Efficacy of oxalic acid and apiguard against Varroa mites in honeybee (Apis mellifera) colonies

Abstract

This trial assessed the comparative efficacy of oxalic acid solution (OA), which consists of 2.9% oxalic acid and 31.9% sugar in water, and Apiguard, a thymol gel, in controlling the honeybee mite Varroa destructor. In comparison with untreated control colonies, mite mortality, which was evaluated throughout the pre- and post-treatment periods, increased significantly (p < 0.001) in both Apiguard and OA treated colonies. The mite mortality after two Apiguard applications, on August 7 and 21, was 41.98% (± 21.59) and was 42.63% (± 25.22) after three OA applications, on August 7, 14 and 21. All applications were given to colonies with brood. Further three OA treatments conducted during October, on previously untreated control colonies, resulted in mite mortality of 87.92 % (± 12.66). However, these levels of mite reduction were insufficient for all colonies to survive the winter. The results indicate that OA and Apiguard are of limited use during periods with brood. The possible use of OA and Apiguard against the varroa mite in honeybee colonies is discussed in this study.