Researchers from North Carolina State University have found that honey bees self-medicate when their colony is infected with a harmful fungus. The bees bring in increased amounts of antifungal plant resins to ward off the pathogen. The bees line their hives with increased propolis -- a waxy, yellow substance pictured above. Propolis is a combination of plant resins and wax that has antifungal and antibacterial properties.
Dr. Michael Simone-Finstrom, a postdoctoral research scholar in NC State's Department of Entomology and lead author of the study, says, "The colony is willing to expend the energy and effort of its worker bees to collect these resin. So, clearly this behavior has evolved because the benefit to the colony exceeds the cost."
Researchers found that, when faced with a fungal threat, bees bring in significantly more propolis – 45% more, on average. The bees also physically removed infected larvae that had been parasitized by the fungus and were being used to create fungal spores. Researchers know propolis is an effective antifungal agent because they lined some hives with a propolis extract and found that the extract significantly reduced the rate of infection.
The researchers also found that the honey bees can sometimes distinguish harmful fungi from harmless ones, since colonies did not bring in increased amounts of propolis when infected with harmless fungal species. Instead, the colonies relied on physically removing the spores.
The researchers also say that domestic beekeepers avoiding colonies using propolis may be making a mistake. Dr. Simone-Finstrom says, "Historically, U.S. beekeepers preferred colonies that used less of this resin, because it is sticky and can be difficult to work with. Now we know that this is a characteristic worth promoting, because it seems to offer the bees some natural defense."
The research was published here
in PLoS One.
Photo: Michael Simone-Finstrom, North Carolina State University