Colonies infected with Ascophaera apis collect more propolis. Colonies experimentally enriched with propolis had decreased infection intensities of this fungal parasite Increased resin collection after parasite challenge: a case of self-medication in honey bees?,
PLoS ONE
, Volume 7, Number 3, p.e34601, (2012)
[1].
See also:
http://www.sciencedaily.com/releases/2012/03/120330111027.htm