Tag Archives: bad beekeeping

Brexit and beekeeping

The ‘oven ready’ deal the government struck with the EU in the dying hours of 2020 was a bit less à la carte and a bit more table d’hôte.

The worst of the predictions of empty supermarket shelves and the conversion of Essex into a 3500 km2 lorry park have not materialised 1.

But there are other things that haven’t or won’t appear.

And one of those things is bees.

Bee imports

There is a long history of bee imports into the UK, dating back at least a century. In recent years the number of imports has markedly increased, at least partially reflecting the increasing popularity of beekeeping. 

Going up! Imports of queens, nucs and packages to the UK, 2007-2020 (National Bee Unit data)

Queens are imported in cages, usually with a few attendant workers to keep them company. Nucs are small sized colonies, containing a queen, bees and brood on frames. 

Packages are the ‘new kid on the block’ (in the UK) with up to 2500 per year being imported after 2013. Packages are queenless boxes of bees, containing no frames or brood.

Empty boxes after installing packages of bees

They are usually supplied in a mesh-sided box together with a queen. The bees are placed into a hive with frames of foundation and the queen is added in an introduction cage. They are fed with a gallon to two of syrup to encourage them to draw comb.

Installing a package of bees

It’s a very convenient way to purchase bees and avoids at least some of the risk of importing diseases 2. It’s also less expensive. This presumably reflects both the absence of frame/foundation and the need for a box to contain the frames.

But, post-Brexit, importation of packages or nucs from EU countries is no longer allowed. You are also not allowed to import full colonies (small numbers of these were imported each year, but insufficient to justify adding them to the graph above).

Queen imports are still allowed.

Why are were so many bees imported?

The simple answer is ‘demand’.

Bees can be reared inexpensively in warmer climates, such as southern Italy or Greece. The earlier start to the season in these regions means that queens, nucs or packages can be ready in March to meet the early season demand by UK beekeepers.

If you want a nuc with a laying queen in March or April in the UK you have two choices; a) buy imported bees, or b) prepare or purchase an overwintered nuc.

I don’t have data for the month by month breakdown of queen imports. I suspect many of these are also to meet the early season demand, either by adding them to an imported package (see above) or for adding to workers/brood reared and overwintered in a UK hive that’s split early in the season to create nucleus colonies.

Some importers would sell the latter on as ‘locally reared bees’. They are … sort of. Except for the queen who of course determines the properties of all the bees in the subsequent brood 🙁

An example of being “economical with the truth” perhaps?

Imported queens were also available throughout the season to replace those lost for any number of reasons (swarming, poor mating, failed supersedure, DLQ’s, or – my speciality – ham-fisted beekeeping) or to make increase.

And to put these imports into numerical context … there are about 45,000 ‘hobby’ beekeepers in the UK and perhaps 200+ bee farmers. Of the ~250,000 hives in the UK, about 40,000 are managed by bee farmers.

What are the likely consequences of the import ban?

I think there are likely to be at least four consequences from the ban on the importation of nucs and packages to the UK from the EU:

  1. Early season nucs (whatever the source) will be more expensive than in previous years. At the very least there will be a shortfall of ~2000 nucs or packages. Assuming demand remains the same – and there seems no reason that it won’t, and a realistic chance that it will actually increase – then this will push up the price of overwintered nucs, and the price of nucs assembled from an imported queen and some ‘local’ bees. I’ve seen lots of nucs offered in the £250-300 range already this year.
  2. An increase in imports from New Zealand. KBS (and perhaps others) have imported New Zealand queens for several years. If economically viable this trade could increase 3.
  3. Some importers may try and bypass the ban by importing to Northern Ireland, ‘staging’ the bees there and then importing them onwards to the UK. The legality of this appears dubious, though the fact it was being considered reflects that this part of the ‘oven ready’ Brexit deal was not even table d’hôte and more like good old-fashioned fudge.
  4. Potentially, a post-Covid increase in bee smuggling. This has probably always gone on in a limited way. Presumably, with contacts in France or Italy, it would be easy enough to smuggle across a couple of nucs in the boot of the car. However, with increased border checks and potential delays, I (thankfully) don’t see a way that this could be economically viable on a large scale.

Is that all?

There may be other consequences, but those are the ones that first came to mind.

Of the four, I expect #1 is a nailed-on certainty, #2 is a possibility, #3 is an outside possibility but is already banned under the terms of the Northern Ireland Protocol which specifically prohibits using Northern Ireland as a backdoor from Europe, and #4 happens and will continue, but is small-scale.

Of course, some, all or none of this ban may be revised as the EU and UK continue to wrangle over the details of the post-Withdrawal Agreement. Even as I write this the UK has extended the grace period for Irish sea border checks (or ‘broken international law’ according to the EU). 

This website is supposed to be a politics-free zone 4 … so let’s get back to safer territory.

Why is early season demand so high?

It seems likely that there are three reasons for this early season demand:

  1. Commercial beekeepers needing to increase colony numbers to provide pollination services or for honey production. Despite commercials comprising only ~0.4% of UK beekeepers, they manage ~16% of UK hives. On average a commercial operation runs 200 hives in comparison to less than 5 for hobby beekeepers. For some, their business model may have relied upon the (relatively) inexpensive supply of early-season bees.
  2. Replacing winter losses by either commercial or amateur beekeepers. The three hives you had in the autumn have been slashed to one, through poor Varroa management, lousy queen mating or a flood of biblical proportions. With just one remaining hive you need lots of things to go right to repopulate your apiary. Or you could just buy them in.
  3. New beekeepers, desperate to start beekeeping after attending training courses through the long, dark, cold, wet winter. And who can blame them? 

For the rest of the post I’m going to focus on amateur or hobby beekeeping. I don’t know enough about how commercial operations work. Whilst I have considerable sympathy if this change in the law prevents bee farmers fulfilling pollination or honey production contracts, I also question how sensible it is to depend upon imports as the UK extricates itself from the European Union.

Whatever arrangement we finally reached it was always going to be somewhere in between the Armageddon predicted by ‘Project Fear’ and the ‘Unicorns and sunlit uplands’ promised by the Brexiteers.

Where are those sunlit uplands?

And that had been obvious for years.

I have less sympathy for those who sell on imported bees to meet demand from existing or new beekeepers. This is because I think beekeeping (at least at the hobbyist level) can, and should, be sustainable.

Sustainable beekeeping

I would define sustainable beekeeping as the self-sufficiency that is achieved by:

  • Managing your stocks in a way to minimise winter losses
  • Rearing queens during the season to requeen your own colonies when needed (because colonies with young queens produce brood later into the autumn, so maximising winter bee production) and to …
  • Overwinter nucleus colonies to make up for any winter losses, or for sale in the following spring

All of these things make sound economic sense. 

More importantly, I think achieving this level of self-sufficiency involves learning a few basic skills as a beekeeper that not only improve your beekeeping but are also interesting and enjoyable.

I’ve previously discussed the Goldilocks Principle and beekeeping, the optimum number of colonies to keep considering your interest and enthusiasm for bees and the time you have available for your beekeeping.

It’s somewhere between 2 and a very large number. 

For me, it’s a dozen or so, though for years I’ve run up to double that number for our research, and for spares, and because I’ve reached the point where it’s easy to generate more colonies (and because I’m a lousy judge of the limited time I have available 🙁 ).

Two is better than one, because one colony can dwindle, can misbehave or can go awry, and without a colony to compare it with you might be none the wiser that nothing is wrong. Two colonies also means you can always use larvae from one to rescue the other if it goes queenless.

And with just two colonies you can easily practise sustainable beekeeping. You are no longer dependent on an importer having a £30 mass-produced queen spare.

What’s wrong with imported bees?

The usual reason given by beekeepers opposed to imports is the risk of also importing pathogens.

Varroa is cited as an example of what has happened. 

Tropilaelaps or small hive beetle are given as reasons for what might happen.

And then there are usually some vague statements about ‘viruses’. 

There’s good scientific evidence that the current global distribution of DWV is a result of beekeepers moving colonies about.

More recently, we have collaborated on a study that has demonstrated an association between honey bee queen imports and outbreaks of chronic bee paralysis virus (CBPV). An important point to emphasise here is that the direction of CBPV transmission is not yet clear from our studies. The imported queens might be bringing CBPV in with them. Alternatively, the ‘clean’ imported queens (and their progeny) may be very susceptible to CBPV circulating in ‘dirty’ UK bees. Time will tell.

However, whilst the international trade in plants and animals has regularly, albeit inadvertently, introduced devastating diseases e.g. Hymenoscyphus fraxineus (ash dieback), I think there are two even more compelling reasons why importation of bees is detrimental.

  1. Local bees are better adapted to the environment in which they were reared and consequently have increased overwintering success rates.
  2. I believe that inexpensive imported bees are detrimental to the quality of UK beekeeping.

I’ve discussed both these topics previously. However, I intend to return to them again this year. This is partly because in this brave new post-Brexit world we now inhabit the landscape has changed.

At least some imports are no longer allowed. The price of nucs will increase. Some/many of these available early in the season will be thrown together from overwintered UK colonies and an imported queen.

These are not local bees and they will not provide the benefits that local bees should bring.

Bad beekeeping and bee imports

If imported queens cost £500 each 5 there would be hundreds of reasons to learn how to rear your own queens. 

But most beekeepers don’t …

Although many beekeepers practise ‘passive’ queen rearing e.g. during swarm control, it offers little flexibility or opportunity to rear queens outside the normal swarming season, or to improve your stocks.

In contrast, ‘active’ queen rearing i.e. selection of the best colonies to rear several queens from, is probably practised by less than 20% of beekeepers.

This does not need to involve grafting, instrumental insemination or rows of brightly coloured mini-nucs. It does not need any large financial outlay, or huge numbers of colonies to start with.

But it does need attention to detail, an understanding of – or a willingness to learn – the development cycle of queens, and an ability to judge the qualities of your bees.

Essentially what it involves is slightly better beekeeping.

But, the availability of Italian, Greek or Maltese queens for £20 each acts as a disincentive.

Why learn all that difficult ‘stuff’ if you can simply enter your credit card details and wait for the postie?

Overwintering 5 frame poly nuc

Overwintering 5 frame poly nuc

And similar arguments apply to overwintering nucleus colonies. This requires careful judgement of colony strength through late summer, and the weight of the nuc over the winter.

It’s not rocket science or brain surgery or Fermat’s Last Theorem … but it does require a little application and attention.

But, why bother if you can simply wield your “flexible friend” 6 in March and replace any lost colonies with imported packages for £125 each?

Rant over

Actually, it wasn’t really a rant. 

My own beekeeping has been sustainable for a decade. I’ve bought in queens or nucs of dark native or near-native bees from specialist UK breeders a few times. I have used these to improve my stocks and sold or gifted spare/excess nucs to beginners.

I’ve caught a lot of swarms in bait hives and used the best to improve my bees, and the remainder to strengthen other colonies.

The photographs of packages (above) are of colonies we have used for relatively short-term scientific research. 

I’m going to be doing a lot of queen rearing this season. Assuming that goes well, I then expect to overwinter more nucs than usual next winter. 

I then hope that the bee import ban remains in place for long enough until I can sell all these nucs for an obscene profit which I will use to purchase a queen rearing operation in Malta. 😉

And I’m going to write about it here.


Notes

BBKA statement made a day or two after this post appeared. The BBKA and other national associations are concerned about the potential import of Small Hive Beetle (SHB) into the UK via Northern Ireland. Whilst I still think this breaches the Northern Ireland Protocol, it doesn’t mean it won’t be attempted (and there’s at least one importer offering bees via this route). It’s not clear that the NI authorities have the manpower to inspect thousands of packages.

It’s worth noting that SHB was introduced to southern Italy in 2014 and remains established there. The most recent epidemiological report shows that it was detected as late as October 2020 in sentinel apiaries and is also established in natural colonies.

With a single exception – see below – every country into which SHB has been imported has failed to eradicate it. As I wrote in November 2014:

“Once here it is unlikely that we will be able to eradicate SHB. The USA failed, Hawaii failed, Australia failed, Canada failed and it looks almost certain that Italy has failed.”

And Italy has failed.

The one exception was a single import to a single apiary in the Portugal. Notably, the illegal import was of queens, not nucs or packages. Eradication involved the destruction of the colonies, the ploughing up of the apiary and the entire area being drenched in insecticide.

The Beekeepers Quarterly

This post also appeared in the summer 2021 edition of The Beekeepers Quarterly published by Northern Bee Books.

Apivar (amitraz) resistance

Apivar is a widely used acaricide (a pesticide that kills mites and ticks) used to control Varroa.

The active ingredient of Apivar 1 is amitraz, a synthetic chemical discovered and developed almost 50 years ago.

Amitraz

Amitraz …

Amitraz has multiple molecular targets. I previously discussed the mechanism of action and summed it up with the words:

Essentially, amitraz binds and activates receptors that are critically important in a range of important aspects of the Varroa activity and behaviour … amitraz changes [this] behaviour and so exhibits miticidal activity. It has additional activities as well … these multiple routes of action may explain why resistance to amitraz is slow to develop.

I made the point in a subsequent post that amitraz resistance was very well documented … in cattle ticks 2 but that there was only anecdotal or incompletely documented evidence of resistance in Varroa in the USA, Argentina and Europe.

Apivar strip – fit and (don’t) forget

Amitraz has been used for mite control in honey bees for over twenty years. Considering its widespread use, the concentrations it is used at, and the relatively high replication rate of Varroa it is surprising that there has not been better evidence of resistance.

But that is no longer the case 🙁

Do you want the good news or the bad news first?

The bad news

A very recent paper 3 has clearly documented amitraz resistant Varroa in several commercial beekeeping operations in the USA.

I’ll discuss the key results of this paper first and then make some general comments on the implications for beekeepers and beekeeping.

The study had three components:

  1. Determine the sensitivity of Varroa never treated with amitraz to the chemical. This forms the baseline sensitivity against which field samples from commercial beekeepers could be tested.
  2. Screen Varroa from hives maintained by commercial beekeepers (with a multi-year history of Apivar usage) for amitraz resistance.
  3. Validate that the reduced efficacy of Apivar correlates with the observed amitraz resistance.

Essentially it involved harvesting live Varroa from colonies by a large-scale dusting with icing sugar 4. The Varroa were then tested to determine whether they showed resistance to amitraz, and the sensitivity was compared with the baseline sample of mites from colonies never treated.

Finally, an Apivar sensitivity test was conducted to determine the proportion of mites killed in a standardised assay in a set time period, again compared with the control (baseline sample).

The results of the study

You should refer to the paper for the primary data if needed.

Not all the apiaries tested yielded sufficient mites to screen for Apivar resistance. This is part of ‘the good news’ which I’ll get to shortly … but first the science.

Of those apiaries that did, Apivar resistance (determined by LC50 – the Lethal Concentration required to kill 50% of the mites) ranged from similar to that seen in the baseline samples to ~20-fold greater than the controls.

Two apiaries had an over 10-fold increase of the resistance ratio (the observed LC50 divided by the baseline LC50), with some individual colonies having high levels of Varroa infestation despite an active application of amitraz.

Apivar kills mites very quickly. Using a known number of mites trapped in a cage with a single small square of Apivar it is possible to ‘count the corpses’ and plot a kill curve over time. Sensitive mites from the control colonies were all killed within 3 hours.

Time course of Apivar efficacy in amitraz-susceptible Varroa

Using this as the baseline control it was then possible to determine the efficacy of Apivar in killing the mites (in the same 3 hour timeframe) from apiaries exhibiting resistance.

Apivar efficacy in commercial beekeeping apiaries.

Two apiaries (B and C, above) contained mites that exhibited high levels of resistance to Apivar, reflected in a low level of Apivar efficacy (above). In these apiaries, an average of less than 80% of mites were killed within the 3 hour assay.

Finally, the author demonstrated a correlation between Apivar efficacy and amitraz resistance. Unsurprising, but a necessary concluding point for the experimental data.

Within apiary variation

It was interesting that the author notes that the range of Apivar efficacy was much greater in colonies from apiaries with clear evidence of amitraz resistance.

For example, apiary B exhibited a range of Apivar efficacy in colonies from 28% to 97%, with an average (plotted above) of 68%. Whilst this is clearly an unacceptably low level, it is interesting that some of the colonies within the same apiary had mites killed at an efficacy similar or better (>90%) to apiaries A2 and A4 in the graph above.

I’ve re-plotted the primary data of Apivar efficacy vs. mite counts from individual colonies to emphasise this point.

Variation of Apivar efficacy vs mite infestation levels in individual colonies from commercial apiaries

Apiaries B and C (red markers) could be considered as ‘failing apiaries’ as the average Apivar efficacy of each was below 80% (see bar chart). Together the average mite load and Apivar efficacy for these two apiaries was 6.75 mites/100 bees and 72% respectively.

However, of the 16 colonies screened from these two apiaries (8 from each):

  • One colony had insufficient detectable mites to be included in the the full analysis.
  • Eight dropped less than 3 mites/100 bees during the sugar dusting analysis (the average over the 63 colonies screened was 5.33 mites/100 bees).
  • Four colonies exhibited ≥90% Apivar efficacy.
  • One colony from apiary B was a clear outlier, with >50 mites/100 bees ( 😯 ) and only ~28% Apivar efficacy. Inevitably this sample skews the averages …

Clearly the average figures presented in the bar chart above hides a very significant level of within-apiary variation.

Weird

I commented recently on the variation in mite levels during midwinter treatment of colonies with OA/Api-Bioxal. I attributed this – with little supporting evidence (!) – to different rates of late-season brood production. Colonies brooding late into the autumn were expected to have higher midwinter mite levels.

However, the variation seen here is different.

With the exception of that one heavily infested colony from apiary B, the mite levels in the ‘failing apiaries’ (B and C) are actually less than the average of the remainder of the study group (3.88 vs. 4.85).

What differs is the efficacy of Apivar treatment, not the resulting mite levels.

Frankly, this is a bit weird … on two counts:

  1. If Apivar treatment had been failing for a long time in apiaries B and C I would have expected much higher than average mite levels.
  2. Considering the amount of drifting and robbing that goes on between juxtaposed colonies I would have also expected Apivar-resistant mites to be very widely distributed within the ‘failing apiaries’.

Caveat on the mite counts – Apiaries in Louisiana, New York and South Dakota were analysed in this study. Louisiana apiaries were sampled in April, the others in July and August. I don’t know enough about the climate or mite-replication kinetics in these states to know how much this would have influenced the mite infestation levels (or prior or ongoing treatment regimes, which would also influence mite numbers). Unfortunately, the locations of the apiaries (A, B, C etc.) are not provided, other than the control apiary which is in Baton Rouge, LA. If the study had been done in the UK mite drops in April and August would have been wildly different depending upon the location.

Idle speculation

Apivar resistance does appear to have arisen in some of these colonies, but it does not appear to have become widely distributed within the apiary.

Why not?

I don’t actually think we have enough information to work with. The paper contains almost no additional background details – Apivar treatment history, use of other treatments, colony loss data etc.

But that won’t stop me speculating a little bit 😉

Do Apivar-resistant mites stop bees from drifting? Probably not, but it would explain why resistance was not widespread in the apiary 5.

More sensibly, perhaps Apivar resistance is detrimental in the absence of selection.

In the colonies in which resistance evolves it gives the mites a significant advantage. The ongoing infestation could encourage prolonged or repeated treatment, so selecting for yet more resistant mites. Eventually the colony succumbs to the resulting high viral load.

In other colonies, treatment is withdrawn (or forgotten … remember, we have zero information here!) and the Apivar-resistant mites are then at a disadvantage to their sisters.

This isn’t unheard of.

Apistan resistance appears to be detrimental in the absence of selection. There are some relatively straightforward molecular explanations for this type of phenotype.

You would have to assume differential colony treatments within apiaries B and C for this to be part of the explanation (and to account for drifting). Let’s hope the colony records are less shambolic than mine many beekeepers keep 😉

Until a clearer picture emerges of the management history of these colonies all we’re left with is the slightly (or very) confusing observation that Apivar resistance is a hive-specific phenomenon.

As the author states:

This colony level resolution suggests that each colony may act an island of resistance with its own distinct Varroa population. Beekeepers have reported inconsistency in amitraz treatment efficacy among colonies within an apiary and this variation seems to support those anecdotal observations.

And the good news?

I think there are two ‘encouraging’ observations in this paper (though of course I’d be happier if there was no resistance).

  1. About half of the commercial apiaries surveyed (5 of 11 that had a long history of Apivar usage) had too few mites detectable to screen for amitraz resistance. Clearly Apivar works, and often works very well indeed.
  2. Apivar resistance is not widespread in the apiaries within which it had arisen. For whatever reason, resistant mite populations appear restricted to individual colonies.

And these, in turn, have implications for practical beekeeping.

Implications for practical beekeeping

How does Apivar resistance evolve? Classically, misuse or overuse of treatments results in their eventual failure. Antibiotics are a good example of this.

I’ve been told by commercial beekeepers that some use a half dose of Apivar midseason to knock mite levels back sufficiently for the late season nectar flows. This is a typical example of misuse. It may not result in the development of resistance and it may not be a strategy used by the beefarmers managing apiaries B and C, but it is not the correct way to use Apivar.

What about overuse? Mites still dropping after 6 weeks of Apivar? Go on, slip another couple of strips in for another month or two. An (expensive) example of overuse.

Used Apivar strips

Or what about the Apivar strip found lying on the bottom of the hive at the first spring inspection? Again, overuse as there are likely to be lingering traces of Apivar present in the colony all winter 6.

So the first implication for practical beekeeping is to use Apivar correctly to help avoid the development of resistance. Don’t overdose or underdose, remove after 6-10 weeks, do not leave in over the winter.

Secondly, use alternate treatments to knock back the mite population. This is again a classic strategy to avoid selecting for resistance.

For example, use Apivar in late summer and Api-Bioxal in midwinter.

The mechanism of action of these two treatments is fundamentally different, so resistance to one will not confer resistance to the other (and there are no documented cases of oxalic acid resistance I’m aware of).

If you don’t treat midwinter (and you probably should 7) then use Apiguard one year and Apivar the next. Again, totally different mechanisms of action.

Finally, do not rely on individual colonies within an apiary being indicative of all colonies. I know some beekeepers who only conduct mite drop counts in one colony as a ‘sentinel’ 8.

If the drop is high then treatment is needed.

Or vice versa … no mites, so no treatment needed.

There’s a lot of colony to colony variation so it’s worth monitoring them all 9. And this is probably even more important with the colony level Apivar resistance reported in this paper.

Just something else to worry about … 🙁


 

Resistance is not futile

Apivar ...

Apivar …

Amitraz-containing miticides are sold in the UK as Apivar and Apitraz.

Until recently they were only available with a veterinary prescription. I expect – though I have not yet seen data to support this – that their usage in the UK will increase now they are off-prescription. These miticides are now widely available and so there is greater opportunity to use – and misuse – them.

If you’re using Apivar 1 for the first time this year you will soon have to remove the strips from the hive.

That’s assuming you started treating early enough to protect the all-important winter bees from Varroa and its deadly viral payload.

This post is a reminder to remove the strips at the right time. The alternative – leaving them in place until the first Spring inspections – risks help the development of resistance to amitraz, so further reducing our opportunity to control mites effectively.

Leave and let die

Without careful integrated pest management (IPM) 2 Varroa levels build up in the hive. Varroa transmits viruses – most important of which is deformed wing virus (DWV) – to developing pupae. High levels of DWV either kills the pupa or results in emergence with or without significant developmental defects. Even those bees that are apparently normally developed have a reduced lifespan 3.

Winter bees with a reduced lifespan prevent the colony from surviving through the winter until the queen starts laying again. I’ve also proposed recently that high levels of DWV, and the resulting increased rate of winter bee die-offs, probably accounts for some cases of isolation starvation.

So … intervention is needed to reduce mite levels, protect your bees and save your colonies.

Follow the instructions!

Apivar is one solution to reduce mite levels. It is an easy-to-apply chemical treatment that is very effective in reducing the Varroa load by ~95%. For a National hive it is applied as two polymer strips, each containing 500mg of slow-release Amitraz. Strips are hung between brood frames for 6-10 weeks and – for maximum efficacy – should be scratched with a hive tool and repositioned half way through the treatment period.

Amitraz

Amitraz …

Unlike some other miticides (e.g. Apiguard and MAQS) there are no temperature restrictions for Apivar usage. The colony does not need to be broodless (a requirement for trickled oxalic acid-based treatments) as the treatment period covers multiple brood cycles.

Other than not using it with supers present the only contraindication for Apivar is to not use it if Amitraz-resistant mites are present.

How does resistance develop?

When discussing parasites and pathogens, resistance 4 is a consequence of two things:

  1. A selective pressure that kills the pathogen
  2. A population which exhibits genetic diversity

The selective pressure could be anything … heat for example, antibiotics prescribed by your GP, an antiviral against HIV or – of relevance here – Apivar against Varroa.

Killing – at the population level – is not absolute. Some individuals within the population survive longer than others. They could be exposed to a slightly lower dose, or be located in a protected niche for example. However, treat for long enough and the majority will be killed.

But there’s more …

Pathogen populations are not genetically invariant. Actually, many are quite diverse and have replication cycles that – deliberately 5 – generate diversity.

Therefore some pathogens are genetically slightly less resistant and some are genetically slightly more resistant to a selective pressure. We can ignore the former as they’ll rapidly be killed off … but we must be concerned about the more resistant ones.

Keep taking the pills

All of this is a ‘numbers game’, better represented with graphs and equations. However, the take-home message is simple … to effectively control a pathogen you need to treat for long enough and with a high enough dose to kill the vast majority of the population.

That’s why you’re encouraged to “complete the course” of antibiotics … or to remove the Apivar strips after 10 weeks and not leave them in over the winter.

Because both courses of action result in selection of more resistant pathogens.

If you stop taking antibiotics too soon, you won’t have treated for long enough and with a high enough dose. You end up selecting for the more genetically resistant pathogens.

Similarly, if you leave Apivar strips in overwinter you’ll be “treating” the remaining mites 6 with a lower dose of the miticide, which is an ideal situation to favour the growth of the slightly more genetically resistant mites.

How does Amitraz resistance develop?

Resistance to Amitraz in Varroa is well documented. It’s been described in a number of countries including the USA and Europe, Mexico and Argentina 7. Generally resistance is defined in terms of a reduced level of mite killing, or – in laboratory experiments – an increased dose required to kill a certain proportion of mites.

However, I’m unaware of any studies defining the genetic basis of Amitraz resistance in Varroa.

But Amitraz is a widely-used acaricide 8 and the genetic basis of resistance in cattle ticks is well understood. In these, ticks resistant to Amitraz carry a mutation in the RMβAOR gene 9.

What 10 is the RMβAOR gene?

I’m glad you asked 😉

This gene encodes the β-adrenergic octopamine receptor protein and readers with good memories will recall that this is one of the targets that Amitraz binds to and inactivates 11.

If the protein carries a mutation the Amitraz cannot bind to it and so the mite – or more correctly the tick as it’s yet to be formally demonstrated in mites – is therefore resistant.

(Bad) practical beekeeping

What does all this mean in terms of practical beekeeping?

It means use the correct number of Apivar strips for the colony and leave them in for the right length of time.

Do not …

  • Use one strip on a full colony mid-season to ‘knock back the mites a bit’ 
  • Re-use the strips in another colony (yes really!)
  • Use improperly stored strips (or out of date strips) in which the effective Amitraz dose is reduced

I’ve heard examples of these types of misuse this season. All increase the chance of selecting for Amitraz-resitant mites.

And (the real reason for posting this at this time of year) …

  • Do not leave the strips you added in late summer in the colony throughout the winter

Removing the strips takes seconds. Prize off the crownboard, grab the tab projecting above the top bars, gently withdraw the strip and close the hive up again.

Finally, because of the incestuous lifestyle 12 of Varroa the genetic diversity (and therefore potential presence of more resistant mites) in the population is likely to be increased by the high mite levels that prevail late in the season.

All the more reason to use the effective treatments we currently have in a way that helps ensure they remain effective.


Colophon

Resistance is futile

Resistance is futile

Resistance is futile is the title of a 2018 album by the Welsh rock band the Manic Street Preachers.

More specifically, in the context of this post, it was the phrase routinely used by the Borg – the alien cyborgs sharing a collective mind – in the Star Trek franchise. Borgs rarely speak, but when they do they usually include this phrase. For example “We are the Borg. Lower your shields and surrender your ships. We will add your biological and technological distinctiveness to our own. Your culture will adapt to service us. Resistance is futile.” The warning about resistance being futile was usually accompanied by the threat that the target would be assimilated”.

I’d started writing this post using the title ‘Resistance is futile’ but realised late on that – as far as Varroa are concerned – resistance is anything but futile 13.

Resistance – to miticides – gives Varroa a reason to live. Literally.

Let’s not help them 🙂