Introduction: The mite Varroa destructor is one of the major threats to the western honey bee (Apis mellifera). Formic acid is an effective drug against this parasite. Due to its numerous advantages over synthetically produced drugs, the organic acid is a widely used and popular antiparasitic by beekeepers. Aim: The aim of this work is to present the efficacy and side effects of Varroa treatment with 60% formic acid in honey bees and to investigate the associated effects on honey bee behaviour. Materials and methods: The efficacy and side effects of a varroa treatment with 60 % formic acid in different evaporator systems were investigated at the Kirchhain Bee Institute. For this purpose, 48 double colonies were treated at two locations with different evaporators and dosages. Statistical analysis was performed using a general linear model (GLM) and Sidak post hoc tests for pairwise comparisons (SPSS 26.0), as well as an analysis of variance