DECREASE IN APISTAN EFFICACY USED AGAINST VARROA DISEASE IN THE HONEYBEE (APIS-MELLIFERA)

Varroa disease is a very serious parasitosis of the bee, which induces important hive losses. Fluvalinate (Apistan(R)) has been one of the most widely used acaricides since 1989. In 1999, 1993 and 1994, ineffective treatments were observed in Italy and then France, and the hypothesis of a resistance was put forward. The therapeutic efficacy of fluvalinate was estimated in experiments performed in 1992, 1993 and 1994. Groups of colonies from different areas were thus treated for 32-34 d with 2 strips placed in contact with the cluster. Mite mortality was checked with fatted detector boards on hive bottom boards. A treatment with amitraz (Anti- Varroa Schering(R)) to determine the residual infestation of adult bees was performed the day following the strip withdrawal. Brood infestation was checked by examination of 100 capped cells, by entire brood hatching in an incubator, and by counting the mites on emerging bees. The results showed a decrease in efficacy in the Italian colonies in which fluvalinate therapeutic efficacy fell to 29.7% in 1994. The dosage of fluvalinate in the strips before and after treatment and their good positioning with regard to the bees did not allow us to incriminate a misuse of Apistan(R) strips. In France, the therapeutic efficacy wilt be examined at the Italian border during an investigation of all apiaries.