How resistant to fluvalinate are Varroa populations in Portugal

The varroa mite (Varroa destructor) was first detected in Portugal in 1986. Since then, there has been a widespread use of fluvalinate (Apistan, Klartan) in the attempt to cope with it. Following (i) various credible international reports of increased varroa resistance to fluvalinate and (ii) repeated claims from national beekeepers of poor efficacy of Apistan treatments, a large screening project was setup (2003/2004) for trying to identify honey bee colonies hosting varroa populations resistant to fluvalinate in continental Portugal. As a first step, approximately 1200 beekeepers were enquired nationwide, with a view to building up a rank of apiary-specific probability indexes of varroa resistance to fluvalinate. From those beekeepers, approximately 4.000 colonies were field-tested according to the “British National Bee Unit” field testing methodology, and compared to blank control tests (same kits and methodology, but without using fluvalinate). From those investigated colonies, 1536 allowed conclusive testing (i.e. where 3 or more varroa per honey bee colony were submitted to the action of fluvalinate). Approximately 57 % (878) of these colonies were considered to host varroa populations resistant to fluvalinate (using, as border line, 60 % of fluvalinate induced varroa mortality). Furthermore, it is alarming that the therapeutic efficacy of fluvalinate in the field tests carried out on those 878 colonies only reached an average of 26.4 % (s.e.m. = 0.6 %). Brood samples were later collected for laboratory reassessment of populations of varroa that had been flagged, by the field tests, as resistant to fluvalinate. In most cases,the laboratory tests confirmed the results the field tests had suggested

Fluvalinato; Varroa; Abelhas; Portugal / Fluvalinate; Varroa; Honey Bees; Portugal.