Fewer beekeepers reported colony losses this winter from a mysterious, yet deadly, bee malady than they have the past few years.

Nevertheless, they still reported losing 29 percent of their colonies from September 2008 to April 2009, according to the survey conducted by the Apiary Inspectors of America and the U.S. Department of Agriculture.

This is less than the 36 percent loss from 2007 to 2008 and the 32 percent loss from 2006 to 2007.

"While the drop in losses is encouraging, losses of this magnitude are economically unsustainable for commercial beekeeping," Jeff Pettis, research leader of the Agricultural Research Service Bee Research Laboratory, said in a news release.

About 26 percent of apiaries surveyed reported that some of their colonies died of colony collapse disorder, down from 36 percent of apiaries in 2007-2008.

CCD is characterized by the sudden, complete absence of honey bees in a colony. The cause of CCD remains unknown.

Since the survey was based only on interviews, it's not possible to confirm whether CCD was the culprit in all of the colony losses.

The survey involved beekeepers who represented about 20 percent of the country's 2.3 million colonies.

To view an abstract of the data, visit http://maarec.cas.psu.edu.