Fly Parasite in Honey Bee? A New Threat?

The news that flashed across the Internet today indicates there's a new threat to honey bees, a parasitic phorid fly.

UC San Francisco researchers, in an article published today in the Public Library of Science (PLoS One), wrote in their abstract: "Honey bee colonies are subject to numerous pathogens and parasites. Interaction among multiple pathogens and parasites is the proposed cause for Colony Collapse Disorder (CCD), a syndrome characterized by worker bees abandoning their hive. Here we provide the first documentation that the phorid fly Apocephalus borealis, previously known to parasitize bumble bees, also infects and eventually kills honey bees and may pose an emerging threat to North American apiculture. Parasitized honey bees show hive abandonment behavior, leaving their hives at night and dying shortly thereafter."

Should beekeepers be worried? Should they lose any sleep over this?

Noted honey bee expert, Extension apiculturist Eric Mussen of the UC Davis Department of Entomology, says "no"--at least not on the level of fly parasitism actually causing CCD or great losses.

Mussen, who was not involved in the study, says that the scientific paper "explains why some infested, honey bee adults leave the colony at night and are not likely to come back.  The percent infestation level is not high enough to cause a CCD loss by itself."

Mussen attributes CCD to a suppressed immune system, probably caused by a combination of factors such as pests, parasites, pesticides, diseases, malnutrition, and stress. The fly does not appear to be a dominant factor.

However, as Mussen told Erik Stokstad in today's Science article,"Parasitic Fly Dooms Bees to Death by Maggots: "Anything that further stresses the bee population and increases bee losses can contribute to CCD."

The key word is "contribute." The fly may be "contributing" to the loss of adult bees from colonies, but that is probably also happening in colonies that are NOT collapsing, Mussen points out.

"How likely is it that colonies will succumb to this new threat of fly infestations?" we asked Mussen today after a host of articles appeared on the Internet.

Indeed, some news reports describe the infected bee as a "zombie bee."

"If the colony is shrinking abnormally, the bees often can re-establish the normal size by rearing 'extra' brood," Mussen told us. "However, depending upon the inherent genetic abilities of a specific colony to tolerate fly parasitism, some colonies might be prone to developing parasite levels that are overwhelming, and actually succumb to the infestations."

Honey bees, Mussen said, have "an amazing ability to make up for" unanticipated losses--like exposures to bee-toxic agrichemicals in the fields--to the adult population by rearing more brood than would be expected at that time of the year to return to normal populations size.

Mussen will discuss threats to the honey bee when he delivers the keynote speech, "Never Expect 'Business as Usual'" at the 43rd annual American Honey Producers' Association Convention, set Jan. 4-8 in Phoenix, Ariz.

Bottom line: The current U.S. environment seems to be very stressful to honey bees, with or without the parasitic florid fly.

This fly appears to be another ointment in a bee's ill health.