Acaricidal effect of oxalic acid in honeybee (Apis mellifera) colonies

Abstract

Three oxalic acid (OA) solutions were applied to 24 honeybee colonies to test acaricidal effects on Varroa destructor. Daily natural mite drop per colony averaged 0.52. Higher mite mortality (18.33) was found after three August OA treatments. The mean efficacy's of the three water solutions of OA/sucrose (w/w), 3.4%/47.6%, 3.7%/26.1%, and 2.9%/31.9% applied in the presence of brood, was 52.28%, 40.66% and 39.16% respectively. A significantly higher efficacy was recorded when 3.4%/47.6% was applied in comparison to 2.9%/31.9% solution. There was no difference in efficacy between OA solutions administered during a broodless period on October 28. The average efficacy in all colonies was 99.44%. The results suggest that OA has limited acaricidal effect in colonies with brood, but it is highly effective in a broodless period.