Experiments were conducted in three apiaries to assess the comparative efficacy of: Thymovar (Andermatt BioVet AG); Apiguard (Vita Europe Ltd., UK); an oxalic acid solution (OA) which consisted of 2.9% oxalic acid and 31.9% sugar in water; and amitraz fumigation, for controlling the honey bee mite Varroa destructor. Mite mortality increased significantly (p<0.001) in the Thymovar, Apiguard, OA or amitraz treated colonies. The relative mite mortality after: four OA applications, two Thymovar or two Apiguard applications during August and September in the Senično apiary was 41.80% (±14.31), 14.35% (±10.71), and 18.93% (±13.56), respectively. In the control, i.e. untreated colonies, the mite natural mortality was reduced by 3.10% (±3.50). In the Bohinj apiary, two Apiguard applications and a single amitraz treatment resulted in reducing the mite populations by 19.71% (±12.61) and 23.89% (±14.25), respectively. At the Mediterranean located apiary of Vipava, the Thymovar and Apiguard treatments trigged 59.02% (±17.28) and 46.50% (±13.33) of the total mite reduction. In the Vipava apiary, colonies treated with any miticide during the brood period presented no difference (P>0.05) in efficacy. The results indicate that OA, Thymovar, Apiguard or amitraz fumigations are of limited use during the brood periods.
