On June 22, 2022, during a routine biosecurity inspection in New South Wales, Australia, the Varroa mite was detected in sentinel hives at the port of Newcastle. As a result, the government implemented rigorous eradication measures, including quarantine, feral colony poisoning, and the burning of several thousand hives. The NSW Department of Primary Industries (DPI) is leading the well-funded eradication and surveillance program 1,2. They also had successfully eradicating the mite in 2016, 2019, and 20205.
Since May 2023, new varroa-infected colonies have been detected. Some were further into the mainland, most likely due to prohibited hive movement. In September 2023, the DPI has partially revised their policy, leading to the relaxation of some of the strict measures, followed by an abandonment of eradication in September the 20th. In this text, I will develop the reasons why I think the varroa mite will eventually spread all over Australia and why I believe pest management is the most pragmatic option.
Reason # 1: It spreads in too many ways.
Varroa mite spreads rapidly where there are honey bees. In particular, there are many ways that a mite could migrate from one colony to another:
- Forager drifting. This is phenomenon that transfers low mite numbers, not only between the nearby hives, but from one apiary to the nearby apiary.
- Robbing. Ordinary robbing by foragers exchanges pathogens, and of course, mites. Open feeding practices also have same effect.
- Absconding. Heavily infected Colonies abscond and they carry the mites with them. These colonies usually do not survive, but in this way the odds of transmission to healthy colonies increase.
- Among Drones. Drones carry significant mite load and they exchange colonies frequently. The mite may also hitchhike a queen during mating.
- Robbing of collapsing hives. This is the most infectious transmission scenario⁶. The mite follows a parasitoid pattern on a population level, meaning that its population is “programmed” to destroy the colony.
- With migratory beekeeping. Whereas collapsing hives affect the intensity of the outbreak, migratory beekeeping affects the extensity of the outbreak.
Empirically, the higher the density of hives and apiaries in an area the fastest the spread and the higher the infestation levels. The mite is quite elusive and makes surveillance for eradication an operational nightmare.
Reason #2. Unsuitable Sampling Methods
The standard procedure by DPI for sampling varroa are mandatory alcohol washes. But alcohol wash in practice is an non reliable method when it comes to detecting low mite infestation levels. Early stages of varroa infection cannot be spotted easily. The infection gets evident only when has already spread to other colonies. Sometimes the mites do not detach from the bees during the alcohol wash. That is because most of the mites are well protected in the abdomen segments of the honey bee from where they feed themselves. A more reliable test to see if mite is present is by applying a synthetic acaricide and sticky boards.
Reason #3. It has been found too far from the initial site
The 2023 cases suggest that the mites may already have spread deep into the mainland, and also indicates how fast it can spread outcompeting the response of the authorities.
Reason #4. Lack of hands-on experience.
Despite the surveillance programs are well organized, they are run by staff with no hands-on experience with the varroa mite. Admittedly they are experts in eradication, but that is it. Varroa management is notorious for the lack of standardized methods and treatments. That is because of the complex nature of the parasite. Practically, Varroa management requires lots of improvisations and hive manipulations. “Follow the label” literally, or go 100% by the book and your life will be full of surprises. In Australia where colonies have little or no brood breaks hive manipulations would be crucial for the efficacy of treatments.
Draconian Measures3
The authorities applied a relatively simple eradication concept: a 10km eradication zone, followed by a 25km surveillance zone. There was zero tolerance if mites were found within the eradication or surveillance zones. To some, this may seem like a more dystopian version of the COVID pandemic restrictions. The point is that beekeepers within the infected zones were seeing their fortunes perish and sacrificed for the “greater good”. Reimbursement did not fix things, as no bees were allowed in the same place the following year. As more beekeepers fear the potential consequences of getting the mite, the chances of hiding an infection from the authorities increase. Human psychology does not always work with “greater good” schemas. So, it could have taken one elusive beekeeper to start an outbreak again.
But, varroa is manageable
Now the good news. Varroa has been for decades around the globe. In regions like Africa or central Latin America the honey bees have even beaten the mites. Robust races like Apis Mellifera Mellifera also display resilience. However, this is not the case for the honey bees of the C and O lineage and the temperate zones. But after all, Australian beekeepers should not be afraid of the mite because varroa is manageable. There must have been enough of “varroa-terror” from the news and the government. Besides, there is a global trend to keep citizens under a constant state of anxiety (supposedly as a means of “crowd control”). Despite the moderate successes in varroa management that require a lot of improvisations, my advise would have been: Keep calm and carry on, as the WWII slogan sated.
The “cost-benefit” fallacy
Before we get into pest management, let’s examine the economic aspect of the infection. Australia’s beekeeping industry enjoys high profits from being varroa-free: High honey and wax prices, competitive pollination services and varroa free nuclei exports. So, the estimated losses from a future varroa epidemic will enormously outweigh the cost of any eradication measures. The problem is that this binary logic will always decide in favor of eradication policies. Zoonotic pests do not follow abstract “game theories”, and, besides the hidden costs of eradication measures, this is not how animal husbandry work. We are in the 21st century and it’s time to use science and effective bureaucracy to move forward.
Reasonable Epizootic measures
Here are few things from our experience on how to minimize risks and exposure to the parasite. The primary goal should have been to make this spread varroa as slow as possible. Containing the epizooty will give plenty of time for the beekeepers and the honeybees to adapt, as well as will absorb the industry damages.
- Varroa is contained where collapsing hives within an apiary are brought to minimum. Collapsing hives disperse numerous mites to the nearby hives. Note that there is no correlation between varroa infestation levels and the point of collapse, a fact that puzzled European scientists⁴ investigating varroa in the late 1990’s.
- Pollination movements under surveillance. This is the way the mites “travel” long distances. Surveillance means that a stock cannot move into an uninfected area without control and vise versa for beekeepers entering the infected zones.
- Application of treatments to keep varroa levels constantly low. The the lack of brood breaks in Australian colonies will make this challenging, but not impossible. Low mite levels also keep the viral levels low and diverse. On the contrary, high mite levels apply all sorts of bad evolutionary pressures onto the viruses, producing more virulent strains. The virus problem will be unnoticeable at the beginning, but as the epizooty progresses viruses will become an issue. Despite no Deformed Wing Virus was reported so far in Australia, it is most likely that there will appear soon. Finally, chasing and poisoning feral infected hives is impractical. So, the resources must be spend wisely.
Natural “Mite Bombs”
Treatment free practices in newly infected areas would be a problem. Treatment-free enthusiasts use various practices based on 2-3 theories. Firstly, they use varroa infestation as a “screening tool” to spot the supposedly resistant hives among the infected. Secondly, they believe that the exposure to high parasite levels trains the bees’ social and individual immune system. Thirdly, they believe that bringing the bees closer to their natural state will help them cope with the parasite. These premises are highly questionable, but even if they were 100% successful means that every apiary nearby will be infected with high mite loads. Gradual and controlled refrain from treatments is a more pragmatic strategy, but it should be allowed in areas that have varroa established for several years.
Secondary Mite Outbreaks
After varroa developed a relative resistance to synthetic acaricides a phenomenon called secondary outbreak emerged. In such cases, high mite loads appear in treated hives with a phenomenal virulence. It is an epidemic within the epidemic. Unfortunately, such mite resurgences are a commonplace in countries with high hive density like it happened in Greece in the late 2010’s. I cannot describe the phenomenon here, but it can be controlled by alternating the synthetic/organic acaricide mode of action. This presupposes that beekeepers have easy access to at least two conventional acaricides and one organic. So, secondary outbreaks must be taken seriously, given the fact that the mites already carry significant resistance to acaricides. As we are not in the 1980’s and several treatments are available, it is highly likely that the epizooty will be under control the first 2-3 years. No significant hive losses are likely to be observed. In this scenario, a potential localized mite or viral resurgence could do more harm than the initial wave.
Experience from New Zeeland infestation indicates that varroa will take decades to spread. In particular, New Zeeland had the mite since ’98 while the measures ended in 2009. It took two decades for the mite to invade the whole country. The vast Australian continent will be challenging even from the varroa’s perspective. There is a chance that remote areas would remain varroa free. With the knowledge we have accumulated since the late 70’s, maybe there are more possibilities than ever to get the upper hand and make peace with the mite.
George Mitsikas (chemist, amateur beekeeper),
(Revised version 20/09/2023)
NOTES
- See daily reports of emergency situation here: https://www.dpi.nsw.gov.au/emergencies/biosecurity/current-situation/varroa-mite-emergency-response
- https://www.outbreak.gov.au/current-outbreaks/varroa-mite
- Drakon or Draco, was the first recorded legislator of Athens in Ancient Greece. He replaced the system of oral law by the written Draconian constitution. The laws were notoriously harsh and most of them had the death penalty. As one may guess Draco had an unfortunate end.
- See the Rothamsted experiments that I describe in Viral infections and Varroa- Part I.
- Although not all these cases were related to the virulent varroa species, but to a varroa species of the asian bees.
- Recent Randy Oliver’s experiments suggested that a collapsing colony has a high drift tendency and drift is more infectious than robbing.
The Beekeeping Lab 
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