Varroa Mite On Honey Bee Pupa Photo: CSIRO
Varroa mite is a parasite of honey bees that has been inadvertantly spread worldwide. Its introduction into the US in 1989 and the UK in 1992 was shortly followed by a decline in the feral (unmanaged) bee population. The Varroa mite harms bees by direct feeding on their fluids. It harms bees indirectly by transmitting Deformed Wing Virus. Prior to the introduction of Varroa, DWV was a minor occurrence. In addition to wing deformities, DMV cause behavioral changes that stress bee colonies. Some estimates put overwinter colony loss to DWV at around 70%. Anecdotal reports of an uptick in feral bee colonies in the UK, led a group of scientists* to investigate the feral colonies for susceptibility to Varroa mite. They asked the question, could the uptick in feral colonies due to resistance to Varroa? If so, that trait might be bred into domestic honey bee colonies.
No luck. They found that feral populations had even higher incidence of DWV than managed populations. This suggests that management of Varroa mites is effective in reducing disease. However, the anecdotal increase in feral colonies does not appear to involve resistance to Varroa. Varroa remains a vexing problem in need of better solutions.
Parasite Pressures on Feral Honey Bees. Catherine E. Thompson, Jacobus C. Biesmeijer, Theodore R. Allnutt, Stéphane Pietravalle & Giles E. Budge. PLoS One. August 15, 2014.