Bug of the Week March 23, 2009

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A week or so ago a colleague called and asked what kind of insects would be pollinating trees and shrubs like witch hazel, winter daphne, and other hibernal bloomers. I gave a standard answer that a few pollinators, notably flies and perhaps some beetles might be active on a warm winter day. Last week on a warm afternoon I conducted a “reality – check” on this notion and visited a small and remarkably fragrant patch of Winter Daphne in my backyard. I was delighted to discover several honey bees busily collecting pollen and slurping nectar from the blossoms. As there are no commercial beekeepers in my neighborhood and a bee box is nary to be seen in any backyard in my town, I am hopeful that somewhere in the woods a hollow tree serves as home for a feral colony of honeybees. Bee trees were rather common in northeastern forests and woodlots back in the day when I was a kid until the introduction of varroa mites in the late 1980’s. Varroa mites infest honeybees and suck blood from larvae, pupae, and adults, particularly male bees. Not surprisingly, this weakens bees and predisposes them to 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. 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 honey bee 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. Bees are estimated to pollinate more than 80% of fruits and vegetables worldwide. In the United States, services provided by honey bees are valued at more than 14 billion dollars annually. Between September 2006 and March 2007, beekeepers lost approximately 31% on their beehives. In the same period in 2007 and 2008, beekeepers lost about 35% of colonies and of all losses 10% was attributable to CCD. While this may not sound like much, of the 2.5 million colonies in the United States, 1.5 million are needed to pollinate almonds alone. Many other crops such as apples, peaches, melons, peppers, cherries, and blueberries depend on honeybees and native bees for pollination. The loss of 10% of all commercial honey bee colonies is significant and places extreme demands on remaining hives to complete the important job of pollinating our crops. The cause of CCD is not fully understood, but researchers have made great progress identifying some of the culprits in this mystery. 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 bee 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. High demands for pollinators to rapidly move from one cropping system to another place additional demand on bees. For example, bees may be shipped from Florida where they have been used to pollinate citrus to California for the almond crop. The next stop may be Washington State to pollinate apples or Michigan for the blueberry crop. The extent to which transit affects bees and CCD is not fully known, but it does not appear to be a major factor in the development of the disorder at this point in time. In the next several week scientists will complete another survey with beekeepers and we will learn what happened with honey bees and CCD last year. Perhaps, a HBSP – honey bee stimulus package - should be approved to help our dependable and beleaguered friends.

Bug of the Week thanks Adrian Higgins and Susan Reimer for providing the inspiration for this episode. We are extremely grateful to Dr. Jeff Pettis of the USDA Honeybee Research Lab for taking time to share his thoughts and wisdom about CCD. Articles used in the preparation of this episode include “Pesticide residues in beeswax samples collected from honey bee colonies (Apis mellifera L.) in France” by Marie-Pierre Chauzat and Jean-Paul Faucon and “Assessment of Pesticide Residues in Honey Samples from Portugal and Spain” by Christina Blasco, Mónica Fernández, Angelina Pena, Celeste Lino, Ma Irene Silveira, Guillermina Font, and Yolanda Picó. Several great references were consulted at the Mid-Atlantic Apiculture Research and Extension Consortium.
To learn more about honey bees and CCD, please visit the Mid-Atlantic Apiculture Research and Extension Consortium web site and Susan Reimer’s blog.

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