Pyrethroid resistance In Varroa mites
What Victorian beekeepers need to know
Varroa resistance to pyrethroid chemical treatments confirmed
In January 2026 the first case of Varroa mite (Varroa destructor) pyrethroid resistance was confirmed in a small number of apiaries in New South Wales following treatments not reducing mite numbers as expected.
Genetic testing identified a single mutation in these Varroa mites, L925I. This mutation significantly reduces the efficacy of pyrethroid treatments in controlling affected mite populations.
There are 2 approved pyrethroid miticide treatments available in Australia – flumethrin (sold as Bayvarol) and tau-fluvalinate (sold as Apistan).
The distribution of pyrethroid-resistant Varroa is likely to be limited at this stage but may spread over time.
Miticide resistance
Miticide resistance happens when some Varroa mites naturally have small genetic differences that help them survive a chemical treatment that would normally kill them. The L925I mutation that can make Varroa resistant to pyrethroid chemical treatments is an example of this.
If the same chemical is used again and again for too long or in the wrong way, the mites that survive and reproduce will be resistant to that chemical and pass that resistance to their offspring.
Over time, more mites in the population become resistant and the treatment becomes less effective – or may stop working altogether.
What this means for beekeepers
Once Varroa mites develop resistance to a particular chemical treatment it may become less effective or no longer work at all.
If mites in Australia develop resistance to one or more chemical treatments, that means losing important tools in controlling Varroa populations.
Fewer effective treatment options can make it harder and more expensive to manage Varroa mite in your apiary, potentially leading to higher mite levels in hives, increasing colony stress and colony losses.
What is being done about the resistance
NSW Government (Department of Primary Industries and Regional Development) is leading the response on this issue, conducting further surveillance and testing to determine the spread of resistance.
Testing of the resistant mites is underway to try to understand whether the mutation:
- was already in Australia but only recently detected now that varroa is becoming widespread across the eastern states of Australia
- happened because of the overuse of pyrethroid chemical treatments
- came from a new group of mites brought into Australia via illegal importation.
States, territories and the Australian Government continue to work with industry around Varroa mite, through the National Bee Biosecurity Program and National Bee Pest Surveillance Program.
What beekeepers should do
Beekeepers can take key steps to protect their hives, slow the spread of this resistance and prevent Varroa becoming resistant to the remaining available chemical treatments.
Combine monitoring, cultural/mechanical controls and chemical treatments only when needed.
Test your hives regularly and apply chemical treatments only when treatment thresholds are met, instead of using a fixed schedule.
In Australia, it is critical to only use chemicals that have been registered or granted an emergency permit by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for the control of Varroa destructor. Using unapproved ‘home brew’ or overseas products is illegal, risks harming your bees and can contaminate honey with residues.
Information on legal available chemical treatments can be found at Varroa chemical control options (National Varroa Mite Management Program)
Alternate between different types of chemical treatments with different modes of action so mites are not repeatedly exposed to the same active ingredient.
Proper dosage and treatment duration are essential. Using miticides incorrectly can accelerate resistance in the Varroa population.
By documenting the product used, dates of application, and before and after-treatment mite counts, beekeepers can identify when a treatment is no longer effective, signalling a potential build-up of resistance in the mite population within your apiary.
Stay up to date on the latest research and management practices to protect your hives from Varroa mite infestations and ensure the ongoing health of the colonies.
Report treatment failures
Don’t hesitate to report any suspected cases of treatment failure: contact the Exotic Plant Pest Hotline on 1800 084 881.
For more information
Beekeepers can access free resources on managing Varroa mites at National Varroa Mite Management Program
For Varroa management advice contact our Victorian Bee Biosecurity Officers on 136 186 or email honeybee.biosecurity@agriculture.vic.gov.au