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