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When it comes to solving the puzzling syndrome known as "colony collapse disorder" (CCD), which has been attacking honey bee colonies since 2006, the best that can be said is that there is good news and bad news. The good news is that the rate of honey bee losses seems to have leveled offrather than continuing to increase. The bad news is that the cause or causes of CCD remain unclear.
In the United States, the problem surfaced in October 2006, when an increasing number of beekeepers began reporting losses of 30 to 90 percent of the hives in their apiaries with no apparent cause. The defining characteristic of CCD is the disappearance of most, if not all, of the adult honey bees in a colony, leaving behind honey and brood but no dead bee bodies. This definition has recently been revised to include low levels of Varroa mite and other pathogens, such as Nosema, as probable contributing factors.
For the last 3 years, self-reported surveys of beekeepers have found that winter colony losses have averaged about 30 percent, with around one-third of those losses ascribed to CCD, according to JeffPettis, research leader of the Bee Research Laboratory in Beltsville, Maryland, who heads up the Agricultural Research Service's CCD research effort. This compares to colony losses that were averaging 15-20 percent before CCD.
"The faint good news in the survey numbers is that the CCD problem does not seem to be getting worse," Pettis says. "But-and this is a big 'but'- 33-percent losses each year are probably not economically sustainable for commercial beekeeping operations."
While many possible causes for CCD have been proposed, reported, and discussed- both in the scientific literature and popular media-no cause has been proven. (See sidebar, page 7.)
"We know more now than we did a few years ago, but CCD has really been a 1,000-piece jigsaw puzzle, and the best I can say is that a lot of pieces have been turned over. The problem is that they have almost all been blue-sky pieces-frame but no center picture," Pettis explains.
The bee lab's scientists have been looking for the cause or causes of CCD within four broad categories: pathogens; parasites, such as Varroa mites or Nosema; environmental stressors, such as...