Microbiome of honey bees and Varroa mites in New Zealand

The use of pesticides in beehives constitutes an important health issue for honey bees (Apis mellifera). Miticide treatments are not lethal to bees but could still impose significant sublethal costs. This study examined the impacts of amitraz on the bacterial communities of the honey bee gut and Varroa destructor mites. We sequenced and compared gut 16S rRNA composition pre- and post-amitraz treatment. Amitraz did not significantly influence bacterial gut communities in either honey bees or mites during the first six weeks following treatment. The gut bacterial community of bees was mainly dominated by the commonly observed microbiota in bees, which included species in the genera Gilliamella, Snodgrassella, and Frischella. Deformed wing virus (DWV) loads were analysed but were also unaffected by amitraz treatment over the six-week period analysed. The bacterial community of Varroa destructor mites was heavily dominated by Bartonella spp., in contrast to results observed elsewhere. Our results indicating that amitraz does not appear to affect honey bee microbiota should be helpful for beekeepers who rely on this pesticide for mite control.