More than sixty years living with Varroa destructor: a review of acaricide resistance

Varroa destructor is one of the biggest threats to honey bee populations worldwide. Three classes of disparately acting acaricidal compounds are currently used to combat infestations: the pyrethroid insecticides, fluvalinate and flumethrin; the organophospate, coumaphos; and the formamidine, amitraz. Unfortunately, these compounds tend to persist in both honey and wax compromising honey bee health and contaminating hive products used by humans. In addition, overuse of synthetic compounds encourages the emergence of acaricide resistance in V. destructor. Current evidence suggests that resistance to pyrethroid insecticides in V. destructor initially arose in Italy during a four-year period of heavy pyrethroid application. After that, several cases of resistant populations have been reported around the world. More data is needed to track the origin and dispersal of mites resistant to the organophosphate coumaphos, and formamidine amitraz. Little is known about the genetic procedures leading to fixation of acaricide resistance genes, which can vary depending on mite genetics, environmental conditions, and beekeeping management. This review highlights the main aspects associated with the development of acaricide resistance and alternative strategies are suggested to deal with this problematic.