The effects of in-hive miticides on honey bee (Apis mellifera) queen retinue response and mandibular pheromones

Honey bee (Apis mellifera) populations continue to decline in part due to the ectoparasite Varroa destructor, which often causes colonies to collapse and die.  Varroa mites were initially controlled with two in-hive miticides: the organophosphate coumaphos (Checkmite+) and the pyrethroid fluvalinate (Apistan).  Sublethal in-hive levels of these miticides have been shown to cause colony-wide health problems.  In this study, we explored whether the presence of coumaphos and fluvalinate, as well as the currently used in-hive miticide, amitraz (Apivar), in the queen-rearing beeswax environment has an effect on queen attractiveness to workers. We did this by raising queens in miticide-free beeswax or beeswax containing known concentrations of both coumaphos and fluvalinate or amitraz. We measured the size of each queen’s retinue and conducted a cage experiment whereby five-day old workers were exposed to queen mandibular gland extracts from both queen types. Comparisons of both the average worker retinue size per queen type and the average number of workers attracted to mandibular gland extracts showed that queens reared in miticide-free beeswax attracted a significantly larger retinue than queens reared in miticide-laden beeswax. Significance was determined using a matched-pair t-test. Mandibular gland extracts were then examined using a GC/MS analysis to detect differences in the pheromone chemistry of queens in each treatment group. Our results indicate that exposure to miticides during queen development severely alters retinue behavior by impacting the queens’ pheromones, which are what the queens use to attract a retinue. This has important implications regarding the potential synergistic effects of the in-hive miticides on colony health.