Assessment of Resistance of Varroa destructor to Formic and Lactic Acid Treatment—A Systematic Review
1
Institute of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 43, 04103 Leipzig, Germany
2
Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, Leipzig University, An den Tierkliniken 15, 04103 Leipzig, Germany
*
Author to whom correspondence should be addressed.
Vet. Sci. 2025, 12(2), 144; https://doi.org/10.3390/vetsci12020144
Submission received: 16 December 2024
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Revised: 4 February 2025
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Accepted: 5 February 2025
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Published: 8 February 2025
Simple Summary
Varroa mites (Varroa destructor) are a major pest of honey bees (Apis mellifera L.). Untreated colonies usually die within a few years. Therefore, they must be treated with drugs or biotechnological methods. Varroa destructor became resistant to synthetic drugs within a few years after their first use, which is a substantial problem. This review explores the risk of resistance to formic and lactic acid by looking at the past 30 to 40 years of research. The median annual efficacy is calculated and evaluated over time, considering values of less than 70% a sign of resistance development. There are few data on lactic acid, so a resistance examination is not possible. The reported unusually low efficacy values for formic acid are caused by evaporation rates and study settings, leaving no indication of resistance development. However, the findings are based on only a few efficacy values, so more studies are needed.
Abstract
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.
Keywords:
Varroa destructor; Apis mellifera; resistance; formic acid; lactic acid
