Brood removal influences fall of Varroa destructor in honey bee colonies

The hygienic removal of Apis mellifera brood infested with Varroa destructor disrupts the reproduction of the infesting mites, and exposes the foundress mites to potential removal from the colony by grooming. Using brood deliberately infested with marked mites, we investigated the association between the removal of mite-infested brood and the removal of exposed foundress mites in Italian (IHB) and Russian honey bee (RHB) colonies. Our results showed that RHB colonies removed more mite-infested brood in significantly less time (average = 87.9 ± 2.0% for 2.6 ± 0.1 days) than IHB colonies (average = 61.9 ± 7.3% for 3.2 ± 0.1 days or 19.3% per day). For the inoculated brood that was not removed, RHB colonies had lower proportions of brood cells containing: (a) live marked mites regardless of reproductive status (RHB = 4.4 ± 1.3%; IHB = 17.7 ± 5.9%); (b) dead marked mites (RHB = 1.1 ± 0.5%; IHB = 7.1 ± 2.2%); (c) lost introduced marked mites (RHB = 6.6 ± 1.6%; IHB = 13.3 ± 2.8%); and (d) reproductive marked mi...