Since 2017, the Atlantic Tech Transfer Team for Apiculture has been testing the efficacy of the synthetic miticide Apivar®. The consensus across the Maritime region, and supported through ATTTA’s research, is that Apivar® remains a product with high efficacy for the management of Varroa mites. It is becoming increasingly prevalent how important it is for the Maritime region to maintain the efficacy of Apivar®, as there are continued reports of amitraz (active ingredient of Apivar®) resistance across the globe and within Canada. This week’s blog will highlight new research that demonstrates the prevalence of amitraz resistance is increasing, including proposed mechanisms of resistance.

Status of Amitraz Resistance in Canada

Across the globe, amitraz resistance is becoming increasingly prevalent. Over the past 20 years amitraz-resistant mite populations have been confirmed in the United States^1,3, France^1,2, Spain⁴, Argentina⁵, Mexico⁶, Czech Republic⁷, Portugal⁸, and Algeria⁹. The issue of amitraz-resistance is wide spread, and presents a large threat to the global beekeeping industry.

Within Canada, there have been anecdotal reports of decreasing Apivar® efficacy over the past decade. A recent Canadian study detected reduced Apivar® efficacy in apiaries across Alberta, with product efficacy ranging from 22% to 92%¹⁰, and the majority of included apiaries showing below 55% efficacy. The study also demonstrated that Apivar® efficacy has decreased since 2022, when similar research was conducted in Alberta apiaries¹¹.

Other Canadian provinces do not report reduced efficacy of Apivar®. Previous Canadian studies show high product efficacy of Apivar® (>90%) in Nova Scotia, Prince Edward Island, New Brunswick¹², and Ontario¹³. Additionally, within the Maritime region, the Atlantic Tech Transfer Team for Apiculture has evaluated the efficacy of Apivar® from 2017 to 2024, and has demonstrated that Apivar® is still a product with high efficacy, ranging from 89% to 98%. The team also conducted a study in 2024 that indicates low reduced efficacy of amitraz for a limited number of mites that were assessed from Maritime apiaries using a lab-based methodology. A report was recently publish explaining the methodology, results and conclusions of the mentioned study - https://www.perennia.ca/wp-content/uploads/2025/01/Varroa-Mites-REPORT.pdf.

Current research provides a greater understanding of how amitraz resistance can occur within a population of Varroa mites. Amitraz acts as an octopamine receptor agonist, which means it initiates a physiological response when combined with the receptor. When amitraz combines with the octopamine receptor it causes constant excitation and paralysis of the mite, and causes the mite to drop from the bee’s back¹⁴. Secondarily, mites die due to starvation because of this paralysis¹⁴. Specific genetic mutations within the octopamine receptor, such as N87S and Y215H, have been associated with reduced efficacy of amitraz in Varroa mite populations in both France and the United States^1,3. More recently, in Spain, another mutation (F290L) was found to be associated with reduced efficacy of amitraz in mites⁴. Finally, a study in France, determined that the mutation at position 260, previously a possible mutation related to amitraz resistance, in fact does not directly cause reduced efficacy of amitraz².

The recently published study by Alberta researchers also examined the mechanism of resistance for Varroa mites collected from Alberta apiaries¹⁰. The researchers found that none of the tested mites carried the N87S mutation, but the majority of the sampled mites carried the 2Y15H mutation¹⁰. The study concluded that the mutation Y215H is associated with amitraz resistance, and it is widely distributed across Alberta¹⁰. This is the first study to evaluate the presence and prevalence of mutations associated with amitraz resistance in Canadian beekeeping operations¹⁰.

The Canadian beekeeping industry is at high risk of losing the efficacy of amitraz if integrated pest management is not practiced. Beekeepers should be using a combination of cultural, physical and chemical controls to help manage Varroa mite populations. Beekeepers should be monitoring for mites on a monthly basis, and only providing chemical treatment if the population of mites is at or above the economic threshold. Beekeepers should remember that current established economic thresholds need to be contemplated against the changing climate and lengthening of seasons. Beekeepers should monitor following treatment to know if the product and delivery was effective. Finally, beekeepers should alternate between synthetic and non-synthetic (organic acids and essential oils) to help maintain the efficacy of products such as Apivar®. If you have any question on amitraz reduced efficacy, and/or best management practices for Varroa mites, please reach out to the ATTTA team.

High Varroa mite load shown from alcohol wash (ATTTA©2021).

Connecting with ATTTA Specialists

If you’d like to connect with ATTTA specialists or learn more about our program, you can:

visit our website at https://www.perennia.ca/portfolio-items/honey-bees/

Email attta@perennia.ca

References

1. Hernández-Rodríguez, C.S., Moreno-Martí, S., Almecija, G., Christmon, K., Johnson, J.D., Ventelon, M., Vanengelsdorp, D., Cook, S.C. and González-Cabrera, J., 2022. Resistance to amitraz in the parasitic honey bee mite Varroa destructor is associated with mutations in the β-adrenergic-like octopamine receptor. Journal of Pest Science, pp.1-17.
2. Marsky, U., Rognon, B., Douablin, A., Viry, A., Rodríguez Ramos, M.A. and Hammaidi, A., 2024. Amitraz Resistance in French Varroa Mite Populations—More Complex Than a Single-Nucleotide Polymorphism. Insects, 15(6), p.390.
3. Rinkevich, F.D., Moreno‐Martí, S., Hernández‐Rodríguez, C.S. and González‐Cabrera, J., 2023. Confirmation of the Y215H mutation in the β2‐octopamine receptor in Varroa destructor is associated with contemporary cases of amitraz resistance in the United States. Pest Management Science, 79(8), pp.2840-2845.
4. Hernández‐Rodríguez, C.S., Moreno‐Martí, S., Emilova‐Kirilova, K. and González‐Cabrera, J., 2025. A new mutation in the octopamine receptor associated with amitraz resistance in Varroa destructor. Pest Management Science, 81(1), pp.308-315.
5. Maggi, M.D., Ruffinengo, S.R., Negri, P. and Eguaras, M.J., 2010. Resistance phenomena to amitraz from populations of the ectoparasitic mite Varroa destructor of Argentina. Parasitology research, 107, pp.1189-1192.
6. Rodríguez-Dehaibes, S.R., Otero-Colina, G., Sedas, V.P. and Jiménez, J.A.V., 2005. Resistance to amitraz and flumethrin in Varroa destructor populations from Veracruz, Mexico. Journal of apicultural research, 44(3), pp.124-125.
7. Kamler, M., Nesvorna, M., Stara, J., Erban, T. and Hubert, J., 2016. Comparison of tau-fluvalinate, acrinathrin, and amitraz effects on susceptible and resistant populations of Varroa destructor in a vial test. Experimental and applied acarology, 69, pp.1-9.
8. Pires, S., Murilhas, A., Pereira, Ó. and Maia, M., 2005. Current effectiveness of amitraz against Varroa in Portugal. In Scientific Programme Apimondia Ireland 2005, 39th Apimondia International Apicultural Congress (pp. 78-78). Apimondia.
9. Adjlane, N., 2017. Evaluation of the resistance of the mite Varroa destructor to the amitraz in colonies of honey bees (Apis mellifera) in Algeria. Uludağ Arıcılık Dergisi, 17(1), pp.1-6.
10. Bahreini, R., González-Cabrera, J., Hernández-Rodríguez, C.S., Moreno-Martí, S., Muirhead, S., Labuschagne, R.B. and Rueppell, O., 2025. Arising amitraz and pyrethroids resistance mutations in the ectoparasitic Varroa destructor mite in Canada. Scientific Reports, 15(1), p.1587
11. Bahreini, R., Nasr, M., Docherty, C., Muirhead, S., de Herdt, O. and Feindel, D., 2022. Miticidal activity of fenazaquin and fenpyroximate against Varroa destructor, an ectoparasite of Apis mellifera. Pest Management Science, 78(4), pp.1686-1697.
12. Olmstead, S., Menzies, C., McCallum, R., Glasgow, K. and Cutler, C., 2019. Apivar® and Bayvarol® suppress varroa mites in honey bee colonies in Canadian Maritime Provinces. J Acadia Entomol Soc, 15, pp.46-49.
13. Morfin, N., Rawn, D., Petukhova, T., Kozak, P., Eccles, L., Chaput, J., Pasma, T. and Guzman-Novoa, E., 2022. Surveillance of synthetic acaricide efficacy against Varroa destructor in Ontario, Canada. The Canadian Entomologist, 154(1), p.e17.
14. Chen, A.C., He, H. and Davey, R.B., 2007. Mutations in a putative octopamine receptor gene in amitraz-resistant cattle ticks. Veterinary parasitology, 148(3-4), pp.379-383.