For decades, Australia was the last inhabited continent free of the bee-killing Varroa mite (Varroa destructor).
Authors
- Casey C. Forster
Postdoctoral Researcher, School of Natural Sciences, Macquarie University
- Théotime Colin
Postdoctoral Researcher, Bee Ecology, Macquarie University
That all changed in June 2022, when Varroa was detected near Newcastle and rapidly spread along the coast of eastern Australia. By September 2023, authorities had abandoned attempts to completely eradicate the tiny parasite.
So Varroa is here to stay. For beekeepers across Australia, that means learning to live with the risks of infested hives, lower production and lost income .
So, how are we currently managing Varroa? And what needs to change?
A deadly mite
The Varroa mite is a tiny parasite that attaches to honeybees and feeds on them, impairing their development, immunity and behaviour. These mites can also carry various bee-killing pathogens .
Varroa mites can wipe out entire colonies if left untreated . For this reason, they are considered the foremost threat to managed honeybee colonies worldwide.
Varroa can rapidly spread through human intervention , such as when a person moves infested hives or equipment between two sites. But these mites largely jump between hives through normal bee activities including " drifting ", where confused bees enter the wrong hive. " Robbing ", where bees from a strong colony plunder a weaker one for resources, is another common way Varroa spreads.
Australia's response
In Australia, authorities have sought to bolster the industry and slow Varroa's spread under a national management program , introduced in early 2024. Today, the scale of the problem varies from state to state.
Queensland , New South Wales and the Australian Capital Territory now have well-established Varroa populations. In these states, local apiarists have largely shifted to routine management, which involves regularly monitoring and managing mite levels through various treatments.
Varroa has been detected in multiple parts of Victoria and South Australia . However, both states are on high alert and are bracing for more widespread infestations this spring.
Western Australia , Tasmania and the Northern Territory are currently free of Varroa. To stay that way, they are strengthening early detection and border monitoring efforts.
How do we currently treat Varroa?
Effective Varroa management relies on three key principles.
1. Monitoring
Regular monitoring typically involves taking about 300 bees from a hive and washing them in alcohol or soapy water. This process kills the bees, but is a small and necessary sacrifice. It allows beekeepers to identify and count any mites, before deciding whether further treatment is needed.
2. Treatment
Varroa treatments can be costly and complicated. Finding miticides - a type of pesticide specifically designed to kill ticks and mites - that are toxic to the mite but do not harm bees is a tough task. Current chemical treatments can harm bees by reducing adult and brood survival or impairing how well adults function.
Some miticides can't be used above certain temperatures or during nectar flows - the period when local plants bloom and produce lots of nectar. Most worryingly, Varroa mites can quickly become miticide-resistant. In the past three years, mites in most states have developed resistance to pyrethroid- and formamidine-based treatments.
Due to these limitations, many apiarists might view chemical treatment as a last resort and may first turn to chemical-free or biotechnical approaches . Biotechnical strategies disrupt the mites' reproductive cycle by interrupting the production of bee brood - the eggs and larvae of honeybees - or trapping mites to be physically removed. However, many traditional biotechnical approaches require time and experience and may hamper the growth of the bee colony.
3. Post-treatment
Beekeepers can slow the spread of Varroa by keeping colonies well fed to prevent robbing. To reduce drifting , apiarists can also place hives further apart and face hive entrances in different directions.
Backing our beekeepers
We can better support our beekeepers by:
offering training and mentorship opportunities to help them share Varroa management knowledge and skills
splitting or donating colonies to apiarists who have lost hives
listening to industry-level concerns about the economic and operational pressures commercial beekeepers face and consider providing financial support, such as covering the costs of ongoing treatment and travel during pollination season
protecting and restoring forests to provide bees nectar and pollen.
Without support, the Australian Honeybee Council estimates almost 40% of commercial beekeepers will leave the sector in the coming years. This means there will be fewer bees pollinating crops - putting our farming communities and food security at risk.
Where to from here
Current Varroa management guidelines are largely based on data from other countries . So we urgently need more research to understand which management strategies work best in Australian conditions. We should also investigate ways to make biotechnical methods faster and easier to use.
There's no silver bullet in the fight against Varroa. But in Australia, we have the benefit of time. As the world's last major honey-producing country to detect Varroa, we can draw on three decades of global expertise and tailor strategies to our conditions. The future of our bees and beekeepers depends on it.
Casey C. Forster receives funding from the Ian and Shirley Norman Foundation. She is affiliated with the New South Wales Apiarists' Association.
Théotime Colin receives funding from the Ian and Shirley Norman Foundation and the Australian Research Council Early Career Industry Fellowship. He is affiliated with the New South Wales Apiarists' Association.
