Field Evaluation of Oxalic Acid Vaporisation for Varroa Mite ( <i>Varroa destructor</i> ) Control in European Honey Bees ( <i>Apis mellifera</i> ) Colonies

Abstract Varroa mites ( Varroa destructor ) are a major threat to honey bee health globally. Oxalic acid has gained popularity among beekeepers as a potential varroa mite control agent. This study evaluated the efficacy of oxalic acid vaporisation for managing varroa mites in field conditions in Taiwan. Twenty-four colonies of Italian honey bees ( Apis mellifera ligustica ) were divided into six groups, each consisting of four colonies: a control (no treatment), four treatment groups receiving two, four, six or eight oxalic acid treatments bi-weekly, and a group treated with Flumethrin strips (40 mg flumethrin/strip). Oxalic acid was vaporized at a rate of approximately 2 g per beehive. After thirty-five days, colonies receiving six and eight oxalic acid vaporisations showed significant reductions in varroa mite infestations, by 86% and 97%, respectively. Moreover, significantly higher worker bee mortality was observed in colonies receiving four, six, or eight oxalic acid vaporisations compared to the control. These findings suggest that six or eight oxalic acid (2 g/hive) vaporisations can effectively control varroa mite infestations in honey bees under field conditions, however beekeepers should be aware of potential impacts on worker bee mortality.