Spring’s return this week brought visits by busy honeybees to winter jasmine and a lingering question regarding the health of our pollinators. The appearance of a deadly new phenomenon called Colony Collapse Disorder or CCD grabbed national attention in 2006 when many commercial beekeepers reported unusually large losses of honeybee colonies in several locations in the United States. When CCD strikes a hive, worker bees simply disappear leaving behind the queen, a few attendant workers, and cells full of pollen and brood. Without a full contingent of hardy workers, the queen and brood are doomed and the colony collapses.
Magnitude of problem
Soon after CCD was discovered national surveys of beekeepers were conducted to determine the magnitude of the problem. Between September 2006 and March 2007, beekeepers lost approximately 32% of their hives. During a similar period in 2007 and 2008, beekeepers lost about 36% of their colonies. Results of the most recent survey reported in May, 2009 had some good news. During the winter of 2008 to 2009 total losses of managed honeybee colonies were about 29%. In the winter of 2007 – 2008 CCD, 60% of colony loss was attributed to CCD, but in the winter of 2008-2009 only about 15% of colony loss appeared to be related to CCD. The bad news is that while losses due to CCD declined, colonies still did not fare well and 58% of beekeepers reporting abnormally high losses during the winter of 2008 – 2009.
Cause of CCD
The cause of CCD is not fully understood, but researchers have made great progress identifying some of the culprits in this mystery. The introduction of Varroa mites in the late 1980’s decimated the bee industry in the United States. Varroa mites infest honeybees and suck blood from larvae, pupae, and adults, particularly male bees. Not surprisingly, this weakens bees and predisposes them more serious diseases. Varroa mites have also been implicated in transferring viruses that attack or cripple bees such as acute bee paralysis virus and deformed wing virus. It appears that several primary stress agents including Varroa mites, pesticides, and less than optimal sources of pollen impose physiological stress on colonies of bees. Pesticides are regularly used to manage pests of crops and honey bees may encounter residues in nectar and pollen. Even pesticides used to combat Varroa mites may accumulate in beeswax in the hive. As bees return with nectar and pollen, pesticides can accumulate in comb and other products including honey. Pesticides are thought to further stress bees and weaken their immune system predisposing them to diseases. In addition to viral diseases mentioned previously, honey bees are susceptible to a nasty single celled, fungus-like organism called Nosema. Nosema hits worker bees the hardest with symptoms of dysentery and a reduced ability to conduct their important job of tending brood and the queen. Queens infected with Nosema have shortened lives and lay fewer eggs.
Moving bees rapidly from one cropping system to another places additional demands on colonies. Crops grown in different parts of the country such as apples, peaches, melons, peppers, cherries, almonds, and blueberries depend on honeybees and native bees for pollination. With most feral colonies of bees extirpated by mites, and ever declining numbers of hobbyist beekeepers, the loss commercial honeybee colonies is significant and places extreme demands on remaining hives to complete the important job of pollinating our crops. Later this spring, scientists will complete another survey with beekeepers and we will learn what happened with honey bees and CCD last year. Early reports have it that this long chilly winter will not prove to be a good one for our honeybees.
Bug of the Week thanks Dr. Jeff Pettis of the USDA Honeybee Research Lab for providing inspiration and information used in this episode. “Preliminary Results: A Survey of Honey Bee Colonies Losses in the U.S. Between September 2008 and April 2009” by Dennis vanEngelsdorp, Jerry Hayes, and Jeff Pettis was used as a reference for this episode. To learn more about honey bees and the latest on CCD, please visit the following web site.