New PCR–RFLP diagnostics methodology for detecting Varroa destructor resistant to synthetic pyrethroids

A significant share of the current seasonal losses of honey bee colonies can be attributed to the ectoparasitic mite Varroa destructor. Its direct feeding behaviour and virus vectoring decimate the colony until collapse if there is no effective control management in place. The synthetic pyrethroids such as tau-fluvalinate and flumethrin were intensively used to control the mite until multiple cases of resistance were reported since the early 1990s. Previous studies have shown that there are three different mutations at amino acid position 925 (L925V, I and M) of the V. destructor voltage-gated sodium channel associated with the resistance to these compounds. Here, we report the development of a new PCR–RFLP methodology to discriminate between susceptible and pyrethroid-resistant Varroa destructor mites. This is a DNA-based assay that proved to be as accurate and robust as the previously reported TaqMan®-based high-throughput genotyping assays but significantly cheaper and more accessible to low-resourced laboratories. It is also easier to identify resistant mites using the new assay. The beekeeping community will surely welcome this new technology since there are very few effective acaricides to deal with the mite. They are aware that pyrethroids can be very effective in absence of resistance so having the possibility to use them as alternative to other compounds as part of an integrated management strategy would be of great help for long-term controlling of the parasite.