In late 2006, whole hives of honeybees began dying overnight--victims of an unknown syndrome. Though the die-offs have afflicted nearly a quarter of U.S. beekeeping operations, scientists still aren't sure what causes them, but they've narrowed down the suspects:
A team of scientists chiefly from Penn State and Columbia universities and the U.S. Department of Agriculture took samples from hives that had been afflicted with colony-collapse disorder (CCD)--the term for the syndrome wiping out the bees--and decoded the genetic material inside them. In a paper published in Science Express on Sept. 6, the group reported that one pathogen-- the recently discovered Israeli acute paralysis virus (IAPV)--was present in more than 90% of the samples, indicating that IAPV might be at least a good marker for CCD, if not a direct cause.
What the Doubters Say: Another group of researchers, which collaborated with the U.S. Army, has done its own studies on CCD-afflicted hives and found no clear links with IAPV. Also, the virus came to the U.S. from Australia, but there's been no CCD Down Under.
A host of microscopic bugs afflicts honeybees, including the vampiric Varroa destructor, which sucks the blood of bees. The mites first appeared in the U.S. in 1987, and they've taken a severe toll on honeybees, which had been in decline even before CCD. The bites of the mites don't kill the bees, but they produce open wounds that leave the insects prone to further infections. Tracheal mites, which attack the respiratory system, are also a suspect.
What the Doubters Say: If Varroa is the sole cause, why did CCD not appear until late 2006? It's more likely that Varroa is working in concert with other parasites or pathogens to wear down bees' immune systems until the slightest thing can kill them. One reason to believe this: many hives have experienced CCD without the presence of the vampire mite.
Pollinating bees may be a farmer's best friend, but that doesn't save them from being accidentally dosed by the pesticides used to rid fields of less welcome insects. One suspect is Imidacloprid, an insecticide ingredient discovered by Bayer. Now banned in France, it's been blamed for triggering a decline in bee populations. (Bayer denies that Imidacloprid is behind CCD.)
What the Doubters Say: Despite France's 1999 ban, bee numbers there continued to drop. Studies of CCD have found no common environmental factor, meaning that Imidacloprid too could be simply one of many causes. All the unanswered questions have beekeepers buzzing. "Something out there is ruining my livelihood," says David Hackenberg, the Pennsylvania beekeeper who first reported CCD. "And there's nothing I can do about it."