First record of resistance to flumethrin in a varroa population from Uruguay

Varroa destructor is the most serious parasitic mite that infests the honey bee Apis mellifera. Different treatments with systemic acaricides are applied to control, but due to the intensive use of these chemicals, resistance to organophosphates and pyrethroids has developed worldwide. Most of the resistance episodes have been registered for fluvalinate, and only in a few cases has flumethrin resistance been reported. In Uruguay, no studies on V. destructor resistance to flumethrin have yet been recorded. High infestation levels of V. destructor are continuously detected in colonies of A. mellifera after treatments with flumethrin. Hence, this study aimed to estimate the possible resistance to flumethrin of a V. destructor population from the Colonia Department. Furthermore, the LC50 baseline levels for flumethrin in two Uruguayan populations were determinated. The LC50 for flumethrin for the population from Colonia Department was 3.8 μg/Petri dish, which means an increase of 34.5 fold when compared to th...