The Honeybee Mystery
Entomologist Discusses Colony Collapse Disorder
by Don Miller
Humans have coveted honeybees’ sweet products for millennia. A 12,000-year-old cave painting from Valencia, Spain, depicts what is unmistakably a woman carrying a basket in one arm while plunging her other arm into a bee tree as the excited bees buzz about. In modern America, high-fructose corn syrup has relegated honey to a quainter, quieter corner of the market, although the pollination services rendered by honeybees remain critical to our multibillion-dollar agricultural industry.
The sudden and widespread decline in honeybees, known as colony collapse disorder (CCD), has prompted the hasty establishment of a scientific CCD Consortium and hearings on the missing bees at the U.S. House of Representatives’ Committee on Agriculture.
Along with dogs, dromedaries, and cats, humans have domesticated honeybees, though, like cats, bees can be difficult to herd. Honeybees are prone to abandon their hives, and controlling bee pedigrees through artificial insemination of the queen is a most delicate undertaking. For the most part, however, domestication has afforded honeybees some measure of security while beekeepers have reaped bee products and services in turn. A major break for bees and their keepers came in 1852, when the Rev. L. L. Langstroth invented the modular wooden hive with removable wax frames. Rather than harvesting honey by destroying the whole colony, beekeepers could open, inspect, harvest, and replace individual frames while disturbing the bees only minimally. Hives could be expanded to accommodate colony growth, reducing the bees’ impulse to abandon crowded quarters.
The labor we exploit in honeybees is staggering. To produce a pound of honey (the average quantity an American consumes per year) requires a total number of bee-miles roughly equivalent to one trip around the globe. Honeybees pollinate about 90 cultivated crops, including almonds, apples, canola, and watermelons, helping to generate $14 billion in produce. No one seriously imagines replacing legions of honeybees with human laborers armed with brushes, yet CCD poses a potentially devastating threat that could upend the industry.
One of the oddest aspects of CCD is that adult worker bees simply go missing. On inspection of “dead” or collapsed hives, beekeepers report finding plenty of food stores and juvenile bees in stricken colonies, but an absence of adult bees, dead or alive. Where colonies are undergoing collapse, the queen is present, but the adult work force is very small and consists solely of young bees carrying out domestic chores like tending the larvae. Because afflicted bees are sluggish and appear immuno-compromised, CCD has been dubbed the “AIDS of bees.”
To construct an overall picture of factors linked to CCD, the consortium interviewed professional beekeepers in 10 states, including California. All had experienced heavy losses of from 30 to 90 percent of their hives. All moved their bees on a regular basis and recycled their equipment and bee brood from dead colonies to existing, strong ones. Apparently, both practices may facilitate the spread of pathogens responsible for CCD, and the consortium is sampling and monitoring suspect colonies for such microbial enemies.
No single explanation for CCD has yet been identified; instead, the decline may be due to a conspiracy of bees’ natural enemies, which include ants, wax-eating moths, parasitic mites, and microbes like bacteria and fungi. The stress of moving bee colonies long-distance also takes its toll (about 70 percent of the nation’s commercial hives are trucked in to California almonds each February).
It is unclear whether other human practices, such as spraying pesticides, may be implicated as well. In the 1990s, French beekeepers suffered great losses from “mad bee disease,” a malady similar to CCD in which foraging bees failed to find their way home. The pesticide Gaucho was a suspect, and the government banned it, but no clear link was established.
In Germany, where beekeepers have recently lost 25 percent of their hives, one study implicates crops genetically modified for a gene for the insecticidal toxin Bt. But on March 27 of this year, the American CCD Consortium stated that it had found “no evidence thus far of any lethal or sub-lethal effects of Bt proteins on Honeybees.”
Whatever the causes of CCD, the crisis is of a magnitude sufficiently great to raise serious questions about depending so heavily on a single species—Apis mellifera—to pollinate so many of the crops on which we depend. Growers might consider diversifying the number of pollinating species to get the job done. The honeybee is but one of more than 30,000 species of bee, most of which live solitary lives but, like the honeybee, visit flowers for pollen and nectar. Many bees native to North America have the potential to assist in pollinating crops, though in only a few cases have the specifics of bee husbandry been worked out.
In Butte County, researchers are actively investigating the potential of the blue orchard bee to pollinate almonds. Because this bee nests solitarily, beekeeping techniques will necessarily differ from those for the honeybee. The blue orchard bee is a more efficient carrier of pollen and more active in cold weather. And, perhaps best of all, the blue orchard bee does not suffer from colony collapse disorder.
—Don Miller is the entomologist in the Department of Biological Sciences