Widespread pyrethroid resistance in Varroa destructor in Türkiye: a molecular warning

This study examined the prevalence of pyrethroid resistance mutations in Varroa destructor (Anderson and Trueman 2000) populations across ten Turkish provinces, utilizing PCR-RFLP assay. By targeting codon 925 in the voltage-gated sodium channel (vgsc) gene, a recognized site for knockdown resistance (kdr), we identified a notably high frequency of resistant alleles within the field populations. Among the 800 mites analyzed, 83% were homozygous resistant, 14% were heterozygous, and only 3% were susceptible. Regional analysis indicated the highest resistance levels in Eastern Anatolia (94%), followed by Central Anatolia (80%) and Marmara (71%). The widespread fixation of resistance alleles is likely attributable to the excessive and repeated use of flumethrin-treated strips, which exert strong selection pressure. The low heterozygosity rate, observed at only 14%, supports the hypothesis of directional selection and potential genetic bottlenecks in these populations. These findings are consistent with patterns reported in other Mediterranean countries, indicating a broader regional trend. Overall, this study presents comprehensive and concerning data on the resistance of Turkish Varroa populations, reinforcing global calls for sustainable and adaptive mite management strategies and providing a valuable reference for policymakers and beekeepers.