Pires, SanciaMurilhas, AntónioMaia, MiguelPereira, Óscar2011-07-012011-07-012007Pires, Sância; Murilhas, António; Maia, Miguel; Pereira, Óscar (2007). Fluvalinate-tolerant varroa populations rapidly loose their lead against apistan. In 40th Apimondia International Apicultural Congress. Melbournehttp://hdl.handle.net/10198/5664Since the early nineties, many Portuguese beekeepers have intensively used various ways of applying fluvalinate into their honey bee colonies. This behavior has imposed a strong selection pressure towards fluvalinate-tolerant Varroa populations, some of which were recently identified in a nationwide study (via fie ld and laboratory testing). Being able to locate such populations opened up the possibility to challenge them against rightly applied Apistan field treatments, as well as to estimate how promptly those populations move back to normal levels of susceptibility to this acaricide.engconference object