Agricultural
16 February, 2026
Authorities confirm first case of Varroa mite pyrethroid resistance
Laboratory testing at the Elizabeth Macarthur Agricultural Institute identified a known genetic mutation, L925I, which causes pyrethroid resistance in Varroa mites.
NSW Department of Primary Industries and Regional Development (DPIRD) has confirmed the first case of Varroa mite pyrethroid resistance in the state and says best practice mite management is now more important than ever.
DPIRD Honey Bee Technical Specialist, Elizabeth Frost, said L925I significantly reduces the efficacy of pyrethroid miticides in managing affected mite populations, with just two approved pyrethroid miticide active ingredients available in Australia, flumethrin and tau-fluvalinate (sold as Bayvarol and Apistan).
“The resistant mites were collected from Northern NSW flumethrin-treated bee colonies where the mid-treatment inspection revealed poor treatment efficacy in the hives and dead colonies,” Ms Frost said.
DPIRD Senior Bee Biosecurity Officer, Rod Bourke, said best practice mite management is now more important than ever for beekeepers managing hives with Varroa.
“Beekeepers can use the Varroa management tool, rotate chemical modes of action (MOA) and follow the label and permit conditions,” Mr Bourke said.
“Check mite loads two to three weeks after treatments have been added and when removed so you can monitor treatment efficacy and the risk of pyrethroid resistant mites in your apiaries or region. If a product does not appear to work, you may need to try the next suitable miticide with a different MOA otherwise mites will harm the colony further.
“Pyrethroid-based miticides remain an important part of integrated pest management for Varroa mite and avoiding back-to-back treatments with pyrethroids is critical in preserving their effectiveness.”
NSW DPIRD staff will work with beekeepers to assess the situation and assist in screening mites for resistance, if needed.
Screening has also shown the pyrethroid resistant mites carried endemic viruses already established in Australia with no exotic viruses.
Testing to date indicates that the resistance is unlikely to be associated with a new Varroa mite incursion.
Distribution of resistant mites is likely to be isolated to a small area at this stage and bee biosecurity officers are surveying Varroa mites across NSW to get a better idea of the distribution of resistant mites.
