Ineffectiveness of Apistan tretement against the mite Varroa jacobsoni Oud. in several districts of Lombardy (Italy)

The effectiveness of Apistan\uae (Sandoz) was tested in 8 apiaries (78 colonies) in some districts of Lombardy (north Italy) during 1993. The strips were left for 22 d in colonies in which the queens were caged inside the hives. On the 24th day, a treatment with 5 ml/comb of Perizin\uae was given. The fallen mites were recorded every 8 d during Apistan\uae treatment and 2 d after Perizin\uae. The treatment's average effectiveness varied greatly from apiary to apiary (min 4%, max 89.5%). In Lombardy, where quite a high mortality of colonies (caused by varroosis) was reported by some beekeepers during autumn 1992, the average effectiveness of the treatment with Apistan\uae was 44.5%. The results indicate different levels of resistance of Varroa jacobsoni to fluvalinate