|August 03, 2007|
Can we save honey bees from Colony Collapse Disorder?
|Better Planet: Beepocalypse|
(by Josie Glausiusz) - Normally, the announcement that yet another species is in danger does not trigger economic jitters and hyperbolic headlines---but there is nothing normal about the disappearance of honeybees. The die-off has been rapid and inexplicable. The first reports surfaced in October 2006; within months beekeepers in 27 states, from Florida to California, reported a serious decline in the insects, and similar troubles were showing up in Canada and Europe. And honeybees, or Apis mellifera, are big business: Bee pollination of agricultural crops---everything from almonds to apples to carrots---provides one-third of the U.S. diet, and the bees' services are valued at $15 billion annually. If these six-legged laborers vanish, then many of the staples that we take for granted could be threatened---and a lot more expensive. By March 2007, Congressional hearings were under way to explore how Colony Collapse Disorder, as the bee syndrome has been dubbed, threatens America's agricultural vitality and what can be done about it.
There is no easy answer to the problem. Colony Collapse Disorder, or CCD, appears to differ significantly from previous bee maladies in that the bees simply fly away from the hive and never return, leaving behind only an egg-laying queen and a few young workers. Colony losses first seemed to be restricted to migratory beekeepers, merchants who transport hundreds of beehives from state to state, selling pollination services to farmers. Hypotheses proliferated: A brand-new disease is killing the insects. Pesticides are disrupting bees' ability to navigate. Parasitic mites are weakening them. Mite-killing chemicals, sprayed into the hives, are building up in the wax and eliminating the bees instead. It's a fungus. It's a virus. Maybe vibrations in the trucks that transport bees across the country are driving the little buzzers insane. Overwhelming stress is making the bees vulnerable to disease. And some of these conjectures sound truly loopy. The British newspaper The Independent ran an article anxiously asking, "Are mobile phones wiping out our bees?" It floated a baseless theory---citing a study that was not, in fact, carried out---that radiation from cell phones was disorienting the bees.
Further muddying matters, some researchers claim that the disorder is simply an extreme variant on an existing disease, pointing to similar, if smaller-scale, outbreaks of "disappearing disease" among bees that struck in the 1930s and 1970s, with equal lack of explanation. But everyone agrees that something peculiar is happening, and nobody knows exactly why.
Nancy Ostiguy, an entomologist at Penn State University, sees signs that the culprit is a new pathogen. She notes that the abandoned colonies are filled with food. Normally, neighboring bees would swoop into forsaken hives and steal honey and pollen. Yet neither robber bees nor pests like wax moths and small hive beetles are entering the emptied bee boxes. "One of the working hypotheses is that there is a fungus that hasn't been in the colonies before," Ostiguy says. "The hypothesis is that this fungus, which either has killed the bees or come in later, is producing a toxin." The toxin might be so repellent that the bees desert the hive.
Axel Decourtye, an ecotoxicologist at the Association de Coordination Technique Agricole in Marcy l'Étoile, France, is looking instead at a chemical cause. He is focusing on a class of insecticides called neonicotinoids, and in particular imidacloprid, which is used to coat sunflower seeds and then suffuses the plants' tissues as they grow. His studies have shown that imidacloprid can impair honeybee memory and their ability to learn new odors, which leads biologists to suspect that forager bees exposed to this pesticide might become lost and die far from the hive. Yet even after France banned imidacloprid in 1999, honeybee populations in France continued to plummet, according to Decourtye's collaborator Nicolas Desneux of the University of Minnesota. "There are no experimental field data so far showing that these products are responsible for the global decline in bee populations," Desneux says. Still, no one has shown that agricultural pesticides---and there are quite a lot of them---are not a cause of CCD.
Amidst this perplexity, other researchers are searching for ways to save the bees before it is too late. One tactic is to boost the insects' ability to defend themselves against parasites and pathogens. Since 1993 Marla Spivak, an entomologist at the University of Minnesota, has been breeding a strain of honeybee that can smell the rotting odor of American foulbrood, a bacterial infection, as well as the yeasty whiff of chalkbrood, a fungal disease; they can also detect parasitic varroa mite infestations in young bee pupae. Spivak's custom-bred worker bees can patrol the hive, pierce the cells in which affected offspring are growing, and remove them---and sometimes eat them---before disease or parasites have an opportunity to spread through the hive.
Although such "hygienic bees" would eliminate the need for antibiotic applications in hives, Spivak admits that they are unlikely to provide a long-term solution to Colony Collapse Disorder. She believes its causes are multiple: mites and viruses, residues of chemical mite killers, cross-country transportation, nutritional stress from tainted corn-syrup feed or pollen supplements, and pesticide exposure. "In my mind those symptoms are not new. Abandoning the nest---many things would cause that."