Investigation of resistance against to flumethrin using against Varroa destructor in Türkiye

Abstract

The honeybee ectoparasite Varroa destructor is a major threat to apiculture when evaluating bee diseases and pests. While attempting to control this mite, beekeepers often depend on a small selection of authorized synthetic acaricides, such as flumethrin, which is widely used in Türkiye and globally. However, resistance to flumethrin develops due to incorrect and excessive use. In this study conducted at Ordu Beekeeping Research Institute, trial group were established including an untreated control group and group where flumethrin-based pesticides were applied. Dead varroas collected from pollen traps and live varroas collected from bees were obtained from these trial groups for molecular analysis as positive-negative controls. Varroa samples were collected from provinces representing different regions with intensive beekeeping activities such as Adana, Ankara, Bingöl, Muğla, Ordu, Şanlıurfa, Tekirdağ. Molecular methods were employed to investigate the resistance gene region for pyrethroids (specifically flumethrin) against V. destructor. In our study, individual DNA extractions were performed on dead parasites from colonies subjected to pyrethroid application (resistance negative control) and live parasites (resistance positive control). The DNA samples obtained were used in PCR reactions targeting the region encoding the 925th amino acid of the voltage-gated sodium channel (VGSC) gene, which is responsible for resistance formation. The DNA samples were subjected to gel electrophoresis to observe the amplification products of the expected target region. To examine the nucleotide sequence changes that encode leucine at the 925th amino acid, which is associated with resistance, DNA sequence analysis was applied to the amplification products. Out of 332 V. destructor parasites obtained from different provinces, 279 were analysed using molecular methods. It was observed that 31% of the samples showed sensitivity to flumethrin while 69% exhibited resistance to it. Among the resistant samples: 27% had homozygous isoleucine mutation; 28% had homozygous valine mutation; 2.8% had heterozygous isoleucine mutation; 8.5% had heterozygous valine mutation; and 2.8% had heterozygous methionine mutation, all of which were associated with flumethrin resistance. As a result, the rate of flumethrin resistance in parasites varied between 51% and 94% among different provinces.

Amitraz Resistance in French Varroa Mite Populations—More Complex Than a Single-Nucleotide Polymorphism

“…Likewise, 52.8% of mites carried the homozygous G/G genotype in the group of surviving mites, compared to 71.2% among the perished mites. To determine LC 90 , the results obtained for the two additional apiaries in 2021 were compiled with the results obtained for two other apiaries sampled in 2020, resulting in an estimate of the LC 90 of 25 ppm [CI95: [21][22][23][24][25][26][27][28][29]. The coefficient of determination (R 2 ) obtained was 0.7, which indicates a good prediction of linear regression, and the correlation coefficient (r) was 0.8, indicating a high correlation strength between the variables of acaricide concentration and percentage of mortality effect.…”

“…In several research studies, single-nucleotide polymorphisms (SNPs) were identified as the source of tau-fluvalinate and/or flumethrin resistance in Varroa mites. Although the location of SNPs in the mites’ genome varied geographically, the main target mechanism of the detected variations appeared to be the same: an alteration in the voltage-gated sodium channels, the main target site for pyrethroids [ 20 , 21 , 22 ].…”

“…The topic of the development of resistance against active ingredients of acaricides in Varroa mite populations has received increasing attention in recent years [ 20 , 21 , 22 , 25 ]. There are increasing concerns among beekeepers, veterinarians, bee inspectors, and honey bee health researchers due to an increasing number of reports of amitraz resistance in Varroa mite populations from the field.…”