Fungal problems and pathogens are one of the fastest growing threats to bees and other animals in the world and protection from these problems exercises all of our minds from worrying about mould on the curtains to internal and external fungal infections in our bodies. Now research has shown that for a threat, there is a cure. In what is really a superb demonstration of the power of nature to protect and heal some new research shows that honey bees “self-medicate” when their colony is infected with a harmful fungus, bringing in increased amounts of antifungal plant resins to ward off the pathogen.
Dr. Michael Simone-Finstrom, a postdoctoral research scholar in NC State’s Department of Entomology and lead author of a paper describing the research said, “so clearly this behaviour has evolved because the benefit to the colony exceeds the cost. The colony is willing to expend the energy and effort of its worker bees to collect these resins.”
Honey bees normally line their hives with propolis, a mixture of plant resins and wax that has antifungal and antibacterial properties and beekeepers will have seen hive bees also use propolis, to fill in cracks in their hives and to varnish the wooden walls. However, researchers found that, when faced with a fungal threat, bees bring in significantly more propolis — 45 percent 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.
The researchers know that 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. They also found that 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.
However, the self-medicating behaviour does have limits. Honey bee colonies infected with pathogenic bacteria did not bring in significantly more propolis — despite the fact that the propolis also has antibacterial properties. There was a slight increase, but it was not statistically significant.
There may be lessons to learn here for beekeepers. Historically beekeepers preferred colonies that used less propolis because it can be difficult to work with and sticks everything together. I have been known to bend a hive tool trying to separate boxes on occasion. Now we know that this is a characteristic worth promoting, because it seems to offer the bees some natural defence.”
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