for agriculture will be huge.

Last summer, calls and reports from beekeepers began reaching Gary Hayes.

“Unfortunately, beekeepers have struggled over the last few years from colonies dying from introduced parasitic mites and other things,” says the president of the Apiary Inspectors of America from his Gainesville, Fla., office. “They're already kind of numb because of all the problems. But last summer, beekeepers began losing colonies for reasons that weren't quite in line with the other problems.”

Over the course of a few weeks, beekeepers noticed colony bee numbers would dwindle as the insects simply disappeared. Foragers would go out to find flowers and wouldn't come back.

“With affected hives, there are no dead or dying bees on the ground as we see with pesticide exposures or other diseases. No one can explain this behavior.”

Over time, the gradual abandonment means all that's left in a colony is a queen, a few attendants, eggs and brood (baby bees). Bees are an extremely social insects and for them to leave a colony in great numbers is very odd.

And often the few bees left behind appear to suffer from an immune system collapse. The bees seem to be susceptible to bacteria and fungi that normally would cause no bother.

“That, too, is highly unusual, and we've been trying to find the cause for several months. It seems to indicate some sort of mass immune deficiency. There are some very smart people looking for an answer, but we still haven't come up with a smoking gun that we can combat through management practices or something else. It's quite frustrating.”

Beekeeper services are vital for U.S. agriculture because there are no longer many wild honeybees.

The wild honeybee population is repopulating “a bit,” says Ed Levi, of the Arkansas State Plant Board. “But we lost a huge number of wild bees when the tracheal mite and Varroa mite came into the country. In the last 20 years, or so, we're down to less than 5 percent of the feral colonies we used to have.

“Now, that doesn't include the Africanized bees that are moving into more areas of the United States. And they have some natural resistance to the mites.”

(For more on Africanized bees in Arkansas, see http://deltafarmpress.com/news/061129-africanized-bees/index.html)

The honeybee is being impacted “significantly” on many fronts, says Harry Fulton, of the Mississippi Bureau of Plant Industry. “And that's not good because honeybees are responsible for a third of the food we eat daily.”

As an example of what honeybees face, Hayes says to make a fist and place it next to your body.

“That's how large a Varroa mite is to a honeybee. And these mites suck a bee's blood. Obviously, that debilitates and weakens their immune systems. The mites also vector viruses that affect honeybee health.”

Normally, honeybees forage within a 2.5-mile radius of their colony. They visit flowers to collect pollen and nectar to make honey to feed themselves and their young. That means they're exposed to whatever is in the environment.

“Of course, honeybees are exposed to agricultural chemicals sprayed on crops or used systemically to control pests,” says Hayes. “Those pests are mostly insects, but so are honeybees. Even at sub-lethal levels, some of the chemicals can find their way through plant nectar and pollen to the bees.”

Researchers are also looking into any possibility that GMO crops could be playing a role in the bees' behavior. “There are some concerns about GMO crops that can produce a toxin used to battle harmful insects. Those traits are also in nectar and pollen.”

Like farmers, beekeepers have always been independent and resourceful. Even though they've grown accustomed to hive losses of 30 percent annually — primarily from Varroa mites — they've been able to survive.

“The primary way commercial beekeepers stay ahead of mites and other problems is to divide colonies and build numbers back,” says Hayes.

To illustrate how this works, Mississippi is home to “quite a few” migrant beekeepers, says Fulton. “There are probably 20,000 hives moved here each fall or winter. The beekeepers usually split them two or three times, so around 50,000 hives leave Mississippi.”

Fulton says he hopes the Mid-South — so far less affected by colony collapse disorder than other areas — will remain free of the problem. However, “it's hard to prevent something when you don't know what to avoid.”

It is now common for Hayes to hear of beekeepers losing over 50 percent of their hives to colony collapse disorder. “If you have that kind of loss, you can't build up to what you had before.”

That's led to a dwindling of colony numbers and beekeepers can't keep up.

“We've had reports of beekeepers forced out of business. They can't fulfill pollination contracts. Other businesses that normally provide queen bees are canceling orders. They don't have enough bees to work with.”

At some point, warns Hayes, “the lines on the graph will cross and there won't be enough honeybees in the United States to pollinate our crops.”

To find answers to the cause or causes of colony collapse disorder, government and university researchers are using an identification-by-elimination process.

“They're looking for things affected beekeepers don't have in common — they can assume those aren't the cause,” says Levi. “Then, of course, they're looking at what the affected operations do have in common.

“Taking all that information, they've narrowed down the possibilities. That doesn't mean the nail has been hit on the head. But all the possibilities concern stresses on the bees of some sort.”

Many of the beekeepers experiencing this problem are “commercial and large,” says Hayes. “Lots of them are migratory, moving their bees to different crops as they're needed.

“The bees seem to be stressed from either the migration or colony splits. Large beekeepers, especially, have a tendency to split colonies to make more. There's been stress from over-splitting.

“There are also concerns about sub-lethal levels of pesticides — that's a discussion we've been having for years.”

Levi says the researchers are “working as hard as they can. Recently, many went out to California to look at the bees there for the almond crop. They were able to work around a massive number of colonies. They've found the same symptoms there: beekeepers losing 30 to 80 percent of their colonies. They aren't finding many bees either in or outside affected colonies. The bees just vanish.”

Colony collapse disorder has been found in 30 states, including Hawaii, and isn't affecting beekeepers equally. Some have suffered dramatic losses — going from thousands of colonies to hundreds of colonies. Others have only had a few hives affected.

“For commercial beekeepers it does seem more dramatic because they keep such huge numbers of bees. But we have plenty of reports of the problem from smaller beekeepers and hobbyists. As spring arrives, we're now getting reports from further north.”

Is there any chance bees are leaving to set up other hives?

“No, this isn't swarming or absconding,” says Levi. “A swarm is when a colony splits through asexual reproduction. When that happens, part of a colony will leave and find a home elsewhere. That's totally natural.

“Then, sometimes bees abscond. That's when conditions become so severe and difficult in a colony's area that the whole thing will leave.”

Neither of those is happening with colony collapse disorder.

“With this, a strong or, at least, seemingly robust colony has foragers, older adults bees, that don't return. Then, the next generation of bees will age and do the same. Over the course of six weeks, or so, the hive is abandoned.”

Honey is a wonderful food. “But honey is a byproduct of pollination and that's the gift that honeybees really provide us,” says Hayes. “The USDA projects by 2015, the U.S. will be importing 40-something percent of our vegetables. In 50 years, it estimates, we'll be a net importer of food.”

Hayes says the bigger question from a strategic standpoint is how much U.S. food production “do we want to turn over to someone else? Would that mean we'll be in the same predicament we're now in with oil?

“This situation is alarming and scary. Are honeybees the canary in the coal mine? Is this situation telling us something is askew in the environment?”

Whatever the case, a solution to colony collapse disorder is desperately needed.

“Unfortunately, historically, honeybee research hasn't gotten the kind of funding it deserves, considering the vital role honeybees play in agriculture,” says Levi. “The universities and USDA labs working with bees are underfunded. That needs to change.”

(Editor's note: for more information, visit http://maarec.cas.psu.edu/index.html.)