Bee Buzz Box August 2024 Mite Bee Part V – The Varroa Suggestion Box

Alan Wade

Canberra Region Beekeepers

Of course you remember the last time you visited Itching Down (Vernon and Burroway, 1972). I know because you will recall that the villagers had a wasp problem. Four million of them:

One hot summer in Itching Down,

Four million wasps flew into town.

They drove the picnickers away,

The chased the farmers from their hay,

They stung Lord Swell on his fat bald pate,

They dived and hummed and buzzed and ate.

But the problem, like Varroa, was not about to go away:

And the noisy, nasty nuisance grew,

Till the villagers cried 'What can we do',

So they called a meeting in the village hall,

And Mayor Muddlenut asked them all,'

What can we do?' And they said, 'Good question!'

But nobody had a good suggestion.

The town was abuzz, but they had a problem, one that had to be resolved. Australia now has its very own Varroa mites and soon they will be in every town, bee tree hollow and bee hive. At the starting gun and, from reports of experience overseas (Quigley, pers comm.), we might expect to be drowned in them.

Itching Down denizens found their own solution in the shape of a giant jam sandwich, for they were 'not a waspish sort of town'. Might we not find a similar solution to Varroa?

To get some clue as to how we might tackle this unwelcome intruder, let's turn to the remarkable findings made plain in Geographical distribution and selection of European honey bees resistant to Varroa destructor, sketched by Yves Le Conte and coworkers (2020). In their scoping review they chronicle pockets of honey bees that have gained the better of Varroa. Others have reported on this phenomenon, for example by Grindrod and Martin (2021) and by Loftus, Smith and Seeley (2016). Kohl and coworkers (2023) have demonstrated that surviving wild and unmanaged bees have much lower mite loads: colonies are further apart, they swarm more regularly and have increased Varroa tolerance. That tolerance can either be attributed to increased Varroa Sensitive Hygiene (VSH) or to decreased virulence of the Varroa–virus association. Breeders main focus is on improving VSH (Carreck, 2011). We can define these as bees as ones that survive well without any recourse to use of chemicals.

But far from these resistant bees being the solution to Varroa – a return to the good 'ole days of beekeeping – we discover that they tend to fall victim to the mite when translocated to Varroa disaster zones especially, but not only, as they outcross.

With this sobering state of affairs, let’s raid The Varroa Suggestion Box to discover what practical measures might be implemented to tame the dame. We identify five options for mite management:

• a leave alone strategy;

• a whack-a-mole (arachnicide treatment) strategy;

• a natural product knock down strategy;

• a natural defence strategy (employing natural host drone brood mite preference, swarming and absconding mechanisms); and

• a honey bee mite tolerant, better varroa resistant, strategy.

We might also reflect on the best way to assess the need for treatment, itself a vexed question. Ascertaining mite numbers and adjudging the critical point for intervention has been widely debated. The general consensus is that that point is realised when mite numbers reach a 2% infestation level. Various methods for making that assessment are outlined by the Colony Loss Honey Bee Research Association (COLOSS) (Dietemann et al., 2013) in their manual Standard methods for Apis mellifera pest and pathogen research.

A practical exemplar is a mixing a few of these options outlined by NSW DPI's Elizabeth Frost(2024) in an article published in The Australasian Beekeeper. From a swarm with a high Varroamite load captured from near the epicentre of the original Newcastle outbreak she treated the fledgling colony with Bayvarol strips. The colony built quickly and soon went into a honey flow where the only treatment employed was progressive removal of combs of just sealed drone comb – twelve in all – that would capture many newly emerged mites. The result: a good honey crop with mites kept well under control. Note that since oxalic acid is now in the process of being scheduled for use, you might soon employ this natural product in lieu of synthetic Bayvarol.

With over thirty years experience of mite control worldwide, we can point to many mite control successes and failures. A very broad sketch of these methodologies is outlined in a scoping paper prepared by AgriFutures Australia (Holmes et al., 2023).

1 Leave alone strategy

In the normal course of events doing nothing for your bees to control mites will result in their demise in a time frame of as little as two-to-three years. To give substance this, you will need only to witness the disappearance of bees emerging from tree hollows, ones you have watched for many past years. In any case swarms will become as rare as hen's teeth.

Yet there will be an exceptional colony that will survive though you are extremely unlikely to find one. In little more than a decade don't be surprised to find those same old bee trees humming back into business. Such instances tell us that there are innate (if uncommon) instances of population recovery.

Surprising as it may also seem, Africanised honey bees of central America (Apis mellifera scutellata hybrids) and seemingly all races of honey bees across the Africa continent maintain colonies with low mite numbers and correspondingly low virus loads. African bees are poorly studied so we know less than the whole story. Le Conte and coworkers (2020) cite the shorter brood development period of the Cape honey bee (Apis mellifera capensis), the absconding propensity of the East African honey bee (Apis mellifera scutellata) and the low infestation rate of brood amongst Ethiopian honey bees (Apis mellifera simensis) as factors conferring African bee Varroa tolerance. We might conclude that beekeepers in African and Central American countries, too poor to adopt western control measures, have been blessed with mite resistant bees (see Unboxed).

Some Canberra Region Beekeepers club members may recall the then CSIRO mite guru Denis Anderson telling us that Papua New Guinea highlanders got a very nasty shock when a sister mite, Varroa jacobsoni (Figure 1), arrived to kill off their 'domesticated' bees. Like Tom Seeley's Arnot Forest bees, even with viruses, they have bounced back (Ray et al., 2023).

Figure 1 Varroa jacobsoni

Source: The Beekeeping Family, 2011).

I know of one beekeeper in southern Greece whose only Varroa control measure has been to resort to the occasional dusting of brood frames with icing sugar. I like to conjecture that this beekeeper, famed for keeping bees as naturally as possible, may be running the local bee Apis mellifera cecropia and that bee may have acquired some natural immunity to the mite. Sceptical of the efficacy of such cursory treatment I was surprised to discover that it actually works quite well. The clear proviso is that hives get this 'feather dusting treatment' every few weeks (Oliver, 2007). Randy Oliver tried it, finally got it work, and then abandoned it: it was too much work and was really only a stop gap measure.

But no sensible beekeepers will ever hang out for the thirty or more years for mite tolerance to just kick in. Let's look deeper into The Varroa suggestion box.

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Unboxed

The do nothing camp have a surprising ally. Beekeepers in most of Africa, South and Central America and eastern Russia have been gifted with wild bees that have learnt to live with Varroa. Unable to afford treatment, they have sailed into the sunset with mite accommodating bees. More realistically we might conclude that The Western honey bee, despite its mite prone status is, after all, just another Apis species being one ever only having been challenged by the tracheal mite.

Tellingly we now know that the Isle of Wight Disease has been attributed to Cloudy Wing Virus, exacerbated by sustained poor weather conditions and overstocking. With the wisdom of hindsight it now appears that Western honey bees had all long learnt to live with Acarapis mites, all three known species.

Paradoxically better resourced western beekeepers, relying entirely on knockout treatment, have hit a brick wall. Mites have learnt, or are learning, to live with arachnicides. At the same time the Varroa-virus complex has seemingly become less treatable and more virulent. Beekeepers may have won the battle but, in the long term, will likely lose the war.

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In an amusing aside to the Isle of Wight (IoW) saga, we discover that the very alert Leslie Bailey(1964) from UK Rothamsted Research came up with this salutary message:

Overenthusiastic beekeepers were, and still are, a major hazard for bees. Whatever the causes of their bees' misfortunes, however, beekeepers used Acarapis woodi after it was discovered as the scapegoat, and so it inherited the aura of the myth of the IoW disease. The significance of the myth is that lack of sufficient knowledge allowed it to develop and dominate thought, and so to cause much misdirected apprehension and wasted effort.

From this we learn that the original findings of Rennie and coworkers (Rennie et al., 1921a, 1921b; Harvey, 1921) and Vernon (1921) were misguided in the interpretation of their research findings and that Acarapis had been a long and assuredly widespread parasite of Apis mellifera but not one occasioning large scale demise of honey bees.

2 Whack-a-mole arachnicide treatment strategy

Also known as the shotgun approach, whack-a-mole – hitting mites hard with synthetic arachnicides – proved to be an effective means of controlling Varroa mite. So we in Australia will go down the same track and almost certainly see large scale use of miticide strips. Touted as the solution to the Varroa mite arachnicides have worked a treat. Simple and widely recommended for use, they will be widely employed by commercial and migratory beekeepers too time pressed to adopt mite suppression techniques modelled on the behaviour of their Apis cerana hosts.

However anyone who has used a sledgehammer and allowed a thumb or big toe to get in the way realises that there is always some risk of collateral damage. Some arachnicides are persistent and small amounts end up in beeswax altar candles and, if misused, in table honey. We might add that such persistence in the comb provides the opportunity for mites to build their tolerance to treatment. Coumaphos and fluvalinate are notable examples of failed efficacy. They are no longer effective in treating bees in north America and, not surprisingly, American beekeepers are abandoning their use.

Then there proved to be an indirect effect of use of miticides on bees themselves. While largely selected for low toxicity to bees, there are always, as with most drugs, some side effects. For example queens are often quickly superseded. Commercial beekeepers are now often combining treatment with requeening that is after treating with a product such as Api-Bioxal (oxalic acid).

But miticides have generated another problem of a more insidious nature. Hard chemicals mask bee defences preventing their evolving to become mite tolerant – they do not allow bees to evolve to look after themselves. A particular problem has arisen in the association of Varroa with viruses notably Deformed Wing Virus (see Boxed In).

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Boxed In

Wilfert and coworkers (2016) track the origins and spread of Deformed Wing Virus (DWV) as one of several viruses promoted by mites. The virus is neither of Varroa destructor nor Apis cerana origin as is sometimes supposed. Rather DWV has spread to this Asian bee from its original host Apis mellifera. The virus itself has evolved, become more virulent and, with mites vectoring larger amounts of virus than the bees themselves originally did, it has become a resurgent pathogen! Certainly DWV not only causes colony mortality in managed Apis mellifera populations but it also impacts wild populations.

The Apis cerana Asian bee clade (A. cerana, A. koschevnikovi, A. nigrocinta…) are the original hosts of the Varroa family just as the Apis dorsata clade are the native hosts of Tropilaelaps mites. Both Varroa and Tropilaelaps vector and amplify DWV.

Also of great import is the fact that DWV is impacting and spreading to bees in general, for example a cause of decline in many native bee species and in bumble bee populations and on biodiversity.

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As Randy Oliver and many others are now saying, the use of arachnicides to control Varroa has failed and we need to find better solutions to enable bees to look after themselves, a topic we will return to.

3 Natural product knock down strategy

There are a range of natural products that are lethal to mites (Figure 2). There action is of short duration and, unlike synthetic miticides that may be left in the colony for a month or (unwisely) more, they are simply knock down agents. But how effective are these natural products and what needs to be done to ensure the mites, and not sensitive brood, are exposed to these agents? While their action is quick and sharp measures such as admixing oxalic acid with glycerine or impregnating strips can extend their treatment efficacy.

Of these natural products, oxalic acid (found in rhubarb), formic acid (think bull ants), thymol (a terpene found in sage) and hop β acids (Kostrzewa et al.,2016) (α and β hop acids are the bitter principles of beer) are the only well tested products. Others such as menthol (from the mint family) and a host of other chemicals have been employed, but none of these have been scheduled for use.

Figure 2 A menagerie of natural products for treating mites:

(a) β hop acids;

(b) thymol;

(c) menthol;

(d) oxalic acid; and

(e) formic acid.

There is general consensus that mites cannot build resistance to these naturally occurring plant metabolites. For beekeepers, ever keen to find a home made solution to any malady, the small amounts of these chemicals found in rhubarb leaves, sage bushes, half a cup of ants or in a sky reaching beer hop vine will not produce enough material to constitute an effective dose. Popping a few rhubarb leaves or crushed ants under a hive lid simply wont work. As a rule stick to formulations approved for use and glove and mask up as recommended.

It is important to read widely and adopt official Department of Primary Industry and Australian Honey Bee Industry Council guidelines. Despite you best efforts you will still encounter colony losses, so try to requeen bees heavily infested with mites – with the best available stock – or euthanase weak colonies especially those badly co-infected with the likes of chalk brood and Nosema. And if you are as averse as I am to using synthetic miticides then judicious use of natural products and adopting techniques such as removal drone comb as it is sealed is a strategy for reducing Varroa that can be extended to a honey flow. The drone producing season depends of course on where you live, so a mix of intervention strategies will be imperative.

4 Natural defence strategy

It was only some time after western honey bees encountered long mite-tolerant eastern honey bees that the Korean and the Japanese-Thai halotypes – a few of a number – of Varroa destructor parasitising Apis cerana jumped ship to our honey bees: when the mites came up the tights came down. So started the saga of the Varroa epidemic (Carreck and Neumann, 2010; Berthoud et al., 2010).

In retrospect it is sobering to recognise that the natural hosts of parasitic bee mites – there are about a dozen such blood (haemolymph) suckers – are intrinsically mite tolerant and have been so for many many millennia. In the long term only those mites that allowed their Apis species hosts to survive have themselves survived.

We now of course know that parasites of honey bees in general also harbour viruses but, with their native hosts restricting the number of mites present, the virus loads and the mites were never lethal. The subtleties and range of factors occasioning colony collapse due to viruses are outlined by Carreck, Ball and Martin (2010).

Against this background of freeloading mites what might we learn from bees themselves? In a short time (less than 100 years) a number of western honey bee populations have come up with the defences that all their Asian cousins acquired over millions of years. Le Conte and coworkers (2007, 2020) identify some of the many pockets of global Varroa tolerance amongst western honey bees and identify as best possible the mechanisms by which they have achieved that level of resilience. Locke (2016) similarly identifies specific regional mite-resistant biotypes systematically describing each population. Others have described Varroa-tolerant populations, Rozenkranz (1999) in South America, Oddie, Dahle and Neumann in Norway (2017), Rinderer and coworkers in eastern Russia (Rinderer and Coy, 2020; Rinderer et al., 2001), Fries and coworkers (2006) in a Nordic climate and Riley (2024) in Ireland. By and large, however, Varroa tolerance has not translated to such bees being introduced elsewhere well not in the sense that once established that tolerance is lost when queens are superseded or colonies swarm. As Le Conte and coworkers (2020) have surmised:

Since the emergence of Varroa as a serious pest of Apis mellifera, considerable time, effort and finance has been devoted to understanding the mechanisms underlying varroa resistance and to breeding bees resistant to the mite. However, progress has often been slow, and some desirable traits, demonstrable in experimental colonies, show low heritability or, alternatively, show benefits that are too small to render them practicable in breeding programs. Another problem is that bee populations apparently resistant to varroa in one location sometimes cease to remain resistant when moved elsewhere and exposed to different environmental conditions or exposed to different mite populations.

Brian Johnson (2023) makes a case for a rather more nuanced understanding of the inherent Varroa resistance of Africanised honey bees in the central Americas. Based on genetics and behavioural observations, he attributes much of the resilience to particularly vigorous grooming behaviour, to very effective mite dismemberment, to very effective patrol and removal of mite infested brood and to generally shortened brood raising time (~18.5 days) for African races versus 20-21 days for European races of the species. He also tracks the changing behaviour of bees in central American apiaries stocked with European bees surrounded by wild colonies – Africanised drones mating with European queens – with a resultant shift in genetics. In any case Africanised honey bees appear to produce low fertility mites, hypothesised to be caused by higher activity of bee larvae resulting in high mortality of the sole male mite that is laid first.

Johnson (2023) observes that bees in Brazil suffer essentially no varroa damage while there is notable if slight varroa damage to bees in Mexico. Brazilian bees host the less pathogenic Varroa jacobsoni mite and this was originally hypothesised to explain the between country difference in varroa susceptibility. However Varroa destructor is now in Brazil and the impact has not changed so that theory has been discounted.

If we add in the increased swarming proclivity and smaller nests of African bees we might begin to conclude that African and European races of honey bees are distinctively different Apis mellifera ecotypes subject to very different environmental influences. Johnson's (2023) overall thesis is that European and African honey bees are best adapted to cooler and tropical climes respectively, but only those of African origin are naturally Varroa tolerant.

This backgrounding leads us back to the topic of intervention, measures that might be adopted to reduce mite loads. Particularly effective are the techniques for separating bees from their mite laden brood outlined by Uzunov, Gabel and Büchler (2024) in their book Summer brood intervention and by others such as Büchler et al. (2020) and Kirsty Stainton (2022). Their ploys can entirely circumvent use of any chemicals or only require their judicious use. All these procedures (apart from treating swarmed bees upon capture) require radical interruption to the brood cycle so are difficult to enact on a commercial scale. Severally the techniques either confine the queen to allow brood to mature and emerge to force mites to become phoretic – where mites are exposed and can be more effectively treated – or physically separate bees from their brood – as in shook swarming.

The downside to techniques that mimic natural defence are those of an intensive labour requirement and the loss of brood raising attendant to queen caging. Techniques that keep the colony queen laying can, however, be used to advantage. In these queens are encouraged to lay out drone comb, mites being preferentially attracted drone brood and that comb being cycled out promptly as it is sealed, that is well before drones emerge. Such techniques would appear to be sustainable but require close attention by the beekeeper making them best suited to the sideline beekeeper.

5 Honey bee mite resistant strategy

Enter a new breed of queen breeders who are making slow but steady progress raising Varroa resistant stock. Those successfully doing so have discovered bees capable of detecting and removing brood affected by other diseases (Riley, 2024). But these are but one of a number of defensive traits selected for, some confined to particular pockets of mite tolerant honey bees (van Alphen and Fernhout, 2020). Specific traits, often routinely observable, have been targeted: auto and allogrooming, brood uncapping, mite dismemberment, healthy brood recapping... Several or all must pass a certain threshold for mite removal to be effective.

Harking back to the 'do nothing scenario' we discover that our honey bees have a latent genes, often poorly expressed, that enable the fittest to survive. Once selected for and retained we might just get sustainably mite tolerant and productive bees. For those sceptical of this eventuality, breeders are now producing stock with a modicum of chalkbrood and other brood disease hygienic behaviour.

Implicit to this optimism are the many efforts to raise Varroa tolerant bees: the USDA's program to employ Primorsky (eastern Russian) mite tolerant Apis mellifera stock (Rinderer and Coy, 2020), the Arista program in Hawaii (Arista Bee Research, 2018), early tolerance in South America (Rosenkranz, P., 1999), the New World Carniolan project (Apis Information Resource Centre, 2024), the UK Westerham project (Riley, 2024) and the Randy Oliver scheme (Oliver, 2023, 2025a, 2025b, 2025c, 2025d, 2026) to raise his mite resistant Golden West queens. Few such queens are available commercially and those that are will attract a premium price. By way of example queens from the Oliver stable are only now just being offered for sale through commercial breeders such as Nature's Nectar (2024). They report that:

The Olivers don’t select for looks and use their queens’ variation in color patterns as an indicator that they are maintaining enough genetic diversity in their stock. But they do select for performance.

They breed only from queens whose colonies are very gentle and healthy, exhibited above average honey production, and proved strong for almond pollination.

Westerham Beekeepers (seemingly many others) have been similarly successful in operating apiaries with carefully selected stock, albeit mainly for their own use. Their scheme, to operate their bees entirely treatment free, has been seventeen years in the making (Riley, 2024).

Are Australian beekeepers and queen breeders able to do their bit? This is hard to say. However buying the cheapest rather than the best – if shopping at the supermarket is any indication – is the norm. The Australian Queen Bee Breeders Association (AQBBA), if not the broader beekeeping industry and queen producers, are gearing up to produce Varroa resistant stock to counter the spread of the mite. Established way back in the 1980s, AQBBA's mission has been to breed productive, disease resistant and tractable stock. From a pool of 500 high performance stock from New South Wales and Queensland apiaries, queens from ten colonies demonstrating a useful level of Varroa resistance (Unhealthy Bee Odour [UBeeO] tested) have now been distributed to AQBBA breeders along the eastern seaboard. These untested but ideally mated queens now being used to raise stock that are being assessed for Varroa Sensitive Hygiene performance. The coordinated program is in its earliest stages of development, some queens raised being tested in the Varroa infested Newcastle area.

The exigencies of breeding and the likely future establishment of regionally stable Varroa resistant populations is some while off. For now, the alternative to intensive mite management will be to purchase not-so-cheap queens whose progeny, also selected for productivity and gentleness, that have a modicum of Varroa resistance.

This all said, the question remains as to whether science and beekeeping practice will ever match the Varroa resistance already achieved by African bees and pockets of surviving wild bees. Have these bees been smarter in finding their own solution? 

My bet is on the AQBBA achieving this lofty goal, not on spending most of my time keeping mites in check.

Readings

Andrea Quigley, Editor of The Beekeepers Quarterly (pers. comm.).

Apis Information Resource Centre (accessed 31 May 2024). Sue Cobey and the New World Carniolan Breeding Program. https://beekeep.info/a-treatise-on-modern-honey-bee-management/genetic-management/sue-cobey-and-the-new-world-carniolan-breeding-program/

Arista Bee Research (May 2018). Documentary of Brandpunt Varroa resistant breeding project on Hawaii. https://aristabeeresearch.org/

Bailey, L. (1964). The Isle of Wight disease: The origin and significance of the myth. Bee World 45(1):32–37. https://doi:10.1080/0005772X.1964.11097032

Berthoud, H., Imdorf, A., Haueter, M., Radloff, S. and Neumann, P. (2010). Virus infections and winter losses of honey bee colonies (Apis mellifera). Journal of Apicultural Research 49(1):60-65. https://doi:10.3896/IBRA.1.49.1.08

Büchler, R., Uzunov, A., Kovačić, M., Prešern, J., Pietropaoli, M., Hatjina, F., Pavlov, B., Charistos, L., Formato, G., Galarza, E., Gerula, D., Gregorc, A., Malagnini, V., Meixner, M.D., Nediċ, N., Puškadija, Z., Rivera-Gomis, J., Rogelj Jenko, M., Smodiš Škerl, M.I., Vallon, J., Vojt, D., Wilde, J. and Nanetti, A. (2020). Summer brood interruption as integrated management strategy for effective Varroa control in Europe. Journal of Apicultural Research 59(5):764-773. https://doi.org/10.1080/00218839.2020.1793278

Carreck, N. and Neumann, P. (2010). Honey bee colony losses. Journal of Apicultural Research 49(1):1-6. https://doi:10.3896/IBRA.1.49.1.01

Carreck, N.L. (2011). Chapter 7 Breeding honey bees for Varroa tolerance in Carreck, N.L. (ed). Varroa - Still a problem in the 21st Century? International Bee Research Association. https://www.researchgate.net/publication/262933100_Breeding_honey_bees_for_varroa_tolerance

Carreck, N.L., Ball, B.V. and Martin, S.J. (2010). Honey bee colony collapse and changes in viral prevalence associated with Varroa destructor. Journal of Apicultural Research 49(1):93-94. https://doi:10.3896/IBRA.1.49.1.13

Dietemann, V., Ellis, J.D. and Neumann, P. (2013). The COLOSS Beebook Volume II, Standard methods for Apis mellifera pest and pathogen research: Introduction. Journal of Apicultural Research 52(4):1-4. https://doi:10.3896/ibra.1.52.4.16

Fries, I., Imdorf, A. and Rosenkranz, P. (2006). Survival of mite infested Varroa destructor honey bee Apis melliferacolonies in a Nordic climate. Apidologie 37(5):564-570. https://doi:10.1051/apido:2006031 https://www.apidologie.org/articles/apido/pdf/2006/05/m6039.pdf

Frost, E. (2024). Case study: Varroa managment in a high infestation zone. The Australasian Beekeeper 125(11):44-46.

Grindrod, I. and Martin, S.J. (2021). Parallel evolution of Varroa resistance in honey bees: a common mechanism across continents? Proceedings of the Royal Society B 288(1956):20211375 https://royalsocietypublishing.org/doi/full/10.1098/rspb.2021.1375

Harvey, E.J. (1921). (3) Isle of Wight disease in hive bees—Experiments on infection with Tarsonemus woodi, n. sp. Earth and Environmental Science Transactions of The Royal Society of Edinburgh 52(4):765-767. https://doi.org/10.1017/S0080456800015994

Holmes, M.J., Gerdts, J.R., Grassl, J., Mikeheyev, A.S., Roberts, J.M.K., Remnant, E.J. and Chapman, N.C. (September 2023). Resilient beekeeping in the face of Varroa. AgriFutures Australia. https://agrifutures.com.au/product/resilient-beekeeping-in-the-face-of-varroa/

Johnson, B.R. (2023). Honey bee biology. Chapter 16, pp. 290-300. Princeton University Press.

Kohl, P.L., D'Alvise, P., Rutschmann, B., Roth, S., Remter, F., Steffan-Dewenter, I. and Hasselmann, M. (2023). Reduced parasite burden in feral honeybee colonies. Ecological Solutions and Evidence 4(3):e12264. https://doi.org/10.1002/2688-8319.12264 https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1002/2688-8319.12264 https://www.biorxiv.org/content/biorxiv/early/2022/07/19/2022.07.18.500457.full.pdf https://www.researchgate.net/publication/373049674_Reduced_parasite_burden_in_feral_honeybee_colonies

Kostrzewa, D., Dobrzyńska-Inger, A., Rój, E., Grzęda, K. and Kozłowski, K. (2016). Isomerization of hop extract α-acids. Journal of the Institute of Brewing 122(3):493-499. https://doi:10.1002/jib.349

Le Conte, Y., de Vaublanc, G., Crauser, D., Jeanne, F., Rousselle, J.-C. and Bécard, J.-M. (2007). Honey bee colonies that have survived Varroa destructor. Apidologie 38(6):566-572. https://doi:10.1051/apido:2007040 https://link.springer.com/article/10.1051/apido:2007040#citeas

Le Conte, Y., Meixner, M.D., Brandt, A., Carreck, N.L., Costa, C., Mondet, F. and Büchler, R. (2020). Geographical distribution and selection of European honey bees resistant to Varroa Insects 11(12):873–. https://doi:10.3390/insects11120873 https://www.semanticscholar.org/reader/7021c98640747071e4c9d588a052319ca546f3ef

Locke, B. (2016). Natural Varroa mite-surviving Apis mellifera honeybee populations. Apidologie 47(3):467-482. https://doi.org/10.1007/s13592-015-0412-8 https://link.springer.com/article/10.1007/s13592-015-0412-8

Loftus, J.C., Smith, M.L. and Seeley, T.D. (2016). How honey bee colonies survive in the wild: testing the importance of small nests and frequent swarming. PLOS One 11(3):e0150362 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150362

Nature's Nectar (15 January 2024). Introducing the Randy Oliver golden western queens! https://www.naturesnectarllc.com/introducing-the-randy-oliver-golden-west-queens/

Oddie, M.A., Dahle, B. and Neumann, P. (2017). Norwegian honey bees surviving Varroa destructor mite infestations by means of natural selection. PeerJ 5:p.e3956. https://peerj.com/articles/3956/

Oliver, R. (2007). IPM 5 Fighting Varroa: Biotechnical tactics Part 2: The one-two punch. Scientific Beekeeping. https://scientificbeekeeping.com/fighting-varroa-biotechnical-tactics-ii/#:~:text=The%20concept%20is%20simple%3A%20insert,frame%20before%20the%20mites%20emerge

Oliver, R. (2023). Selective breeding progress report 2023. Scientific Beekeeping. https://scientificbeekeeping.com/selective-breeding-progress-report-2023/

Oliver, R. (2025a). Selective breeding for mite resistance Part 1. Scientific Beekeeping. https://scientificbeekeeping.com/selective-breeding-for-mite-resistance-part-1/

Oliver, R. (2025b). Selective breeding for mite resistance Part 2: Concepts. Scientific Beekeeping. https://scientificbeekeeping.com/selective-breeding-for-mite-resistance-part-2-concepts/

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