Assessment of Resistance of Varroa destructor to Formic and Lactic Acid Treatment-A Systematic Review

Varroa destructor represents one of the most significant pathogens affecting Apis mellifera. A multitude of treatment modalities exist, including those based on pharmaceutical and biotechnological principles. A few years after the first use of synthetic acaricides, Varroa destructor developed resistance to these substances, becoming a significant concern. The present review assesses the potential risk of resistance development to formic and lactic acid. This is performed by evaluating sources in the literature over the past 30 to 40 years following the PRISMA 2020 guidelines. Median annual efficacies are determined and evaluated over time. Independent of pharmaceutical form, mite populations are considered non-resistant for efficacies higher than 70%. After the assessment of outliers for lactic acid, the remaining limited data are insufficient to draw conclusions on resistance. The reported unusually low efficacy values for formic acid can be explained by inadequate evaporation rates and study settings. Notably, for both acids, the findings are limited by a low number of efficacy values, and further, more detailed and standardized studies are needed.