<i>Varroa destructor</i> in Portugal: an exploratory assessment of pyrethroids resistance status

The drastic and abrupt loss of honey bee colonies around the world has long unsettled the beekeeping community, and although the phenomenon is far from being solved, there is a relative consensus regarding the detrimental effect the mite <i>Varroa destructor</i> exerts over <i>Apis mellifera</i> populations. In Portugal, this parasite was first recorded in the late 1980s and since then, the beekeepers’ method of choice for controlling the mite are synthetic acaricides, most notably the pyrethroids tau-fluvalinate and flumethrin. Unsurprisingly, resistance to these active ingredients quickly surfaced. Here, we report the first PCR-RFLP resistance assessment in Portuguese apiaries, where 96 <i>V. destructor</i> mites, from different geographic regions, were genotyped between April and August of 2019. The results showed that 47% of the sampled mites exhibit the mutation correlated with resistance. These findings stress the need for a current characterization of the acaricides being used and a description of how the treatments are been applied.