Effect of the Combined Use of Postbiotics and Oxalic Acid Against Varroa destructor Under Field Conditions

Varroa destructor is a parasitic mite of honeybees that is considered one of the main problems in beekeeping today. The reduction in the efficacy of conventional miticides and the presence of residues in beehives highlight the need to investigate new organic products as alternative treatments. Postbiotic products have been shown to decrease mite viability in in vitro experiments. However, their use in beehives has not yet been assessed. The aim of this study was to test the efficacy of postbiotics and oxalic acid against V. destructor under field conditions. Two experiments were performed during the summer and autumn seasons, with four study groups: control (C), postbiotic (POS), oxalic acid (OX), and both combined (POX). Phoretic and brood V. destructor were determined at the beginning and end of the study to assess their evolution, as well as the percentage effectiveness of each treatment by registering the mite fall in beehive sanitary bottoms. Postbiotic alone did not show a significant effect on V. destructor under field conditions. However, the combined treatment of postbiotics and oxalic acid improved the results obtained with oxalic acid alone, resulting in greater effectiveness and reduction of phoretic and brood V. destructor .