Honey bee colony mortality and productivity with single and dual infestations of parasitic mite species

Colony mortality and productivity were compared between honey bee (Apis mellifera) colonies infested by zero, one or both species of parasitic mites (Acarapis woodi or Varroa destructor). Mortality, bee and mite populations, sealed brood, and stores were monitored for 16 months, beginning in May. By the following March, 5 out of 6 colonies with both mites were dead, but no other colonies died until September, when 3 out of 4 V. destructor colonies were dead. Dually infested colonies initially had more honey stores, but were dead by March. At that point V. destructor colonies had significantly less worker brood, fewer adult bees and more honey than colonies with no mites or tracheal mites (Acarapis woodi). The colonies with tracheal mites ($n = 9$) and no mites ($n = 8$) did not differ in any productivity parameter measured. These results suggest a synergistic interaction between tracheal and V. destructor mites, treatments against tracheal mites should be applied in dually infested colonies, even if tracheal mites alone are not having an impact