EN
A complete loss or decrease of varroacid efficacy of Apistan (tau-fluvalinate) has been stated in some Mediterranean and Austrian regions. The results of studies on this problem presented at the 34-th International Congress of Apimondia in Lausanne - 1995 poited to the development of Varroa jacobsoni mites resistant to Tau-fluvalinate and other acaracid pyrethroids. Since tau-fluvalinate has been used in Poland for a number of years, the development of V. jacobsoni resistance to this preparate cannot be neglected. The efficacy of Fluvarol (tau-fluvalinate) in relation to the multiplicity of its application has been examined. The examinations were done in the honey bee colonies (the Bielsko-Biała region) treated with tau-fluvalinate four times in 1991-94 or twice in 1993-94. Un treated colonies served as a control. The efficacy (66.4%) after four applications tau-fluvalinate points to the development of V. jacobsoni strains resistans to this chemical.