Shook swarms and miticides

Synopsis : Combining a shook swarm with miticide treatment removes most mites in the colony and dramatically reduces DWV levels. The application of this strategy for practical beekeeping is discussed.

Introduction

Why does Varroa have such a devastating impact on colony health?

Feeding on haemolymph – or the abdominal fat body – by Varroa is probably detrimental. Furthermore, during feeding the mite induces immunosuppressive responses which make the bee both more susceptible to bacterial infections and compromises its nutritional status (Aronstein et al., 2012 1 ).

But if that wasn’t enough, the real damage is caused by transmission of viruses – in particular deformed wing virus (DWV) – from the mite to the developing pupa (and adult worker, as mites probably also feed on newly eclosed workers during the misnamed phoretic stage of the life cycle).

In the absence of Varroa, DWV is seemingly inconsequential for honey bees. Varroa-free colonies – including mine on the remote west coast of Scotland – carry DWV, but virus levels are very low and there is never any overt disease.

But Varroa infested colonies, particularly at this time of the season, often have very high levels of DWV.

Individual pupae parasitised by Varroa can develop stratospherically high DWV levels – reaching over a million times higher levels than seen in unparasitised bees (which can be similar to those recorded in Varroa-free bees). In the mite-exposed pupae the virus levels can kill the developing bees, or result in the characteristic symptoms (primarily deformed wings but also stunted abdomens and discolouration) that give the virus its name.

Worker bee with DWV symptoms

Worker bee with DWV symptoms

But bees not directly exposed to Varroa also have higher DWV levels in mite-infested colonies, particularly as the season progresses. Presumably this is due to horizontal transmission of the virus during larval feeding or trophallaxis.

What happens to these elevated virus levels after the removal of Varroa using a miticide such as Apivar?

Who cares? … I mean, Why could that matter?

The clue is in the section above.

Here it is again:

But bees not directly exposed to Varroa also have higher DWV levels [ … snip … ] presumably this is due to horizontal transmission of the virus during larval feeding or trophallaxis.

If you remove mites the virus levels in the treated adult bees are often surprisingly high 2. That makes sense because the miticide is only removing the vector for the virus … the bees with high levels of virus infection are unaffected.

If, during larval feeding or trophallaxis, these elevated levels of DWV result in yet more bees acquiring high DWV levels then the health of the colony will remain compromised.

The real reason that DWV is a problem for honey bees is that high levels of the virus result in the reduced longevity of bees. This isn’t an issue for the short-lived summer foragers 3. However, reducing the longevity of the winter bees – the so-called diutinus bees – can be fatal for the colony. These are the bees that support the queen in winter, thermoregulating the hive and that rear the first brood of the following season.

Their importance to successful overwintering cannot be overemphasised.

So, the question remains. What happens to the virus levels in the hive after the removal of Varroa?

Of course, the reason I’m posing this question is that we now know … 😉 .

Two easy-to-understand potential outcomes

It seemed to us that there were at least two likely outcomes.

  1. The virus levels in the hive drop very quickly after mite removal (red dashed line, below) and return to some sort of basal level. How quickly and to what basal level? We didn’t know.
  2. Virus levels remain elevated for a long period after Varroa is removed (red solid line, below). How long and to what elevated level? Yes – you guessed it – we didn’t know 😉 .

Of course, biology isn’t binary. There are any number of alternative outcomes … it’s just that those two seemed the most likely.

Two possible outcomes for virus levels after mite removal (black vertical dashed line)

What’s more, they’re the easiest to understand … and to explain.

Why might virus levels remain high if Varroa are removed?

Surely the short lifespan of adult bees means these would soon be lost from the colony … particularly if they have reduced longevity?

Yes, but …

We published a paper a couple of years ago that clearly demonstrated that honey bee larvae fed high levels of DWV became infected with the fed virus. The latter, which we could distinguish from any DWV already present in the larvae, replicated to similar high levels seen in a mite-infested hive (Gusachenko et al., 2020).

This observation perhaps suggested that the second scenario outlined above could occur. All the mites are slaughtered, but the remaining bees with high levels of DWV feed developing brood which consequently also go on to develop high levels of DWV.

Although it’s always good to remove mites this would not be the best outcome for the colony.

Virus quantification

Before I explain how we tested which, if any, of these two possibilities is correct I need to say a few things about virus ‘levels’.

For a variety of reasons I don’t have time, space or energy to explain, we don’t actually count viruses, instead we count copies of the virus’s genetic material (the genome).

All the magic happens in one of these machines – a Bio-Rad CFX96 Touch Real Time PCR system.

The virus genome is made of ribonucleic acid (RNA) and we can therefore use fantastically expensive sensitive and accurate diagnostic methods to measure how many copies are present in a particular sample – for example, in a worker bee, or a developing pupa.

Still with me?

Good.

To complicate things a little, we can’t meaningfully express the number of virus genomes present as an absolute number (like one million, or 2,478) because bees are different sizes; larvae are tiny, pupae are bigger, drones are larger still.

In addition, different workers are different sizes, larvae grow etc.

Therefore we express it as genomes per unit of total RNA extracted from the sample. That’s a bit of a mouthful, so we abbreviate it to GE / μg 4.

Phew!

And finally, to put some numbers on the low and high levels of DWV I discussed earlier, a bee from a Varroa-free colony contains ~1,000 – 10,000 GE / μg (103 – 104) of DWV whereas a pupa parasitised by Varroa regularly has 10,000,000,000 to 1,000,000,000,000 GE / μg (1010 – 1012).

That’s a lot of virus 🙁 .

The experiments

Experiments plural because we did these studies in both 2018 and 2019. ‘We’ are Luke (a then PhD student and now post-doctoral fellow in my laboratory, and the first author on the paper) together with our friends and collaborators, Craig, Ewan and Alan (in Aberdeen) and Giles (in Newcastle). The work was published a few days ago in the journal Viruses and is ‘open access’ (Woodford et al., 2022). This means that anyone feeling particularly masochistic or suffering from sleep deprivation can read all the gruesome details at their leisure.

Not ‘breaking rocks in the hot sun’ … but it sometimes feels like that

The paper covers more than just the one experiment I’m going to discuss here. We also looked at how the virus population changes when mite-free bees become infested with Varroa.

I’ll save that for another post 5  … it’s a good story in its own right.

Most mites are in capped cells

It’s been known for at least three decades that the majority of the Varroa population in a brood rearing colony are within capped cells, feasting on developing pupae.

Nom, nom, nom!

Precisely what percentage of the population is the majority varies a bit 6, but a figure of 90% is often quoted as typical for midseason.

% of mites in capped cells

The percentage of mites in capped cells (this is predicted, not actual data)

We reasoned that the best way to quickly remove all 7 the Varroa in a colony was to combine treatment of the phoretic mites with removal of all the brood … where the majority of the mites are lurking.

And to remove the brood (and associated mites) we conducted a shook swarm.

The shook swarm

Many beekeepers will be familiar with the technique called a shook swarm.

Shook swarm setup. Note Apivar strips in the open hive. Returning foragers already clustering at the entrance

This involves shaking all the adult bees into a new hive with frames containing fresh foundation. All the old frames and brood from the original hive are discarded.

We modified this by including Apivar strips in the hive into which we shook the adult bees.

Shook swarmed colony strapped up for transport … we wait for all the bees to enter the hive before moving it

The ‘shook swarm and miticide’ experiment – which we conducted in May – therefore involved the following steps (we used three strong double brood hives per season, each containing similar amounts of bees and brood):

  1. We quantified DWV in emerging brood in hives in which no Varroa management was conducted.
  2. The queen was removed, caged and kept safe for a few hours.
  3. All adult bees were shaken into a new brood box containing 11 frames of fresh foundation and two strips of Apivar 8.
  4. The shook swarms were relocated to a quarantine apiary.
  5. The queen was returned to the shook swarmed colonies and they were fed ad libitum with syrup to encourage them to draw fresh comb.
  6. Mite drop was recorded at 5 day intervals, increasing to longer intervals, until October when brood rearing ceased.
  7. DWV levels were quantified on a monthly basis from June to October.

As you can see, a very simple experiment.

The results

The mite levels in the ‘donor’ hives were much higher in 2019 than 2018. It’s not unusual to see this type of year to year variation in mite levels. In this instance the mean temperature in February and March 2018 had been several degrees colder than 2019 (remember the Beast from the East?).

The Beast from the East ...

The Beast from the East …

This almost certainly reduced early season brood rearing and so delayed mite replication. Brood rearing was strong by late Spring, but the mite levels in 2018 had yet to catch up.

The results of the experiment in both years were essentially the same. However, for clarity I’ll just present the 2019 data as the mite infestation numbers were so dramatic.

Mite drop after conducting the shook swarm

The cumulative mite drop from Apivar-treated shook swarms ranged from ~500 to ~3000 in the first 5 days. After that the daily mite drop remained at extremely low levels until recording stopped in October.

Mite drop following shook swarm and Apivar treatment

If you assume that only 10% of mites were phoretic at the time we conducted the shook swarm, this means that the total number of mites in some of these colonies was about 30,000. Even the colony with the lowest mite drop may have been hiding an additional 4,500 mites in capped cells.

Remember … the National Bee Unit guidance states that if mite levels exceed 1,000 then treatment is strongly recommended ’to avoid Varroa causing significant adverse effects to the colony’.

I think this part of the study shows just how effective Apivar is. After the first 5 days of treatment the cumulative drop – the Apivar strips still were left in place for 8 weeks – was extremely low for each fortnightly sampling period.

Of course – other than the very high numbers – none of this was particularly surprising. We know Apivar kills Varroa.

Perhaps you’re thinking ”My hives drop more Varroa during the autumn treatment, and for longer.”

When you treat a colony with brood present the mite drop is high in the first few days, but then often remains significant over the next 2-3 weeks while the mite-infested brood emerges. 

In our case, all the mites were on adult bees. By killing these mites in the first few days before there was new sealed brood in the colony we ensured the majority of the new brood did not become infested.

Virus levels before and after the shook swarm

In each colony we sampled a dozen emerging workers, once before the shook swarm and then on a monthly basis until brood rearing stopped. By testing emerging brood we could be certain they had been reared in the test colony, rather than drifting in from elsewhere. 

Before the shook swarm virus levels ranged from 105 to 1010 per worker, with an average of around 5 x 107 GE / μg. For those of you unfamiliar with scientific notation that is 50 million virus genomes.

Virus quantification in individual workers from colonies before and after the shook swarm and Apivar treatment

Strikingly, from the June sample onwards, virus levels dropped to an average of about 104 GE / μg (10,000 virus genomes, a 5,000-fold reduction). This average obscured a range of individual levels, from about 102 to 106.

These reductions are statistically significant … always reassuring 😉 .

The 2018 data showed a similar marked reduction in virus levels. The pre-treatment levels were marginally lower (remember, it was a ’low Varroa’ season), but the levels dropped to an average of only 1,000 GE / μg, a slightly higher fold-reduction and again highly statistically significant.

If you remove the majority of the Varroa the virus levels drop very fast to levels seen in mite-free colonies, or colonies with very low mite counts.

Tough love?

Some beekeepers consider that a shook swarm is tough on the colony. 

I’m not sure I agree.

How and when the shook swarm is done matters a lot.

It can be tough, but it shouldn’t be.

The bees need to draw new comb. For this they need ample feeding, lots of bees and warm weather. By conducting shook swarms on strong colonies in late May and giving them a few gallons of syrup we achieved all this.

‘I know I put that caged queen down here … somewhere’

Doing a shook swarm on a weak colony, too early (or late) in the season or omitting feeding is a recipe for disaster. The colony will struggle to draw comb, its brood rearing will be limited and it will be playing ’catch up’ for the remainder of the year.

Our shook swarmed colonies were booming by late July and entered the winter very strong. All overwintered successfully.

I’d argue that a shook swarm is a lot less tough on a colony than the disease burden caused by thousands of mites … 🙁 .

Why Apivar?

It’s worth emphasising that this was a scientific experiment to investigate the consequences for the virus population of removing almost all of the Varroa.

It was not designed as an example of how a beekeeper would necessarily choose to manage a honey production colony.

Our choice of Apivar was considered and deliberate. Application is straightforward, toxicity – at the levels we used – is undetectable and, critically for these studies, it remains active for weeks.

Apivar strip on wire hangar

Of course, Apivar cannot be used when there are honey supers on the hive 9. Any supers added for the summer nectar flow were not extracted.

Additionally, feeding gallons of syrup when there are honey supers present is also not recommended 😉 .

What else could we have used?

The two obvious choices were MAQS or oxalic acid. Both are effective against phoretic mites, though perhaps less so than Apivar. However, both are only active for a short period in the hive; the treatment period for MAQS is 7 days and the activity of oxalic acid – trickled or vaporised – is probably less than a week.

Neither could be relied upon to slaughter the maximum number of mites, a necessity to produce an understandable result 10. We were additionally concerned about problems with queens or absconding had we used MAQS (both of which would have invalidated the study), and we were keen to avoid the need for repeat treatments with oxalic acid (not least because this is not an approved application method).

With thousands of mites we wanted to ensure that the majority were killed quickly … and, as important, that any that survived the first few days of miticide treatment were also more than likely to be killed later 11.

Application to practical beekeeping

The main aim of this experiment was to investigate the levels of DWV in the colony after the majority of Varroa are removed. However, we were also mindful that the method may be useful for a beekeeper who discovers his/her colony has damagingly high mite levels mid-season, or for someone who inherits abandoned hives with high mite loads.

In these scenarios, assuming there are sufficient bees, some nice warm weather and lashings of syrup available, the combination of a shook swarm and simultaneous miticide application is probably the fastest way to restore colony health.

I am not suggesting that beekeepers routinely conduct a shook swarm and miticide application mid-season. It might not be tough on the colony, but that doesn’t mean it’s not very disruptive. If it’s not needed (because mite levels are well controlled, for example) then it’s a waste of brood … and syrup.

However, there are times when I could imagine it might be useful.

If your primary crop is heather honey you’ll know that the hives sometimes don’t come back from the hills until late-September. That’s late to be applying miticides to protect the winter bees. In an area with an extended June gap (which often starts in May) it might be possible to effectively rid the hives of Varroa in June and have a strong colony to take to the moors in early August.

This is probably a better approach than using a half dose of Apivar in June (as some do) which probably doesn’t kill all the mites anyway, risks contributing to amitraz resistance in the mite population and may result in Apivar strips being left in the hive during the heather flow 12.

Conclusions

Miticides kill mites … big deal.

However, it’s the viruses – in particular deformed wing virus – that kill colonies.

We have now shown that removing the majority of the mites from a colony (including those associated with sealed brood) results in the levels of DWV in the hive dropping very quickly.

The speed with which this happens – four weeks or less – is probably accounted for by the lifespan of the adult bees in the colony following the shook swarm.

This suggests that high levels of virus are not horizontally transmitted or (and this is subtly different) that horizontal transmission, through feeding, of large amounts of virus does not result in elevated levels of virus replication in the recipient bee (larva or adult).

All sorts of questions remain. Would oxalic acid be a suitable replacement for Apivar? How much virus is transferred from a worker to a larva during brood rearing, or between workers during trophallaxis? Is this below a threshold for efficient infection? Do virus levels drop as dramatically when treating a broodless colony (e.g. after caging the queen for three weeks)?

In the meantime just remember that ”the only good mite is a dead mite” … and, if you kill the mites, you also quickly reduce virus levels to a level at which they do not damage the colony.

And a straightforward way to achieve that is to combine a shook swarm with an effective miticide.

Result!


References

Aronstein, Katherine A., Eduardo Saldivar, Rodrigo Vega, Stephanie Westmiller, and Angela E. Douglas. ‘How Varroa Parasitism Affects the Immunological and Nutritional Status of the Honey Bee, Apis Mellifera’. Insects 3, no. 3 (27 June 2012): 601–15. https://doi.org/10.3390/insects3030601.

Gusachenko, Olesya N., Luke Woodford, Katharin Balbirnie-Cumming, Ewan M. Campbell, Craig R. Christie, Alan S. Bowman, and David J. Evans. ‘Green Bees: Reverse Genetic Analysis of Deformed Wing Virus Transmission, Replication, and Tropism’. Viruses 12, no. 5 (May 2020): 532. https://doi.org/10.3390/v12050532.

Woodford, Luke, Craig R. Christie, Ewan M. Campbell, Giles E. Budge, Alan S. Bowman, and David J. Evans. ‘Quantitative and Qualitative Changes in the Deformed Wing Virus Population in Honey Bees Associated with the Introduction or Removal of Varroa Destructor’. Viruses 14, no. 8 (August 2022): 1597. https://doi.org/10.3390/v14081597.

 

 

Footnotes

  1. Remember … posts now contain a proper reference list at the end. Fill yer boots!
  2. Perhaps 10,000 to 100,000 times higher than mite-free bees.
  3. Actually, formally we don’t know this. As I showed in a recent post there is a class of experienced elite foragers that do the majority of the nectar and pollen gathering for the colony. If these were lost it may be detrimental to the nutrition of the colony.
  4. genome equivalents per microgram
  5. You can have too much of a good thing.
  6. For reasons that I’ll maybe explain in another post as it is important in quantifying mite levels from the mite drop.
  7. Formally, almost all … for reasons I’ll definitely cover in another post. Generally miticide treatment reduces (massively) but does not eliminate mites from the colony.
  8. The ‘discarded’ brood frames were distributed to other hives in the ‘mite-infested’ apiary.
  9. Or rather, it can be, but the honey is tainted and cannot be used for human consumption. If I have supers like this I store them safely and put them underneath a strong hive in the autumn to supplement the winter feeding.
  10. I’m assuming you’ve not read the paper in full or you might argue with this statement.
  11. Preferably slowly and painfully …
  12. This was flagged as an issue by the Scottish Government Bee Inspectorate a couple of years ago.

24 thoughts on “Shook swarms and miticides

  1. Frank Lindsay

    What a great article. Compulsory reading for new beekeepers to understand mites and viruses.
    I hope you won’t mind but I’ll save this and use it as additional material for new beekeepers.

    Frank Lindsay
    Wellington
    New Zealand

    Comment: how do you get time to put out a post each week.
    It takes me weeks to put together a newsletter for our beekeeping group
    I’ll send you a copy.

    Reply
    1. David Post author

      Many thanks Frank

      It’s usually not too much of a problem producing a post each week. The secret is no TV, limitless coffee and a willingness to work a 29 hour day 😉

      The purpose of this post is to emphasise that if you get rid of the mites, the viruses are no longer a worry (at least, DWV isn’t … until, of course, the mite numbers build up again). In the past I think there was an assumption that this was the case, but assumptions can be wrong. Having done the experiment, and knowing that most beekeepers aren’t avid readers of the journal Viruses (I can’t for the life of me imagine why not) it seemed sensible to try and present it in an easier to digest format.

      Cheers
      David

      Reply
  2. Iain Dewar

    Another great article David, and a timely reminder that those wee pests just won’t go away, and of the costs of forgetting to carry out effective varroa controls.

    Reply
    1. David Post author

      Thanks Iain

      They don’t go away … but you can encourage them and, done at the right time, you can achieve low mite numbers and reassuringly low virus levels. Most beekeepers cannot measure the latter, but the results in this recent paper show that one follows the other. Look after the mites and everything should be OK.

      I’m off to remortgage the house so I can buy some Apivar 😉 *

      Cheers
      David

      • that’s a joke (as you well know) … I’m going to write something about the false economy of scrimping on miticide treatment at some point. For a well-managed hive in a reasonably good environment I reckon the mite treatment per annum costs perhaps 1-2% of the potential ‘profit’ from the hive. Only profit if you sell honey and bees, but the overall figures are about right.
      Reply
  3. Alan Jones

    A lot of food for thought, David. I have been reading about going treatment free and thought I would try it with half of my hives, treating the home apiary with Apivar and then everybody in December with vapourised OA and counting the difference in mite drop, but after reading your post I am beginning to lose my nerve!!!
    Cheers
    Alan

    Reply
    1. David Post author

      Hello Alan

      The cumulative drop of the treated-in-autumn colonies vs. the post-OA drop from harshly ignored and abandoned (was that laid on a bit thick?) untreated colonies may not be too different. After the autumn there’s not a huge amount of brood for the Varroa to reproduce in.

      However, the difference is likely to become apparent in winter survival … if not this winter, then next. If you treat in midwinter with OA then; a) make sure you do it during a brood free period, and b) I guess it’s not really treatment-free 😉

      Post an update if/when you try this.

      Cheers
      David

      Reply
  4. Mel Robertson

    But surely Formic Pro kills mites in the capped brood as well as on the adult bees- would this not eliminate the need for a shook swarm?( especially if used later in the season for the preparation of winter bees)

    Reply
    1. David Post author

      Hello Mel

      Yes, Formic Pro kills mites under the cappings, but that wasn’t the point of this study. We weren’t testing the miticide, we were exploring what happens to the virus after removing all the mites. And the best way to do that is the way we did it.

      We chose Apivar because it is probably the most effective miticide (90-95% killing) and, coupled with the shook swarm, it would allow us to remove all the mites in 1-3 days. That in turn would allow us to investigate the impact on the virus population of – more or less overnight – removing the main route of virus transmission.

      I’ve recently had reason to read some of the scientific studies on Formic Pro. There are some oddities about the mite drop after application. This is high for a day or two – presumably killing the phoretic mites – and then it drops to low levels, and remains that way. What happens to all those mites in the capped cells (which could be 50-90% of the mite population) that Formic Pro is supposed to kill? Why don’t they appear on the tray? I’ve not used MAQS or the other formic acid-containing treatments so haven’t observed this myself.

      Finally, note that Formic Pro is reported to weaken the colony and is associated with significant levels of queen loss (up to 40% in some of the published studies). Neither is ideal for late season treatment.

      Cheers
      David

      Reply
  5. Ian Turley

    Have you looked at other viruses, eg CBPV. Do you think this would be an alternative method to destruction?

    Reply
    1. David Post author

      Hello Ian

      We haven’t. However, it wouldn’t help with CBPV as it’s not a brood disease and is also not transmitted by Varroa. We are looking at CBPV in collaborative studies, but are concentrating on prevention, not cure.

      Cheers
      David

      Reply
  6. Ian Turley

    Ok great. As a (old and rusty) biochemist interested in how do you determine what varroa transmits. Do you use varroa genome analysis or other method. Think I need to do some back reading 🙂
    Ian

    Reply
    1. David Post author

      Hello again Ian

      Brenda Ball did some of the early work on CBPV and showed it was not associated with Varroa; see Ball, B. V., and M. F. Allen. 1988. The prevalence of pathogens in honeybee (Apis mellifera) colonies infested with the parasitic mite Varroa jacobsoni. Ann. Appl. Biol. 113:237–244. She also convincingly demonstrated that direct contact of virus onto the cuticle resulted in transmission. Ribiere (2007) subsequently showed it was transmitted via honey bee faeces suggesting contaminated wooden ware might be a source of infection. Our studies have shown that incidence of CBPV infections are increasing significantly.

      I wrote a little about CBPV a couple of years ago …

      Cheers
      David

      PS You’re not the only one behind in your reading 😉

      Reply
  7. Vince Poulin

    David – one more method to consider – if there are not enough! Let me update you on Queen Exclusion Trapping. I’m using this thread because I do not get notices of your replies so often lose my way on earlier posts. But if you recall I built 4-queen exclusion traps that are similar to the commercial one you showed me last year. Nice design actually. On July 21 I caged queens in 3-hives (N=3) and July 23 an additional queen N=1). Today I inspected the 3 exclusion traps cages on July 2.. Result #1 – queens in all traps laid-up what appears a good % of the available drone cells (Warre sized frames) on the trap frames. Result #2 and this is an important one – all queens survived my handling. I found it a bit tricky capturing a queen and placing her in a trap and closing it without risk of damaging her. Practice helps. One of the traps contains a frame of what looks like fully capped cells making it a candidate for removal tomorrow and replacement of the frame to re-start the cycle. I will give the other 2 frames another several days to ensure each frame is filled as much as possible. Result #3 all hives are lacking uncapped brood and no queen cells. When all uncapped cells outside the traps hatch I will have forced all mites in the colonies to become phoretic. This will take another 12 or so days – give it 15 and I’ll be at mid-August and will at that time have at least 2-drone traps filled and all mites not trapped phoretic. At that time I will ensure all honey is removed and I’ll hit the hives with OA. I have one additional hive that is set up similarly but a Lang hive with large frames. With no suitable trap I used a Warre trap (4 of 4). For that hive I took a medium super and designed a very cool internal trap that I think you will enjoy seeing and of course if it works well. It’s consists of queen excluder built into the walls of the hive box and capped top and bottom to contain the queen. Much less fussy a trap than the ones you saw me build in spring. Anyway – one great experiment with little to no down-side. Adult bees continue gathering honey, no chemicals, and the ability to collect right up through to end of the trapping period.

    Reply
    1. David Post author

      Hello Vince

      All sounds very promising. Are you going to treat twice with OA or just once? Vaporised or trickled? When the bees are distributed rather than clustered I prefer to vaporise OA, not least because I can seal the hive late in the afternoon and know there are no foragers out working carrying mites that would otherwise likely escape treatment.

      I know what you mean about handling queens … yesterday, after clipping and marking dozens and dozens over the years I fumbled things badly and she flew off. My excuse was that it was very hot, I’d been taking honey off some hives and was tired, there was a huge amount of propolis in the hive (and all over my gloves) and – and this is probably the real reason – I wasn’t concentrating 🙁 I just closed the hive up and will hope for the best. Usually the Q returns (she was mated from the hive, so knows where it is). However, this late in the season, knowing my luck, there will be queen cells when I next check. If that’s the case I’ll unite the colony. Getting a queen mated here that late can work, but not reliably.

      Cheers
      David

      PS You should get the option to subscribe to comments (separately to getting new post announcements) when leaving a comment. Relatively few readers do.

      Reply
      1. Vince Poulin

        I do click all those option but for some reason I don’t get the notices. I would value that but they don’t despite clicking “Notify me of follow-up comments by mail”. I do get notices of your new posts weekly – that one works! I understand you predicament with queens and sticky gloves. For the first time I hauled out a bucket of soapy water and washed gloves every time I went to move a queen. This time of year propolis is extremely sticky, I imagined a queen glued to a glove. “Stuff happens”. Your queen will be back. Yesterday I entered the hive containing Trap #4. The queen was healthy but only laid up say 20% of the available drone cells. Despite that I moved her into the new cage set-up. This is a medium super where I routed slots to take queen excluder on either side of 2-medium frames. The bottom is solid wood – the top had queen excluder cut to fit the width of the 2-frames. I placed the queen inside and closed up the hive. For some odd reason – the frame I used in the Warre sized trap – the one with 20% drone cells without thinking I placed in an adjacent NUC to become fully capped!!!! Duuh! Why I did that explains how easy for”Stuff to happen”. This is after recharging the 3 other hives with new comb for the queen to lay up and leaving those frames in their respective hives to do what they were supposed to do – Trap mites!. So back again this morning. The story gets potentially crazier. I opened the hive. Got to the queen exclusion trap but decided not to disturb it. I just brought that one drone comb back and placed it where I should have done yesterday. All good. Closing up the hive I decided to take a quick check around the new queen exclosure. I pulled a frame two spots left of the trap and WHAT? There was a marked queen. She somehow got out of the new trap. HOW? I gathered her up and dropped her once again down inside the trap and carefully replaced the top. I closed up the hive. Driving home a sense of panic struck me. Yesterday I joined two hives. I removed the queen (marked) and placed the rejected queen in a frame box. Ha!!! That box went with me yesterday to the apiary where Trap #4 was going to be emptied. While there I decided to release the queen. I placed her on a lovely flower but she quickly took to the sky. I never thought twice we were miles away from her home. Then just before leaving we see a pile of bees cluster on the grass. All excited almost as if attacking something. Indeed – there was the marked queen. She didn’t fly far but in the grass. I brushed the bees off and she took flight again. So????? Is it possible that queen was the one I found inside the hive today?????????????? Could she have gone into a thriving hive of 40,000 bees and survived to make it up through a brood box and find herself 2-frames away from the queen exclosure???? Because that never ever occurred to me the queen I found outside the exclosure is the one I dropped back in the trap. Ha, think about it – maybe. If so – I’ll know soon as I will be checking the trap in about 5-days time. What a hoot. “Stuff happens”. We can only laugh but with your operation your brain has to be 200% occupied just doing apiary work – on top of that the research, writing and effort to produced weekly posts. Being 100% occupied is bad enough.

        Reply
        1. David Post author

          Hi Vince

          Interesting story about the queen returning. I’m afraid I cull queens that I don’t want for that very reason. They can fly better than many people think and the last thing I want is for her to turn up unannounced in the hive she came from (or, for that matter, in another hive).

          Of course, having now stated that ‘they fly better’, the one that flew off last weekend will never be seen again, despite the fact she only had a couple of metres to go to the hive entrance.

          Stuff happens!

          Cheers
          David

          PS I suspect I need to burrow into the database to find out which discussions you follow. I’ll check when I have time and see if I can fix things. However, since there’s always the risk of destroying the entire site due to my hamfisted SQL abilities it might take some time 😉

          Reply
  8. Marcus Hughes

    Hi David,

    Thanks for another informative article, backed by some proper science. I noticed it says ‘newly enclosed workers’ in the parentheses at bottom of para. 3 in the introduction. Should that read ‘newly emerged workers’?

    Cheers

    Marcus

    Reply
    1. David Post author

      Hi Marcus

      Grrrr … that’s a spellcheck error on my part. It should read ‘newly eclosed workers’ where eclosing is the term used to describe an insect leaving its pupal case. Emerged would do instead, but the spellcheck wouldn’t have made the same correction.

      That’s what comes of making the last few edits on my laptop rather than my desktop. All fixed now.

      With thanks
      David

      Reply
  9. David L

    Hi David,

    At last! I went looking for some guidance on the rate of viral load decay after I found a colony with DWV last September (Apivar delayed due to a strong balsam flow) and wanted to maximise the speed at which the viral load decayed before winter. In the end I did nothing other than watch the persistsnt mite drop and fret, but I think I can thank the strong ivy flow for giving me time to get a healthy brood cycle through before winter.

    Anyway – I’m curious about the complications you’ve added to your experiment with the shook swarm aspect. Yes, you get the mite load to almost zero in days, but you also removed contaminated combs and induce a short brood break I’d have thought the brood break in particular could be significant because you’re cutting off the supply of newly emerging bees which would otherwise be feeding young larvae within days.

    How do you distinguish what of the recovery is due to mite removal vs the other changes in colony dynamics induced by the shook swarm?

    … Or should I just go read the paper? 😂

    Reply
    1. David Post author

      Hello David

      Removing brood simplifies the study of the drop in virus levels. Without doing that there’s the possibility of brood emerging over the following 18 days (or 21 with drones; calculated by development time minus time as an egg) with variable amounts of virus. We only screened emerging brood that – by definition – were produced after doing the shook swarm. Had we left the brood in we’d have had to determine whether the brood was old or new … and if it was old, what would that have told us as it may well have been parasitised and have high virus levels.

      As far as I’m aware this is the first study of virus load after miticide treatment. It shows what’s possible under – albeit artificial – ideal conditions that were designed and expected to have the maximum impact on the mite population, and therefore presumably have the maximum potential impact on the virus levels.

      It’s now for someone else to study virus levels following treatment without brood removal, or to investigate the changes in viral load induced by an enforced brood break. Both would be interesting things to investigate. Both will take time, people and money. To be informative it should include multiple hives and at least two separate years.

      Perhaps the miticide manufacturers should fund this? After all, removal of mites is effectively a surrogate for what is really needed which is reducing the damaging levels of DWV in the hive.

      Cheers
      David

      PS If you read the paper you’ll also see what happens to the virus levels in an (almost) mite-free hive if you don’t treat and allow mite infestation. It’s not pretty 🙁

      Reply
  10. Ian Robinson

    Sorry for late comment – just playing catch up on reading Anothe good blog thanks and I have the paper still to attempt!

    I was interested in your comments on the application to practical beekeeping. Were there any observations of colonies making preparations to swarm before or after the process or did the shook swarm suppress this. Just wondered if this approach may be an additrional benefit to the mite/virus control since most people have to do some form of swarm control anyway.

    Thanks

    Reply
    1. David Post author

      Hello Ian

      None of the colonies were making swarm preparations when we did the shook swarms and none needed any swarm control in the same season. A shook swarm is a pretty dramatic change of circumstances for a colony. It’s not directly comparable to a natural swarm as all the adult bee population are present in the shook swarm, whereas a natural swarm has a significant bias towards the younger bees. However, the ‘discarding’ of all the brood means coupled with the box containing no drawn comb means the colony pretty much has to start again from scratch. Despite feeding them well for about three weeks (they draw comb really fast) the brood break clearly holds them back for a significant period. We weren’t interested in their subsequent nectar gathering activity (and didn’t record numbers of supers and/or their weight for example).

      I don’t doubt that it might at least delay swarm preparations, but that might be at a significant cost in terms of honey produced. I suspect this depends upon the precise timing of the shook swarm.

      We did the experiment to formally test how fast virus levels reduce. Since this is the real goal of mite reduction it seemed odd that it had never been measured. In terms of practical beekeeping, I see it as a useful method to rescue a badly infested colony mid-season.

      In terms of swarm control and coupled mite control, it’s worth noting that careful use of something like the nucleus method can produce brood-free periods in both the queenright and queenless ‘halves’. These can be treated with oxalic acid to reduce mite levels if needed. Timing is critical and the way you make up the queenright nuc is very important, but it is achievable. I’ve written about this in midseason mite management.

      Cheers
      David

      Reply
  11. Ian Robinson

    Thanks for your comments and thoughts about nucleus methods for brood free periods. I will reread the midseason mite management post. Best wishes

    Reply
    1. David Post author

      Remember … any form of swarm control where you separate the Q and a frame of emerging brood (or unsealed brood) works … e.g. a Pagden artificial swarm. The key point is to be selective in the frame you accompany the queen with.

      Cheers
      David

      Reply

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