[PLEASE NOTE: this is a first draft and will evolve over the next few weeks as I complete more research into varroa mite management. Stay tuned!]
In September 2023 the National Management Group announced that Australia would move from the eradication phase to containment and management of Varroa Destructor.
This means that varroa will become endemic within Australia, and particularly quickly within eastern Australia. WA probably has more time to prepare and learn before they are faced with the varroa threat directly.
If you are an Australian beekeeper, you must now learn to manage varroa in your colonies. Unmanaged colonies, including feral colonies, will collapse within 2-5 years. Based on data from New Zealand and the USA, feral colony numbers dropped by 95% within 3 years of those varroa outbreaks. Australia has a particularly high density of feral colonies with estimates of up to 125 colonies per square kilometre. As these colonies succumb to varroa and collapse, they will provide a massive reservoir of varroa to spread into managed hives, so-called "mite bombs".
Worse, though, is the fact that Australian honey bees have never had any exposure to varroa, and as such have little innate resistance. These colonies will initially be overwhelmed by pressure from varroa, weakening the bees and loading them with increased viral pathogens. Without consistent management, these colonies will collapse and die too.
What does varroa management look like?
Managing varroa requires regular testing and recording results of testing over time
Colonies must be tested (alcohol wash) every few months, at least 3 times per year, to determine mite load and pressure on the colony.
This is especially important before colonies prepare for winter. This ensures healthy "winter bees" are raised to sustain the colony through the winter period.
Managing varroa requires scheduled treatments based on testing results and mite loads in colonies
Treatments must be applied to all hives within the apiary, and based on the mite load of the colony/apiary. Leaving hives untreated within an apiary simply leaves a reservoir of mites that will spread to the rest of the apiary following treatment.
Synthetic treatments must be cycled to avoid mite-resistance. Resistance has been observed in other countries due to incorrect application or over-dependence on a single treatment for too long.
Organic acid treatments such as Oxalic and Formic acids are highly effective against mites but have significant health and safety considerations. These treatments are also subject to various environmental conditions rendering them more or less applicable at certain times of year.
Treatment without testing is an ineffective approach as it does nothing to inform the beekeeper about the health of colonies due to impact of mite loads.
Testing, record keeping, and treatment means increased workload and cost for the beekeeper
As beekeepers, we are expected to keep a certain amount of data. With varroa mite management this record-keeping requirement will increase.
Application and removal of treatments will require additional labour. Time == money.
Testing colonies will require additional labour. An alcohol wash takes a about 5 minutes per hive, longer if the colony has supers on, or if finding the queen is required (alcohol washes are destructive, ie kill bees and mites).
Colonies subjected to varroa mite suffer much higher colony losses
Australia traditionally has a very low colony loss rate per year; <5% for well-managed colonies in normal conditions.
Countries similar to Australia, such as New Zealand and the USA, have colony losses approaching or exceeding 50% per year since varroa became endemic
Higher colony loss requires beekeepers to replace stock more often
Buy new hives from suppliers or,
Build and maintain a significant stock of replacement colonies (nucs) within their operation. This adds even more labour, equipment cost, and space requirements for the additional replacement stock needed. Some beekeepers refer to this stock as a "nuc battery" which is used to "recharge" production colony lossess.
Due to more regular brood inspection and destructive testing (alcohol washing), queen loss will become a more significant issue. This will result in more cost and labour required to manage queenlessness in colonies.
What can we learn from the varroa experience in other countries?
New Zealand, the UK, the USA, Canada, and parts of Europe have all been managing varroa for decades. These countries share similar economies, levels of development and governance, and, in places, similar climate zones to parts of Australia. We can learn a lot from the varroa experience of beekeepers and related industries in these countries.
A wide variety of management strategies and treatments have been researched, and applied, with significant lessons learned. Australia would benefit by taking lessons learned from these countries to avoid obvious rookie mistakes on the path to varroa management maturity. Policy settings and management strategies should be informed by these lessons learned.
Education and training of beekeepers is essential
Managing varroa as a common pest is best achieved with an IPM approach. Many beekeepers would be familiar with the concept of IPM, but unfamiliar with the specifics of varroa IPM. The Australian NMG and State bodies should invest heavily in training beekeepers with varroa-specific IPM
Training beekeepers on the manual interventions that help reduce varroa loads in hives and minimise the spread of varroa to other colonies and apiaries.
Testing, record keeping, treatment threshold determination, treatment schedules, and other knowledge is essential to bring our beekeepers up to speed.
"Treatment free" - is it an option in Australia?
Based on what we know today, "treatment free" is not likely to be viable in Australia until stocks of varroa-sensitive bees are built up. Breeding programs are being established to test for VSH bee genetics and to selectively breed more resistant stock, however these programs will take several years and require enormous commitment (ideally from Government and Industry bodies) to ensure VSH stock is readily available.
Without treatment, Australian bees were unable to survive when exposed to varroa in a test in the USA some years ago. They collapsed within months. This is likely to hold for the majority of Australian bee stock as varroa becomes endemic.
Organic treatments
Organic acids (Oxalic and Formic)
Essential Oils
Thymol is an extract from Thyme Oil and is an effective varroa miticide. ApiGuard is a treatment based on Thymol and is commonly used in other countries.
There have been several studies of other essential oils (EOs) that hold promise as miticides. Few studies have been broad enough and few have performed in vivo (in hive) testing, leading to limited conclusions about real-world applicability of these EOs as miticides in active bee colonies.
EOs hold a lot of promise to be both effective miticides and safe, natural treatments that cause little harm to bees and pose no risk to humans (through exposure or consumption).
NOTE: In Australia any treatment must have APVMA approval and must be used as prescribed on the APVMA approval advice. "Off-label" use of any chemical as a treatment in beehives is prohibited and subject to significant penalties. "Chemical" is any substance, even common household "chemicals" such as icing sugar, must be used only as permitted by the APVMA approvals.
Bio-mechanical approaches
Drone brood removal
Many beekeepers in other countries use green drone comb to encourage the colony to raise a solid frame of drone brood. Varroa mites are preferentially attracted to drone brood because they can raise 2 full offspring cycles in drone cells.
The drone brood is allowed to be capped, and then removed and frozen to kill the mites and reduce the overall mite-load in the colony.
Failing to remove the drone comb before emergence will create massive mite loads in your colonies. This requires discipline and attention to detail.
Brood breaks
Varroa require capped cells in which to reproduce. Eliminating capped brood for a "brood break" eliminates their opportunity to reproduce, and renders them vulnerable to treatments like Oxalic Acid vaporisation and Thymol.
The queen is removed or isolated for 21 days, allowing all capped brood to emerge. A series of OAV or Thymol treatments are applied to kill 99% of the phoretic mites (exposed mites on bees).
"Shook swarm"
Another brood break approach is the "shook swarm". Bees from the brood box are shaken into a new brood box containing only foundation frames with no brood. All the remaining brood is frozen (or otherwise destroyed), killing reproducing varroa mites in capped cells. The colony must rebuild all the frames with new wax, and start a whole new brood cycle. This method does not address phoretic mites (those active on adult bees). It only removes reproducing mites in capped brood cells. To combat phoretic mites an additional treatment would be required (such as OAV or miticide strips) within 7-10 days ie before any capped brood is present.
High temperature treatment
This is an experimental treatment and has not yet been thoroughly proven
Varroa mites have a low tolerance to temperatures above about 39C, while honey bees can tolerate temperatures up to 42C for a period of time.
Hives are sealed up, and heated to 40-41C for several hours killing the mites.
This is extremely stressful to the colony and can result in brood die off and queen fertility issues. It can significantly harm the colony and cause absconding.
It is still questionable as to whether this is a viable or effective treatment approach.
VSH selective breeding
As mentioned earlier, selectively breeding varroa sensitive bees that are more resistant to the presence of varroa is a key strategy to managing varroa
"Host resistance" is the holy grail of dealing with a pest or disease as it means the host is able to resist or live with a pest or disease without the need for external interventions such as chemical treatments or manual manipulations.
The genetics of varroa resistance in european honey bees is not well understood at this stage, but there are several novel approaches to selective breeding that are being developed
UBeeO (Dr Kaira Wagoner) is a pheromone-based test that evaluates a colony's ability to detect "unhealthy brood odours" and remove brood that exhibits this odour. Varroa attacking larvae in the brood cause this odour, and colonies that detect, expose, and remove this brood are more successful at interrupting the mite life-cycle.
Harbo assay is a method of testing mite reproduction inhibition within a colony. This is an intensively manual testing approach that evaluates how effective a colony is at interrupting the life-cycle of the mite as it reproduces in drone cells.
Key resources that might help you get started.
APVMA treatment approval chart: https://honeybee.org.au/ahbic-varroa-treatment-table/
NSW DPI PrimeFacts Varroa Management https://www.dpi.nsw.gov.au/emergencies/biosecurity/current-situation/varroa-mite-emergency-response/managing-your-hives-with-varroa/primefact-varroa-mite-management-options-in-nsw
Bee Aware Australia - https://beeaware.org.au/
Honey bee health coalition
YouTube channel - https://www.youtube.com/@honeybeehealthcoalition1029
Varroa management guide - https://honeybeehealthcoalition.org/resources/varroa-management/
Randy Oliver - varroa sensei - https://scientificbeekeeping.com/
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