Mussen, emphasizing he does not see the phorids as a major threat, said that perhaps “all the other stresses that we have been studying have combined to impair the immune system of the bees.  Then, whatever mechanism in the bees' bodies that used to prevent successful parasitism by the fly no longer is working as well.  Nearly every facet we have studied--microbes, mite feeding, exposure to pesticides, etc.--all have had a suppressing effect on the honey bee immune system.  The current U.S. environment seems to be very stressful to honey bees.”

Among the other speakers at the Jan. 4-8 convention will be bee breeder-geneticist Susan Cobey, who has a dual appointment at UC Davis and Washington State University. She will discuss “The Introduction of Honey Bee Germplasm and Re-Establishment of Apis Mellifera Caucasica” on Saturday, Jan. 7.

Asked about the phorids, Cobey said she learned a year ago of the San Francisco-based study. “I’m still not sure how widespread it is or how much of a problem it may be…another contributing factor in the (bee health) puzzle.”

Colony collapse disorder (CCD), first noticed in the winter of 2006, is a mysterious malady characterized by worker bees abandoning the hive. Mussen believes it is a combination of factors that suppress the immune system: pests, parasites, pesticides, diseases, malnutrition and stress.

“It’s a complex issue,” he said at a 2007 seminar at UC Davis when he chronicled bee health. “But one thing is certain:  It seems unlikely that we will find a specific, new and different reason for why bees are dying.”

Hive abandonment not a new occurrence, Mussen said at the seminar.  “Similar phenomena have been observed since 1869. It persisted in 1963, 1964 and 1965 and was called Spring Dwindling, Fall Collapse and Autumn Collapse. Then in 1975, it was called Disappearing Disease.  But the disease wasn’t what was disappearing. The bees were.”

Although the cause of CCD is unknown, scientists have noted the high number of viruses and other pathogens, pesticides and parasites present in CCD colonies, as compared to non-CCD colonies. The high levels contribute to weakened immune systems, making the bees more susceptible to pests and pathogens.