The Giant Jam Sandwich
Alan Wade
With keepers of bees transfixed by the
Varroa problem where are we fifty years on?
Of course you remember the last time you visited Itching Down.i 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 overseasii, 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, Marina Meixner, Annely Brandt, Norman Carreck, Cecilia Costa, Fanny Mondet and Ralph Büchler.iii 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 Martiniv and by Loftus, Smith and Seeley.v Kohl and coworkersvi 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 complex. Breeders main focus is on improving VSH.vii We can define these bees as ones that survive well without or with minimal 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 look inside 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 (miticide 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 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 3% infestation level. Various methods for making that assessment are outlined by the Colony Loss Honey Bee Research Association (COLOSS)viii in their manual Standard methods for Apis mellifera pest and pathogen research.
A practical exemplar is mixing a few of these options as outlined by NSW DPI’s Elizabeth Frost in an article published in The Australasian Beekeeperix. From a swarm with a high Varroa mite load captured from near the epicentre of the original Newcastle outbreak she treated the fledgling colony with easy to employ 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 (=Flumethrin, a pyrethroid).
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 Australiax.
Scheme 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 hens’ 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 African 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 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 on African bees 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 (Unboxed).
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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. After all we might conclude that the European bee is just another honey bee. The European honey bee has ever only been challenged by the tracheal mite and to that mite it has seemingly adapted well.
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 and not to the tracheal mite. With the wisdom of hindsight it now appears that Western honey bees had all 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 miticides. 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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More surprising, however, has been the Cuban experience. Importation of bees has long been prohibited and treatment of Varroa was likewise outlawed.xi So when Varroa arrived it won and of course beekeepers lost out. However Cuba now runs nearly one quarter of a million colonies entirely chemical treatment free and has now done so for over twenty years. In the transition days they did practice drone trapping and oxalic acid treatment.
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.xii
Figure 1 Varroa jacobsoni.xiii
Notes: Being an arachnid, Varroa has 8 legs, not just the 4 depicted. Both Varroa jacobsoni and Varroa destructor are indistinguishable unless profiled genetically.
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.xiv 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 delve deeper into The Varroa suggestion box.
In an amusing aside to the Isle of Wight (IoW) sagaxv, we discover that the very alert Leslie Bailey from the UK Rothamsted Research came up with this salutary messagexvi:
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 were misguided and that Acarapis had been a long and assuredly widespread parasite of Apis mellifera but not one occasioning large scale demise of honey bees.
Scheme 2 Whack-a-mole miticide treatment strategy
Also known as the shotgun approach, whack-a-mole – hitting mites hard with synthetic miticides – proved to be an effective means of controlling the 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, miticides 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 native 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 miticides 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, those 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 they requeen after treating with products such as Api-BioxalTM and Aluen CAP® (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 find ways to look after themselves. A particular problem has arisen in the association of Varroa with viruses notably Deformed Wing Virus (see Boxed In)xvii.
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Boxed In
Wilfert and coworkers 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 the 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 sayingxviii, the use of miticides to control Varroa has failed and we need to find better solutions to enable bees to look after themselves. This experience is echoed in Europe. In a note from one of the editors of the British magazine The Beekeepers Quarterly I received this cautionary note:
The hard miticides worked brilliantly at first, then ended up creating resistant mites. We never left our strips in for too long, and followed the instructions. Yet our mites became treatment-resistant soon enough. Plenty of beekeepers left the strips in almost [in]definitely because they thought that was best. Obviously it isn’t, you just get resistant mites more quickly.
There are, however, other approaches emerging both in North America and in Europe and we shall explore those in Part B.
Readings
iVernon, J.V. and Burroway, J. (1972). The giant jam sandwhich. Houghton Mifflin Harcourt.
iiQuigley, A. Editor of The Beekeepers Quarterly (pers. comm.).
iiiLe 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 destructor. Insects 11(12):873–. doi:10.3390/insects11120873 https://www.semanticscholar.org/reader/7021c98640747071e4c9d588a052319ca546f3ef
ivGrindrod, 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
vLoftus, 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
viKohl, 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. doi.org/10.1002/2688-8319.12264
viiCarreck, 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
viiiDietemann, 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. doi:10.3896/ibra.1.52.4.16
ixFrost. E. (2024). Case study: Varroa managment in a high infestation zone. The Australasian Beekeeper 125(11):44-46.
xHolmes, 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/
xiLuis, A.R., Grindrod, I., Webb, G., Pérez, A. and Martin, S.J. (2022). Recapping and mite removal behaviour in Cuba: home to the world’s largest population of Varroa-resistant European honeybees. Scientific Reports 12:15597. https://doi.org/10.1038/s41598-022-19871-5
xiiRay, A.M., Gordon, E.C., Seeley, T.D., Rasgon, J.L. and Grozinger, C.M. (2023). Signatures of adaptive decreased virulence of deformed wing virus in an isolated population of wild honeybees (Apis mellifera). Proceedings of the Royal Society B 290(2009):20231965. https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2023.1965
xiiiThe Beekeeping Family (21 May 2011). Biologia Y Anatomia de la Varroa jacobsoni – Biology and anatomy of mites. https://lafamiliapicola.blogspot.com/2011/05/anatomia-y-biologia-de-la-varroa.html
xivOliver, R. (May 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
xvRennie, J., White, P.B. and Harvey, E.J. (1921). Isle of Wight disease in hive bees. Transactions of the Royal Society of Edinburgh 52:737-779. https://ia601305.us.archive.org/5/items/cu31924003692633/cu31924003692633.pdf
Rennie, J., White, P.B. and Harvey, E.J. (1921). (1) Isle of Wight disease in hive bees—The etiology of the disease. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 52(4):737-754. doi.org/10.1017/S0080456800015970
White, P.B. (1921). (2) Isle of Wight disease in hive bees—The pathology of Isle of Wight disease in hive bees. Earth and Environmental Science Transactions of The Royal Society of Edinburgh 52(4):755-764. doi.org/10.1017/S0080456800015982
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. doi.org/10.1017/S0080456800015994
xviBailey, L. (1964). The Isle of Wight disease: The origin and significance of the myth. Bee World 45(1):32–37. doi:10.1080/0005772X.1964.11097032
xviiWilfert, L., Long, G., Leggett, H.C., Schmid-Hempel, P., Butlin, R., Martin, S.J.M. and Boots, M. (2016). Deformed wing virus is a recent global epidemic in honeybees driven by Varroa mites. Science 351(6273):594-597. doi:10.1126/science.aac9976
vxviiiOliver, R. (2009). The learning curve: Part 4–The synthetic miticides. Scientific Beekeeping. https://scientificbeekeeping.com/the-learning-curve-part-4-the-synthetic-miticides/
Quigley, A. Editor of The Beekeepers Quarterly (pers. comm.).