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2021 in retrospect

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Déjà vu?

Well … not really.

This time last year I wrote my 2020 in retrospect post. Looking back the last few years I’ve always tried to post these retrospective reviews of the season a week or so before Christmas.

In December 2020 we had a rapidly rising number of Covid cases being diagnosed, peaking in early January at ~68,000 a day. One year later – actually a little less than one year – we’ve just surpassed those worryingly high numbers.

So, not déjà vu at all … as that means the feeling of having already experienced the present situation.

We have experienced it already 🙁

Like chalk and cheese

Covid and the lockdowns of 2020 had a dramatic impact on my beekeeping. I did the bare minimum to maintain the colonies. This involved little more than some rigorous swarm control followed by feeding them up for winter.

2021 has been completely different.

Despite the self-imposed restriction of living 150 miles from the majority of my bees, I had a really busy time and was beekeeping more or less all season.

And it was a very good season.

After a cold, late start to the year 1 I was concerned that the colonies weren’t going to be strong enough to exploit the oil seed rape and other early nectar.

Mean temperature difference in Spring 2021 from 20 year average

I needn’t have worried.

By mid May the colonies were booming and I managed the biggest spring honey harvest since returning to Scotland in 2015 2.

The honey bonanza was repeated again in the summer, again with a record crop.

What was particularly rewarding was that these good harvests were achieved from significantly fewer production colonies than previous years.

This isn’t really a case of Less is more, it just reflects what a good year it was here.

Downsizing

I had lived in Fife since 2015. From 2018 I’d spent increasing amounts of time on the west coast which – with lockdown – had included the majority of 2020.

Ardnamurchan sunrise, late November 2021

For many reasons this was preferable and, with no expectation of Covid (and all it had entailed) disappearing anytime soon, we took advantage of a brief hiatus in government restrictions 3 to sell-up in Fife and move permanently to Ardnamurchan.

The move was in February 2020 … and there are still some things that have yet to be unpacked.

The one thing I didn’t move was any bees.

Bees in Fife, like ~98% of the UK mainland, have Varroa. In contrast, the Ardnamurchan peninsula, together with some parts of neighbouring Morvern and Knoydart, are Varroa-free.

Therefore, in preparation for moving away from Fife altogether, I have been reducing my colony numbers on the east coast this year.

As many beekeepers know, the best way to do this is to split colonies into nucs and pop in a ripe queen cell.

Bingo!

Three weeks later you should have a mated queen and two to three weeks after that you will have a nuc ready for sale.

Have you seen the price of nucs recently?

All of which meant that I spent much of the first half of the season rearing queens.

Queen rearing in Fife

I probably enjoy queen rearing more than any other aspect of beekeeping.

I think I’ve previously recounted first reading Hooper’s Bees and Honey book and skipping over the queen rearing chapter thinking ‘Why on earth would I want to do all that?’.

Have you seen the price of nucs recently?

As Hooper said, there are few things more satisfying than working with a calm and productive colony headed by a queen you have reared.

And he was right.

Queen cells from grafted larvae … somewhere under all those bees

I started queen rearing on the 10th of May. In retrospect, despite getting good acceptance (10/10) of the larvae, this was a bit early as subsequent queen mating was patchy and slow.

If at first you don’t succeed …

The second and third batches of queens (on the 1st and 7th of June) were much more successful and the better weather in June improved mating success. Overall, almost 75% of grafted larvae resulted in mated queens.

In my experience, this is about as good as it gets. At least with my rather amateur fumbling.

I usually work with the expectation of getting about a 50% mated queens from larvae grafted, and am more than happy if I achieve much more than this.

Ben Harden setup and pollen patties

All of my cell raising in Fife used my favoured ‘Ben Harden‘ system which I described way back in 2014. I often supplement these with pollen but this year – as I had no stored pollen available – I used pollen substitute patties. There probably wasn’t a shortage of natural pollen but the bees still wolfed these down and I doubt they did any harm, even if they didn’t do much good.

Preparing a nuc for transport. Note the foam block to secure the frames

The resulting queen cells were added to 2-3 frame nucs for mating and then grown on.

In the good weather the nucs rapidly outgrew the boxes and I found myself stripping out frames of brood to hold them back when needed. The brood frames removed were used to boost production colonies, no doubt helping them collect a bumper summer crop.

West coast queen rearing

The season on the west coast starts later and develops more slowly than on the east. I suspect this is due to the absence of any oil seed rape, and possibly limited amounts of other early season sources of pollen and nectar.

Nevertheless, by late June I attempted my first round of queen rearing. With a patchy nectar flow – and despite feeding syrup – getting larvae accepted was tough. I also struggled to get the queens I did produce mated … although it wasn’t an unmitigated failure, it was in stark contrast to my experience on the east coast.

Beinn Resipol, early June

I’m pretty sure the poor queen mating success was down to a shortage of drones. This is a very sparsely populated area … of both people and bees. Next year I plan to boost drone production in all my good colonies, even if it’s at the cost of reduced honey production, to help populate the local drone congregation areas.

I used a Morris board for cell raising on the west coast. This works much like a Cloake board which I have used very successfully in previous years. I need a better season to determine whether it offers benefits over the Ben Harden setup.

Beekeeping is an exquisitely ‘local’ activity. Despite being at a broadly similar latitude and only ~150 miles apart, the bees in my east and west coast apiaries develop at different rates and swarm at different times. It’s probably going to take me a year or two to ‘get in the groove’ 4 with queen rearing on the west coast.

Record keeping

To help me remember what didn’t work last season – or to aid my recall of the few successes I did enjoy – I keep records.

In previous years I’ve done this with bits of paper that I carry around with me from apiary to apiary in my bee bag.

However, the combination of the house sale and my shockingly bad organisation 5 had resulted in me starting the 2020 season with no blank printed forms on which to keep records.

Colony records on a spreadsheet

I therefore cobbled together a slightly expanded version of the form on a spreadsheet and used this for all my record keeping.

I always have a laptop with me when travelling and the majority of my bees on the east coast are in apiaries with at least some shelter. Therefore, rather than taking notes and transcribing them to the spreadsheet I just typed them up, there and then, during the inspections.

The downs and ups of being a digital nomad

The N, M and comma keys are now sufficiently gummed up with propolis that the laptop is almost unusable.

D’oh!

The essential tech for the queen rearing digital nomad

However, keeping records like this has been a revelation. Not only are my records more complete than usual, they are also a lot more useful.

For example, they are directly searchable. If I search for ‘OA’ I can find the 18 instances when I referred to this during the year – all of which are in the Treatment column.

With a little Pivot Table magic I can see how busy I was during the season.

Colony inspections per week 2021

I’ve not broken this down into east and west coast apiaries, and I’ve exclude instances when the brood box wasn’t opened or when I did nothing but add syrup/pollen patties etc.

Over the season I inspected something like 340 colonies, but as is clear from the graph above, the bulk of the work was in May and June. Several colonies haven’t been fully inspected since late July, though all those on the east coast have had the Apivar strips added and removed.

Big deal … show me something useful

OK, I agree the graph above is of little use. Perhaps more beneficial is the ability to easily get an idea of various aspects of colony performance.

For example, when I’m queen rearing I only want to select larvae from my best colonies.

That’s not necessarily the colony I thought was best last week.

Perhaps I was particularly clumsy that week with an even better colony?

Maybe I have simply forgotten how psychotic the apparently good colony was in previous weeks?

It really should be the colony that has, over the range of characteristics I score, performed best over the season.

Come in number 21, your time is up

My queens are numbered, or at least the boxes they are in carry a unique queen number.

Therefore, by being careful not to duplicate queen numbers during the season, it’s possible to get an idea of which colonies (queens) have performed best … again with a little Pivot Table magic.

The scores are on the doors

These are cumulative averaged scores of three separate criteria e.g. temper or steadiness. I don’t keep records of honey weights, or longevity, or swarminess, or any number of other criteria … but I could if I wanted 6.

Next season I’ll have a pretty good idea which queens to select larvae from when I start queen rearing.

Mid-season scare

At some point late in July I received the dreaded ‘AFB within 5 km’ email from the National Bee Unit.

Irrespective of how careful you are in previous inspections, or of how rigorous you are with apiary hygiene 7, these emails are always worrying.

At least they are to me 🙁

I sold my first-borne child and purchased a load of AFB test kits, ordering them en route to Fife and collecting them from Brian in Thorne’s of Newburgh before arriving at the apiaries.

I then spent an entire day going through every frame 8 in every hive in the ‘at risk’ apiary and another site that I use.

Congratulations

It was a busy day.

After looking at a few hundred thousand cells you start to get paranoid.

Inevitably you’ll find a few partially capped cells … after all, they can’t go from open to capped without – at some point – being partially capped. I didn’t lateral flow test every one, but I did the ropey larva test on a large number … everything was negative.

Phew!

I was subsequently told that, although additional apiaries (one or more, bee inspectors are, rightly, careful not to disclose confidential information) were found with AFB, all were directly linked to the index site i.e. AFB transmission involved the beekeeper-mediated transfer of bees or contaminated equipment, rather than through drifting or robbing by the bees alone.

Forewarned is forearmed … next season I’ll be careful to check the colonies as they build up in the spring.

The dying of the light

I’m writing this as we approach the shortest day of the year which, here on the west coast, is about six and three quarter hours long.

There’s not much light, but what there is can be stunning …

Ardnamurchan sunset, looking towards Mull

It’s a good time to look back over the season.

To work out what worked and what didn’t.

Overall 2021 was pretty good as far as my bees were concerned. The season contained a normal range of surprising successes and abject failures, caused – in equal measure – by my usual insightful interventions and appallingly cackhanded meddling.

It was fun.

I learnt a few new things.

I probably re-learnt a lot more 😉

And, like every season, I saw things I’d either never seen before or not been alert enough to notice.

Herding drones

I’ll end this retrospective with a photo taken on the last day of August as I transferred a colony to a new brood box.

Herding drones

It’s not a particularly good photo as I had to carefully put down the frame I was holding and scrabble around for my camera.

In the far back corner of the hive, diametrically opposite the entrance (which was reduced to help the colony repel wasps), there was a ‘clump’ of drones. They were tightly wedged into the corner of the hive and – at least to me – it looked as though they were being herded there by the workers.

We all know that drones are evicted from the colony as autumn approaches.

Their job is done.

Actually, to be pedantic, if they are still alive in early autumn they have singularly failed to do their job 😉

Whatever … they are surplus to requirements as far as the colony is concerned.

Usually you see the drones being turfed out of the entrance of the hive.

I think this photo shows what happens to the drone inside the hive. The workers pester and harry them. Either they try and hide in the corners of the hive, or they are effectively herded there by the workers.

It can’t be a lot of fun being a drone in late August 🙁

 

Bee lining for Christmas

Bee hunting

Bee hunting

Following the Wild Bees† by Tom Seeley is an entertaining little book that would make an ideal Christmas present for a beekeeper. It describes the methods used to locate feral colonies (or any colonies actually) by bee hunting or bee lining, so called because you follow the line or direction they return to the colony from a nectar source you provide. It’s an ideal Christmas book for two main reasons; it’s a summer activity, so will remind the reader that balmy sunny days will – finally – replace the cold, dark days of winter and, secondly, it will allow the enthusiast the time to build the essential two-chambered ‘bee lining box’ which is used to trap, feed and mark the bees being ‘lined’.

I don’t intend to provide a précis of the method … you should buy and read the book for that. However, as a taster, you can visit the companion website to the book or watch a short video of Tom Seeley bee hunting …

Tom Seeley is a Professor in the Department of Neurobiology and Behaviour at Cornell University. He is a highly respected entomologist and, unlike many scientists, writes in an engaging and accessible manner. He explains complicated experiments in layman’s terms and makes parallels between his observations on honey bees and wider societal issues. Anyone who has read his book “Honeybee Democracy” will appreciate how simple and elegant his description of the science is.

His explanation of bee hunting is no less clear. Following the Wild Bees is really a ‘how to’ guide, rather than a popular science book, though each chapter does contain a separate section on the science behind the ‘how to’, together with lots of anecdotes. The book is subtitled “The craft and science of bee hunting”. If you’re not aware of feral colonies in your own area this book might help you find them … however, if you live in an area with lots of other beekeepers it will probably just help you find their apiaries (and you can also do that with Google maps).

Wild? They’re livid feral.

The most up-to-date review of feral colonies in the UK can probably be found in Catherine Thompson’s 2012 doctoral thesis (brace yourself … this links to PDF of the 173 page thesis!). Catherine surveyed a number of feral colonies in the UK and showed that, although there were limited but significant genetic differences between feral colonies and managed colonies, the feral colonies were no more ‘native’. Catherine also neatly demonstrates the limitations of studying wing veination (morphometry) as an indicator of genetic purity – it usually isn’t. Feral colonies are essentially relatively recent swarms lost by local beekeepers.

Why ‘relatively recent’?

High levels of DWV

High levels of DWV …

The feral bees Catherine studied had much higher levels of deformed wing virus (DWV), both indicative of – and as would be expected of – uncontrolled Varroa infestation. Therefore, whilst it might appear appealing to have colonies of wild bees in the local church tower they’re almost certainly riddled with DWV and Varroa. This presumably explains why so many of the feral colonies Catherine analysed died during the study period (2.5 years). The swarms lost by beekeepers (that occupy the church tower for example) quickly succumb to the detrimental effects of uncontrolled Varroa replication and the consequent transmission of viruses. Furthermore, through the activities of robbing and drifting that feral colony is likely to act as the generous donor of viruses and mites to the local managed beekeepers hives.

Perhaps not so appealing after all.

Conclusions

I recommend you read Following the Wild Bees. Do so sitting in front of a roaring log fire in mid-winter. Plan and build a ‘bee lining box’ (or buy one) and consider where you might go prospecting for ‘wild’ bees once the long summer days return.

But also plan to put out bait hives to catch swarms (yours or others) and clip your queens … every one ‘lost’ is an opportunity to establish a future source of Varroa and virus infestation.

Under offer ...

Under offer …

 

† ISBN-10 0691170266 … it’s worth shopping around for a copy as the prices vary widely (at the time of writing). WH Smiths had it for well under a tenner recently.

2015 in retrospect

The winter solstice seems like a good time to look back over the 2015 beekeeping year. With the day length about to start increasing, what went right and what went wrong? Back in March I wrote that my plans for the year were different from the usual OSR – swarming – queen rearing – summer flow – harvest – Varroa treatment – feed-’em-up and forget ’em routine as I was moving to Scotland in the middle of the season. Some of these things happened, though perhaps less than in a usual year.

Mid-season memories

Mid-season memories …

Spring – better late than never

Cloak board ...

Cloake board …

The OSR yielded poorly as the spring was cold and late. I didn’t even look inside a colony until mid-April. Colonies were only getting strong as the OSR flowers went over meaning that most of it was missed. The weather was unseasonably cold, with mid-May being 2-3ºC cooler than average. Queen rearing started in the third week of May and although grafting went well, queen mating was really hit and miss, with low temperatures and lots of rain lasting through May and June. On a more positive note, I used a Cloake board for the first time and was pleased with the results (I’ll write about this sometime in 2016 after using it a bit more). I didn’t use any mini-nucs this year as I didn’t want the hassle of dealing with them mid-season when moving North. Instead, I did all of my queen mating in 2-5 frame nucs, often produced as circle splits from the cell-raising colonies. This worked well … and considering the lousy weather was probably a lot less effort than using mini-nucs which would have required constant attention and lots of feeding. Using poly-nucs I could prime them with a frame of brood and a frame of stores and adhering bees, dummy them down and leave 3 frames of foundation (or wherever possible, drawn comb) ready to be used on the other side of the dummy board. Once the queen was mated the colony would build up well and if – as often happened this season – the queen failed to get mated or was lost (drowned?) during mating flights it was easy to unite the queenless unit with a queenright one, so not wasting any resources.

Go forth and multiply

Split board

Split board …

Beginners often find the coordination of colonies for queen rearing, and the apparent difficulty of grafting (it isn’t), a daunting prospect. When I’ve been involved in teaching queen rearing it’s clear that the relatively small scale approach I use (queenright cell raiser, grafting and – usually – mini-nucs) is often still too involved for the very small numbers of queens most beekeepers with just a couple of hives want. It was therefore interesting to raise a few queens using vertical splits, simply by dividing a strong colony vertically and letting the bees do all the work of selecting the best larvae, raising the queen and getting her mated. It has the advantage of needing almost no additional equipment and only requires a single manipulation of the hive (and even that can probably be simplified). Having documented the process this season I’ve got a few additional things I’d like to try in 2016 to make it even easier and to allow better stock selection. After that it will be incorporated into queen rearing talks and training.

Changes in Varroa treatment

The big change in Varroa treatment in the UK was the licensing of Api-Bioxal. Whether or not you consider the 50-fold or more cost of VMD-approved oxalic acid (OA) over the generic powder is justified is really a separate issue. Oxalic acid is an effective miticide and, if administered appropriately, is very well tolerated by the colony. Despite the eyewatering markup, Api-Bioxal is significantly less expensive than all other approved miticides. For the small scale beekeeper it’s probably only 20% the cost of the – often ineffective – Apistan, or either Apiguard or MAQS. Under certain circumstances – resistant mites, low temperatures or the potential for queen loss – there are compelling reasons why OA is preferable to these treatments. If we hadn’t been using OA for years the online forums would be full of beekeepers praising the aggressive pricing strategy of Chemicals Liaf s.p.a in undercutting the competition. Of course, if we hadn’t been using generic OA for years Api-Bioxal would probably be priced similarly to Apiguard 🙁

Sublimox in use

Sublimox in use …

I’ve used OA sublimation throughout 2015 and been extremely impressed with how effective it has been. Mite drops in colonies treated early in the season remained low, but increased significantly in adjacent colonies that were not treated. I treated all swarms caught or attracted to bait hives. Some were casts and there were no problems with the queen getting out and mated (though the numbers of these were small, so statistically irrelevant). Late season treatment of colonies with brood also seems to have worked well. Mite drops were low to non-existent in most colonies being monitored through late autumn. Colonies get mildly agitated during treatment with a few bees flying about under the perspex crownboard (you can see a couple in the image above … this was a busy colony) and a few more rapidly exiting the hive after the entrance block is removed. But that’s it. The colony settles within a very short time. I’ve seen no loss of brood, no obvious interruption of laying by the queen and no long-term detrimental effects. Sublimation or vaporisation of OA can – with the correct equipment – be achieved without opening the hive. I expect to use this approach almost exclusively in the future.

Moving bees

Moving colonies from the Midlands to Fife was very straightforward. Insect netting was an inexpensive alternative to building large numbers of travel screens. It’s the same stuff as Thorne’s sell for harvesting propolis so I’ve got enough now to go into large scale propolis production 😉 The colonies all settled in their temporary apiaries well and I even managed a few supers of honey during the latter part of the season.

Small hive beetle reappeared in Southern Italy shortly after the honey harvest was completed there. Che sorpresa. This was disappointing but not unexpected (and actually predicted by some epidemiologists). As I write these notes the beetle had been found in 29 Calabrian apiaries between mid-september and early December. It’s notable that there’s now a defeatist attitude by some contributors to the online forums (when not if the beetle arrives here) and – since not everyone are what they seem on the interweb – there are some playing down the likely impact of the beetles’ arrival (and hence the demand to ban imports) because they have a vested interest in selling early season queens or nucs, either shipped in or headed by imported queens. I don’t think there’s any sensible disagreement that we would be better off – from a beekeeping perspective – without the beetle, it’s just that banning imports of bees to the UK (admittedly only a partial solution) is likely to cause problems for many beekeepers, not just those with direct commercial interests. I remain convinced that, with suitable training and a little effort, UK beekeeping could be far less dependent on imports … and so less at risk from the pathogens, like small hive beetle. Or of course a host of un-tested for viruses, that are imported with them.

And on a brighter note …

Bee shed ...

Bee shed …

The new development in the latter part of the year was the setting up of a bee shed to house a few colonies for research. This is now more or less completed and the bees installed. It will be interesting to see how the colonies come through the winter and build up in spring. The apiary has colonies headed by sister queens both in and outside the bee shed so I’ll be able to make some very unscientific comparisons of performance. The only problem I’ve so far encountered with the shed was during the winter mite treatment by oxalic acid vaporisation. In the open apiary the small amount of vapour that escapes the sealed hive drifts away on the breeze. In the shed it builds up into a dense acidic hazy smoke that forced me to make a rapid exit. I was wearing all-encompassing goggles and a safety mask so suffered no ill effects but I’ll need an alternative strategy for the future.

Due to work commitments, house, office and lab moves, things were a lot quieter on the DIY front this year. The Correx roofs have been excellent – the oldest were built over a year ago and are looking as good (or as bad, depending on your viewpoint) as they did then. They’ve doubled up as trays to carry dripping supers back from the apiary and I’ll be making more to cover stacks of stored equipment in the future. Correx offcuts were pressed into service as floors on bait hives, all of which were successful.

With well-fed colonies, low mite counts, secure apiaries and lots of plans for 2016 it’s time to make another batch of honey fudge, to nervously (it’s got hints of an industrial cleaning solution) try a glass of mead and to finish labelling jarred honey for friends and family.

Happy Christmas

Lomond Hills and OSR

Lomond Hills and OSR

Miticide cost effectiveness

There goes a few pence ...

There goes a few pence …

My recent comments on the cost of Api-Bioxal prompted me to look in a little more detail at the cost of miticides routinely available to beekeepers. The figures quoted below are the best prices listed by one of three leading beekeeping suppliers in the UK (E.M. Thorne, Maisemore’s and C. Wynne Jones – there are lots of other suppliers, but I’ve used these three and been satisfied with their service). I made the following assumptions: the beekeeper is purchasing sufficient to treat three single-brooded full colonies for three years (i.e. something with a reasonable shelf-life) with as little left over as possible. Costs per colony treatment were calculated for 9 colonies (3 x 3 years) only … any ‘spare’ can therefore be considered as free. This means that for Apiguard, available in packs of ten trays (5 colony treatments) or a 3kg tub (30 colonies), the cost is calculated per colony from two packs of 10 trays as a full course of treatment for one colony requires two trays. Obviously, buying in bulk – for example through a co-operative purchasing scheme in your beekeeping association – should reduce these costs significantly. No postage costs were included.

Apiguard – two boxes of 10 trays (C. Wynne Jones) = £41 = £4.55/colony

Apistan – two packs of 10 strips (C. Wynne Jones) = £41 = £4.55/colony

MAQS – one 10 dose tub (all suppliers) = £57.60 = £6.40/colony

Api-Bioxal – one 35g sachet (C. Wynne Jones) = £8.20 = £0.91/colony

Oxalic acid (OA) crystals – one 300g tub (Maisemore’s) = £4.32 = £0.48/colony

Note that this simplistic comparison hides a number details.

  1. These various treatments should be broadly similar in their efficacy (see below) in reducing the mite population, but must be used according to the manufacturers instructions for maximum efficiency. Under optimal conditions all quote at least 90% reduction in mite levels. However, Apistan (and Bayvarol, not listed) is pyrethroid-based and resistant mite populations are very widespread. In the presence of totally or partially resistant mites, Apistan will be of little or no benefit. Interestingly, Apistan resistance (which, like resistance to pyrethroids in other species, is due to a single amino acid substitution, so readily selected) appears to be detrimental to the mite in the absence of selection. This means that it may be possible to use Apistan effectively every 3-5 years as part of an integrated pest management as long as other beekeepers in the area follow the same regime. During the years Apistan is not used the pyrethroid-resistant mites should reduce in number, so restoring the efficacy of the treatment. I’m not aware that this idea has been properly tested, but it might be worth investigating.
  2. Only the first four treatments are approved for use in the UK by the VMD.
  3. Both the oxalic acid-containing treatments – Api-Bioxal and OA crystals – require preparation before use, or specialised equipment for delivery. OA vaporisation (sublimation) also necessitates both care and personal protection equipment to prevent exposure to the chemical which is a lung irritant. The costs indicated do not include these additional requirements.
  4. The treatments are not equivalent or necessarily interchangeable. For example, a) only MAQS should be used when honey supers are present, b) Apiguard is moved around the hive by active bees, so treatment is recommended when average daytime temperatures are above 15ºC , and c) there are reports on discussion forums of repeated OA vaporisation treatment – 3 at 5 day intervals – for colonies with brood present. The costs indicated above assume a single treatment (in midwinter or of a swarm/shook swarm in the case of OA) with any of the listed compounds.
  5. Finally, the ‘excess’ amount spare after treating the colonies over three years differs significantly. The first four have sufficient left over for one further treatment. The OA crystals will have enough left over for a further 190 colonies … and buying a 300g tub is probably about the most expensive way to purchase OA per gram 🙂

Bang for your buck

As indicated above, all of the Varroa treatments listed should give 90+% knockdown in mite numbers if used properly. This means following the manufacturers’ instructions – in terms of dose, time and duration of application. A key point to remember is that the mite is only susceptible when outside the capped cell and that 80% or more of the Varroa in a colony at any one time will be inside capped cells if there is brood present. For this reason, it is preferable to treat during natural (or induced e.g. a shook swarm) broodless periods. It has even been suggested that the midwinter OA treatment should be preceded by destruction of any brood present. Although this makes sense, I can understand why some beekeepers might be reluctant to open a colony to destroy brood in the middle of winter. There have been numerous reviews of individual and comparative efficacy of the various Varroa treatments – for example this well-referenced article on mite treatment in New Zealand from 2008. If used properly there’s little to choose between them in terms of efficacy, so the choice should be made on the grounds of suitability, convenience and cost.

‘Suitability’ is a bit of a catch-all, but requires you broadly understand how and when the treatment works – for example, Apistan is a pyrethroid so works well against sensitive mites, but is pretty-much useless against resistant populations, and resistance is widespread in the UK. ‘Convenience’ is generally high in the ready-prepared commercial treatments – it takes seconds to insert a tray of Apiguard – and much lower if the compound has to be prepared or you have to get dolled up in protective gear. In this regard, the absence of a pre-mixed liquid version of Api-Bioxal is a disappointment. Thorne’s still supply (at the time of writing) Trickle 2, a very convenient pre-mixed 3.2% w/v OA treatment for mid-winter trickling, but for how much longer? Similarly, the gloves, mask, goggles and power needed to treat a colony by OA sublimation makes it far from convenient for a single treatment.

Closing thought …

1 lb jar of honey

1 lb jar of honey …

Despite the great differences between the cost/treatment/colony it’s worth noting that even the most expensive is not a lot more than the price of a 1 lb jar of top quality local honey … just like the stuff your bees produce 😉 So, in the overall scheme of things, Varroa treatment is relatively inexpensive and very important to maintain colony health and to reduce overwintering colony losses.

See also Managing Varroa (PDF) published by the Animal and Plant Health Agency

Sublime sublimation

Sublimox vaporiser

Sublimox vaporiser …

Sublimation is the conversion of a substance in the solid phase into the gas phase without going via the intermediate liquid phase. With suitable heating oxalic acid (OA) powder can be converted into a vapour which, when spread through the hive, provides a quick and effective way to reduce the mite levels … hence it’s often referred to as oxalic acid vaporisation (or vaporization … if you search the web on this topic you’ll find at least four variant spellings). With too much heating OA decomposes to formic acid and carbon monoxide, so the temperature of the vaporiser is critical to generate the optimal cloud of OA vapour (or vapor!). I’ve been using a Sublimox vaporiser this season with good results and provide a description of the machine and its use here.

Vaporisation vs dribbling

Most beekeepers are familiar with midwinter treatment with 3.2% OA solution (in syrup), applied by ‘dribbling‘ 5ml per seam across the clustered colony. Under these conditions the colony needs to be broodless as a) it’s not effective against mites in capped cells and b) the OA dissolved in syrup is toxic to brood. It’s also reported that the ingested OA may be suppress subsequent brood rearing, at precisely the time the colony should be getting started for the upcoming season. Vaporisation or sublimation avoids this toxicity … the OA is introduced to the hive as a gas which permeates the entire colony, recrystallising as tiny crystals on all surfaces – bees, comb, internal walls etc. Studies of OA vaporisation has shown it is ~95% effective in reducing phoretic mite numbers. I recommend you read the extensive coverage by Randy Oliver @ Scientific Beekeeping who covers efficacy, mode of action and toxicity (though I’ll return to this last bit later).

Sublimox vaporiser

This is an active vaporiser which blows a jet of vaporised OA through a small (8mm) nozzle. The machine consists of a handle, a box of electrickery (which I’ve not opened) and a heating pan surrounded with a safety guard. The machine is rated at 230V AC and 300W so you need either a car battery and inverter or a suitable generator (which is what I use). The vaporiser is simplicity itself to use. One gram of OA powder is placed into a small plastic ‘cup’, the preheated vaporiser is inverted and the ‘cup’ engaged with the heating pan. The nozzle is pushed through a hole in the hive body and the vaporiser is inverted again (so it’s now the correct way up – see the top photo on this page). The OA drops into the heating cup, immediately vaporises and is blown through the nozzle into the hive. It takes 40-50 seconds to use all the OA, at which point you can move on to the next hive.

This video shows the effect of dropping a few millilitres of water into the heating pan … it’s almost exactly the same when using OA, but less likely to cover my camera with a fine dusting of OA crystals 😉

Preparing the hive

Entrance block

Entrance block …

To fill the hive with vaporised OA it’s important that as little as possible leaks out during the short period of treatment. I use a Correx Varroa tray underneath the open mesh floor. In addition, the kewl floors I use are easy to block using a simple L-shaped piece of softwood (I use these when transporting hives; when screwed onto the front of the floor there’s no danger of bees escaping). Part of the beauty of OA vaporisation is that the hive does not even need to be opened. I’ve drilled 9mm holes just above the open mesh floor level, through either the side or back of my floors. This is a better location to insert the nozzle of the Sublimox as there’s space under the frames to allow the gas to spread evenly and quickly throughout the hive. This is easier than the alternatives of using an eke with a suitable hole in it, or drilling through the side wall of the brood box (this is too close to the frames and you get poor spread of the gas – I’ve tried this on hives with a perspex crown board and it’s very obvious).

With a standard floor you could use a simple entrance block with a suitable hole in it. The nozzle gets hot … keep it away from poly hives or nucs! I treat my Everynuc poly nucs directly through the (cavernous) front entrance which I block using a thick piece of wood with a 9mm hole through the middle.

Preparing the beekeeper

OA vapour is pretty unpleasant and causes significant irritation to the eyes and lungs if exposed. Take care. You will need suitable eye protection and a mask of some sort. I use standard (and very inexpensive) safety goggles and a 3M dust/mist mask. You should also wear gloves when handling OA. It’s also wise to stand upwind of colonies being treated and to take care not to breath in any OA vapour that leaks out of gaps in the hive.

In use

I’ve treated four swarms this year using OA vaporisation. Three had very low mite levels, but the small churchyard swarm dropped several hundred mites in the 2-3 days following treatment. I don’t routinely count the mite drop on each day post treatment (I have a life) but have noticed it can increase over the first 2-3 days and then tails off over the following week or so. In large scale studies in Europe 95% efficacy was reported with mite drop continuing for up to a fortnight. There are a number of useful references on the Scientific Beekeeping site if you want to follow this up further.

I’ve also used OA vaporisation on almost all my colonies this autumn, instead of Apiguard treatment. If the colony has sealed brood the usual estimate is that at least 80% of the mites are occupying capped cells. These mites are unaffected by OA vaporisation (until they emerge) and it is therefore necessary to perform repeat treatments. Taking account of the life cycle of the mite and empirical measurements made by Hivemaker reported on the Beekeeping Forum, three treatments at five day intervals are required to have the maximum effect. Ideally this should be on a day or at a time when most of the colony is ‘at home’ … though the crystallised OA continues to be effective for several days after initial treatment. Fortunately, OA vaporisation has little or no effect on the queen, unlike many other mite treatments. The colony gets mildly agitated during treatment but calms down again within minutes and resumes foraging. In the colonies I’ve looked at after treatment there appears to be no gap in egg laying (I’ve also treated casts with virgin queens that have gone on to mate successfully). This is ideal for the autumn treatment when you want the colony to raise as many bees for overwintering as possible. In contrast, Apiguard regularly stops the queen from laying.

And finally …

There are other OA vaporisers made, and instructions on the web for a variety of DIY items – some looking more dangerous (to the operator, not the mite) than others. The majority of these are passive vaporisers, in which the OA is placed in a cool heating pan which is then placed on the floor of the colony and heated up. I’ve not used this type. They have the advantage of being less expensive and only require a 12V supply. However, they are slower to use as the pan takes longer to heat up and then needs to be cooled in a bucket of water between applications. They are also incompatible with the kewl floors I use and I presume – depending on how hot they get – with poly hives and nucs. I think the efficacy of the two types is supposed to be broadly similar.

I listened to Bob Smith talk at the MSWCC conference last week on shook swarms. I sat there thinking that a shook swarm followed shortly afterwards by a single shot of OA vapour would give a colony a really good opportunity to build up well, free of pathogens that have accumulated in the comb and free of the majority of phoretic mites and their viral payload.

Economics

The Sublimox vaporiser is not inexpensive. It costs about €380 from Icko Apiculture. This is a lot, but is about the same as three 3kg tubs of Apiguard (C. Wynn Jones list this at £87 a tub at the time of writing) which is enough to treat 90 colonies with two treatments per colony. In contrast, OA dihydrate powder in bulk (not from Thorne’s) is about £20 for 5kg … enough for 1250 colonies (assuming 4 treatments per colony – 3 doses in the autumn and one midwinter). For beekeeping associations, particularly those with large shared apiaries when treatments could and should – see a later post – be coordinated, it might be a very good investment.