Hello Adony,
                I thought that the appearance of fluvalinate resistant
v-mites in Italy was possibly due to the use of weak solutions of
Fluvalinates prepared from Sheep Dip treatments.  Not only were/are the
solutions weak but the diffusion of the chemical from the soaked wooden
strips lasts only a few days.  There is no sustained emission of the
chemical such as occurs with the plastic impregnated strips of Apistan or
Bayvarol.   This would provide the selection pressure needed to produce
generations of increasingly resistant mites.  Classical Darwinism!
 
Regards
 
Glyn Davies, Ashburton, Devon UK