Category Archives: Practice


Excuse me?

Hydroxymethylfurfural which, for very obvious reasons is usually abbreviated to HMF, is an organic compound that forms in sugar-containing foods, often as a result of heating.

Hydroxymethylfurfural (HMF) Oxygen = red, Hydrogen = white, Carbon = black

HMF is relevant to bees because, at high levels, it is toxic for them. Since beekeepers often heat (or use ready-made feed that has been heated during production) sugar-containing syrups or fondants it’s worth being aware of it.

HMF is also relevant to beekeepers as high levels of it in honey are an indication of prolonged heating during storage and preparation or potential adulteration. For this reason there are legal limits on the levels of HMF in honey sold for human consumption.

I suspect beekeepers in the UK who know about HMF – and many may not – probably worry about it unduly. In tropical countries or regions where high fructose corn syrup is used as a bee food then HMF is likely to be of more immediate importance.

Natural occurrence of HMF

Hydroxymethylfurfural is essentially absent from fresh foods. However, in sugar-containing foods, particularly those that are acidic, HMF levels can build up. A chemical process called a Maillard reaction is responsible for HMF formation (there are other reactions that generate HMF as well, including caramelisation) and the reaction works about five times faster for every 10°C rise in temperature.

Therefore processes such as drying or cooking result in elevated HMF levels. The precise amount varies depending upon the foodstuff, the amount of heating and other factors; typical figures are bread 3 – 180 mg/kg, prunes 240 mg/kg, sugarcane syrup 100 – 300 mg/kg and roast coffee 900 mg/kg 1.

All of these foods can be consumed perfectly safely (at least in terms of their HMF content … prunes can have some adverse effects 😉  ).

It should therefore be obvious that the 40 mg/ml limit 2 of HMF in honey has nothing to do with its safety for human consumption.

Dietary HMF has been extensively studied as there were concerns it may be carcinogenic for humans. Several studies showed that non-physiological levels and/or prolonged exposure were cytotoxic or inhibited key enzymes in the cell such as DNA polymerase. However, no evidence for in vivo carcinogenic or genotoxic effects have been demonstrated 3.

HMF is currently considered safe and has been shown to have beneficial antioxidant activity, to protect against hypoxic (low oxygen) injury and to counteract the activities of some allergens.

HMF in honey

Readers familiar with the chemistry of honey will be aware that it is often rich in fructose (one of the sugars from which HMF is derived) and is acidic.

Add a little heat and you have near-perfect conditions for the production of HMF.

How much heat? 

It’s actually not just heat but a combination of heat and time.

The higher the temperature, the less time is required for the production of a certain amount of HMF. There are several studies of this, but one of the most frequently quoted is from White et al., in 1964 4 which has this slightly skewwhiff, but nevertheless useful, graph of the influence of storage temperature and time on HMF production in honey.

HMF production in honey – influence of storage temperature and time

That’s barely legible – check (and enlarge) the original if needed – but the approximate times/temperatures required to generate 30 mg/kg of HMF in honey 5 are as follows:

30°C ~250 days
50°C ~10 days
70°C ~10 hours

All of which is good news … heating a 15 kg bucket of rock-solid OSR honey overnight at 50°C to melt it before making soft-set honey is unlikely to significantly increase the HMF levels.

How to avoid the generation of HMF in honey

But, if you are worried about HMF levels, you could always produce creamed honey which just requires overnight warming at 33°C.

This is what I now do; not because of any concern over the HMF levels but because it’s:

  • faster
  • produces a honey with better batch-to-batch consistency of texture
  • generates a jarred honey much less susceptible to frosting

Long-term storage of honey results in the formation of HMF. The lower the temperature it is stored (and the shorter the time) the less HMF is produced. For an exhaustive list of HMF levels quantified in honey stored at different temperatures have a look at Table 1 in Shapla et al., (2018).

Store honey carefully in a cool place … or sell, eat or gift it quickly

It makes senses to store honey in a cool place with a relatively stable temperature.

Quantifying HMF

There are a variety of ways of detecting HMF. Unfortunately, all require laboratory equipment and none are really suitable for home use.

There are spectrophotometric methods – essentially detecting a colour change after adding an indicator that reacts to the presence of HMF – but these can lack both sensitivity and specificity. Some of the chemicals involved are carcinogenic.

More accurate and sensitive are methods use reversed-phase high-performance liquid chromatography. These have been in routine use for years.

Orbitrap ID-X Tribrid Mass Spectrometer

Probably the newest and most advanced methods involve the use of time-of-flight mass spectrometry (MS MALDI-TOF). These ionise the constituents of the sample and measure the time they take to reach a detector. Mass spectrometry is exquisitely sensitive and specific … and the equipment is eye-wateringly expensive. 

Since you’re unlikely to have one in your honey processing room 6 you’re better off doing your best to avoid conditions that lead to the build-up of HMF in the first place.

OK, enough about honey and humans, what about the bees?

HMF is toxic for both adult bees and developing larvae. The level of toxicity depends upon the concentration of the HMF, the duration of exposure and the developmental stage of the bee.

Krainer and colleagues 7 looked at toxicity of HMF to developing larvae and showed that concentrations up to 750 ppm (i.e. 750 mg/kg) did not reduce larval or pupal mortality.

Larval and pupal mortality when exposed to HMF at different concentrations.

They calculated that the LC50 (concentration that produced 50% mortality) at day 7 and day 22 was 4280 ppm and 2424 ppm respectively, with a calculated LD50 (dose per larva that resulted in 50% mortality) of 778 μg and 441 μg at day 7 and day 22 respectively.

Adult bees were less sensitive to HMF in the first week after emergence than during the first week of larval development.

Adult bee mortality when fed a diet containing HMF at the levels specified

What does all this mean?

It means that high levels of HMF are likely to have a significant impact on adult bees, but – at least until the levels are exceptionally high (grams, not milligrams, per kilogram) will probably not adversely impact brood levels.

Further validation of the adverse effects of HMF to adult bees

A similar study was recently conducted by Gregorc and colleagues 8 using lower concentrations of HMF.

Survival of adult bees fed with HMF-spike Apifonda

Again, there was a time/dose response, but note that only about 30% of the control bees survived 30 days and this was only double the number that had been fed the lowest level of HMF-spiked Apifonda. Note the clear evidence of a dose-response with increasing levels of HMF in the diet.


Several studies, dating back at least 50 years, report that high levels of HMF result in dysentery-like symptoms due to ulceration of the gastrointestinal tract of honey bees.

Gregorc and colleagues used immunohistochemistry to investigate the integrity of the gut tissues in the honey bees fed HMF. They stained cells red that were undergoing a process called ‘programmed cell death’ or apoptosis. This is a natural physiological response to damage. The more red staining, the worse the damage.

Midgut of formalin-fixed, paraffin-embedded tissue of worker bees exposed to HMF

At higher doses of HMF and/or longer exposure there was increased apoptosis in the gut tissues, presumably accounting for the dysentery-like symptoms often seen (though these were not recorded in this particular study).

Real world beekeeping

All of these bee corpses and fancy-dan immunohistothingamajiggery really just confirm that high levels of HMF are a bad thing™

In terms of honey processing and storage the allowed levels are nothing to do with human (or bee) health, but everything to do with evidencing overheated, poorly stored or doctored honey.

And since no readers of this blog do these things then there’s no need to be concerned 😉

Assuming your honey starts with low HMF levels (on extraction) then any reasonable levels of heating to liquify honey for filtering, blending or jarring should not result in HMF levels anywhere near to those that would prevent the honey being saleable 9.

Refer to the graph above from the 55 year old paper from White and Co. (shown above) for further validation.

If you’re making thick (2:1 by weight sugar to water) syrup to feed bees perhaps use warm rather than boiling water. However, considering the time involved and the absence of the acidity of honey, even with the latter HMF levels should not get close to high enough levels to endanger the bees.

If you’re making thin (1:1 by weight) syrup then use cold water. Just stir it a bit longer to dissolve it all.

However, take care – or avoid altogether – the use of high fructose corn syrups (HFCS) for feeding bees. I don’t know anyone who does this in the UK and have no experience of it myself. To learn more have a look at this article in Bee Culture. HFCS is high in fructose (the clue is in the name) and acidic, so HMF readily forms.

Studies of commercial HFCS show levels of HMF can start at 30 – 100 mg/kg before any long-term storage. 

Oxalic acid

The only time most beekeepers probably need to have concern about HMF levels is in the preparation and storage of oxalic acid solutions for trickle treating colonies in midwinter.

Oxalic acid is, er, acidic. For trickle treating it’s mixed with thin syrup to make a 3.2% solution. The combination of syrup and acidity means that HMF can be produced if stored – for a long time – in unsuitable conditions (under which there is an obvious colour change).

Stored OA solution and colour change

Stored OA solution and colour change …

So, if you’re preparing OA solutions for trickle treating either:

  • use it immediately and safely dispose of the excess
  • store it at 4°C and use then it as soon as possible (before safely disposing the excess)


But what about fondant?

The HMF levels in commercially available fondant have recently been discussed on the Beekeeping Forum. I’m grateful to ‘loyal listener reader’ (to use Radio 4’s More or Less definition) Archie McLellan for bringing this to my attention.

The thread started with the challenging title The truth behind fondants.

Like all discussion groups, the contributions are many and varied.

Some wander off-topic.

Others use it as an opportunity to get a little dig in at the opposition.

Or a great big dig 😉

Novices and the naive ask simple questions and hope for straightforward answers 10.

Usernames often give no indication of who the poster actually is.

Is the poster a manufacturer or distributor of BeeCentric fondant™ “The best fondant for bees and a whole lot better than that cr*p they sell for ice buns”

Does the poster use 5 tonnes of fondant a year and buys anything s/he can get as long as it’s cheap enough?

Or does the contributor have a £576,000 Orbitrap MALDI-TOF mass spectrometer in their basement and a damned good idea of exactly how much HMF is present in every commercial source of fondant?

On the internet, nobody knows you’re a dog

Who knows?

I certainly don’t know all of the contributors to these threads.

But I know some of them 😉

Read the thread. It’s now 12 pages long and you’ll do well not to get lost or to disappear down a few cul-de-sacs

If you’ve ‘got a life’ and want to cut to the chase then have a look at this post in particular.

What do I do?

I use standard Baker’s fondant. It costs about £8-12 for 12.5 kg depending how much you need. I’ve used this type of fondant for a decade for 90% of my colony feeding (and 100% of my autumn feeding).

I’ve never seen any adverse effects from using this type of fondant for my bees.

I simply do not believe some of the negative marketing that is used to promote BeeCentric fondant™ costing £36 for 12.5 kg. It’s not that I can’t afford this 11 and it’s certainly not because I don’t care about my bees. I simply choose to trust experience over carefully-worded marketing ‘information’.

To convince me they’d need to publish the HMF levels in their products. They might be lower than bog-standard Baker’s fondant.

And I’d also want to know the HMF levels in standard Baker’s fondant 12.

If they were significantly higher 13, are they anywhere near high enough to damage my bees?


A version of this article appeared in the November 2021 edition of An Beachaire – The Irish Beekeeper.

Winding down

Here in Scotland the season is rapidly drawing to a close. All of the summer nectar sources – the lime, blackberry and heather – have stopped yielding and the bees are noticeably less busy, other than in the warmest parts of the day.

Inside the hive the colony is segueing from summer to winter bee production. Brood rearing is still ongoing and there’s lots of pollen still going in, but the rate at which the queen is laying is very much reduced.

And, as the bees transition from summer to autumn behaviour, my own beekeeping activities are also changing. No more queen rearing, uniting or even colony inspections. The risk of swarming ended months ago.

Instead, with the winter ahead, the number of evening talks is increasing and several winter beekeeping projects are starting to occupy my mind.

But the season’s not over yet and there are still a few last minute tasks before active beekeeping stops. Here is what has been keeping me busy over the last week or two …

Talk, talk

Beekeepers are a sociable bunch and the pandemic has had a significant impact on the amount of digestive biscuits consumed and tea slurped in church halls across the country.

However, in addition to being sociable 1 they are also adaptable and inventive. Zoom and GoToMeeting talks, attended from the comfort of the sofa with a glass of red wine, have become the new normal. 

Early forays into the world of ‘virtual’ beekeeping were plagued with dodgy connections or noisy feedback.

Q&A sessions were stilted due to the lack of familiarity with the need to unmute the microphone before talking.

Some were more like a Marcel Marceau tribute act than Beekeeper’s Question Time.

But all that has changed.

I’ve experienced some excellent hosting, lively and interactive Q&A sessions and entertaining pre- or post-talk chat with beekeepers across the country. 

‘Virtual’ beekeeping talks

Increasingly this format appears to have been widely accepted. There may not be face-to-face meetings with tea and biscuits, but there’s also no need to drive half way across the county on a filthy, wet winter night.

Long distance talks – imagine the travel expenses being saved

I live in one of the most westerly locations in the UK (I’m about 15 km west of Land’s End) and have used the title ‘Go West young man’ a couple of times in previous posts. Later this winter I’ll be ‘virtually’ going west a further 7000 km and talking to beekeepers in British Columbia, Canada. They may be half way across the world, but their climate (reasonably mild and wet) is not dissimilar to the west of Scotland, and bees are bees 🙂 

It should be interesting.

Zoom and GoToMeeting

About 95% of the talks I give (or attend) use Zoom. It works well. The interface is logical and I can see some/all of the audience. Questions are often handled through the ‘Chat’ function. At least a couple of associations have invested in an add-on 2 that allows questions to be upvoted, so moving the most popular or relevant topic 3 to the top of the pile. 

‘Seeing’ the audience in the talk isn’t really necessary, and can be a bit distracting 4. But I find it really helps during the Q&A session, and certainly makes the ‘virtual’ interaction just that little bit more realistic. 

At the very least I can guesstimate the age and experience of the beekeeper asking the question, so allowing me to tailor my answer if appropriate. Of course, this sometimes goes wrong, but people are usually too polite to point out my error.

GoToMeeting is less intuitive (possibly because I’ve used it less) and I don’t think offers me a view of the audience 5. However, I think it’s more suited to larger audiences and coped admirably with ~250 who attended a recent talk to the Welsh BKA.

OK, enough virtual beekeeping … what about the real thing?

Heather honey

In the six years I lived in Fife (on the east coast of Scotland) I never moved my bees outside a 20 mile corridor in the centre of the county. The arable farmland, mixed woodland and low, rough grazing contained no (worthwhile) heather.

Therefore, despite living in Scotland, I’ve no previous experience with heather, considered by many to be the ultimate honey. However, on the west coast we have patchy heather on the hill behind the house, so the bees have almost no choice but to forage there.

After a record-breaking honey yield in Fife, anything extra in the west was a bonus.

I was singularly ill-equipped to extract it. A few of the frames I put through the extractor collapsed spectacularly, so I was reduced to scraping the frames back to the midrib and crushing and straining the honey out.

As I’ve said before, there’s always something new to learn.

Crushed and strained … I was, but I got there eventually

And I learnt that this can be a messy and exhausting process 🙁

One of many few … my first jars of Ardnamurchan honey

But, by golly, it was worthwhile 🙂

I now have to buy a larger shed to store a compressed air-driven fruit press as extracting anything more than half a dozen supers of heather honey will probably drive me round the bend.

Based on the price of these fruit presses and the likely honey yield per year I reckon I’ll break even in about 29 years 🙁  6

The heather here on the west coast goes on yielding long after the bees in Fife have packed up and gone home.

At least, usually. 

Feeding and forage

The summer honey came off the hives in Fife in mid-August. All the colonies were treated with Apivar strips and received a full block of fondant on the same couple of days I removed the supers.

It was hard work, not least because there was a lot of honey. All the supers were brought back home for extracting, and subsequently returned for storage.

As described a couple of weeks ago, I only feed fondant in the autumn. Having checked the colony is queenright I simply plonk a block of fondant on the hive and leave them to get on with it 7.

When I checked the colonies earlier this week all had completely finished their 12.5 kg fondant block.

All gone

Although I didn’t do a full colony inspection, I did have a peek in a couple of hives to check the level of stores and brood. They were wall-to-wall with capped stores except for 2-3 frames in the centre of the brood box which contained about a hands-breadth of brood. Much of this brood was capped and there was still a little bit of space for the queen to lay … but not much.

However, several boxes also had brace comb in the super above the empty bag of fondant. None of this contained brood as I always support the block of fondant on a queen excluder. 

Bees don’t draw comb on fondant … or do they?

I suspect this comb building was triggered by the availability of ivy nectar. In previous years I’ve not seen comb drawn when feeding fondant. However, it’s been quite mild and the bees have probably been taking advantage of the warm weather to supplement the fondant.

Avoiding another sticky mess

I don’t want to leave the bees with a third of a super of ivy honey, particularly when the rest of the super is a big empty space they would have to heat. However, I also don’t want to mess about cutting it all away or – worse – wasting all their efforts.

A small hole

Therefore, having removed the queen excluder and the empty fondant wrapper I placed a new crownboard and empty super back on the hives with brace comb. I modified the crownboard to reduce the hole to about a single bee width.

Regular readers will know that modified almost always means either gaffer tape or Correx.

I’ve branched out this time and instead used the side of a cardboard box of fondant for one hive. If this works I’ll claim it was a well thought out experiment. If it doesn’t I’ll claim I was pushed for time and had no Correx or gaffer tape with me 8.

Having done all this I added back the original crownboard with the attached brace comb and closed the hive up securely.

The intention here was to make the stores in the brace comb appear as though it was outside the hive. I expect the bees to relocate the nectar from the brace comb – none of it was capped yet – to the brood box, as and when space become available.

No top ventilation please

Finally, reinforcing the point I made recently about the dislike bees have for top ventilation, every single Abelo crownboard “vent” was gummed up solidly with propolis. 

I’ve got the message loud and clear. No matchsticks needed here.

Scratch and sniff reposition

Apivar strips need to be placed in the edges of the brood nest, at least two frames apart and in diametrically opposing corners of the hive.

But in mid-August the brood nest is a lot larger than it is a month later. As the brood nest shrinks, the strips get further and further away from the main concentration of the bees in the hive.

In an active hive stuffed with bees this probably isn’t a major issue. However, to achieve maximum exposure of the bees – particularly the young bees that Varroa like to hang out with and that are concentrated around the brood nest – it makes sense to reposition the strips midway through the treatment period.

Apivar strip placement as the brood nest shrinks

Apivar treatment takes 6-10 weeks. The actual wording is something like “The larger the brood is, the longer the strips should be left in the limit of 10 weeks”. I usually treat for 9-10 weeks; my colonies are all pretty strong at the end of the summer.

But strips left for that long in the hive often get gummed up with propolis and wax.

Apivar strip efficacy is probably impaired by all that propolis and wax

I therefore spend a few minutes scraping the strips clean of gunk 9 and then reposition them in the hive, adjacent to the – now shrunken – brood nest.

There are studies showing that this scratching and repositioning of the Apivar strips marginally increases the devastation wreaked on the mite population.

Apivar scratch and sniff repositioning studies

And that can only be a good thing™.

More heavy lifting

I returned to the west coast after two long days of driving, beekeeping and meetings 10 having collected a further 125 kg of fondant en route. 

The following day a pallet of jars were delivered from C Wynne Jones. I get the square jars I like – and, more importantly, my customers like – from there. Because of my remote location the ‘free delivery’ comes with a hefty surcharge, so it makes sense to buy a reasonable number at once.

Unfortunately the courier transported them on a 36 ton artic, and there was slightly less than no chance whatsoever that it would be able to negotiate our ~300 metre, 1 in 5 driveway.

I’d had a barely decipherable call (wrong mobile network) from the driver in the morning as he arrived on the peninsula but heard nothing more. I presumed he was still negotiating the ~18 miles of single track road to get here.

Either that or he’d got no phone reception.

I was right on both counts.

He knocked at the door having been unable to call me, but had abandoned the lorry in the road and walked up the hill to the house. 

What a star.

With thanks to Palletline

In exchange for a jar of honey – to restore his flagging blood sugar levels – he unloaded the pallet in the road and I made four trips by car to collect the boxes.

Beekeeping is a high-volume pastime 11 … everything takes up a lot of space.

I think I need to find another location for the canoe that occupies one side of the shed.

In between all the heavy lifting …

And canoeing with the dolphins in the loch is the other thing I’ve been enjoying now the majority of the beekeeping is winding down for the year.


Cut more losses

This is a follow-on to the post last week, this time focusing on feeding and a few ‘odds and sods’ that failed to make it into the first 3000 words on reducing overwintering colony losses.

Both posts should be read in conjunction with one (or more 1 ) of my earlier posts on disease management for winter. Primarily this involves hammering down the mite levels before the winter bees are produced, so ensuring their longevity.

But also don’t forget to treat your colonies during a broodless period in midwinter to mop up mites that survived the autumn treatment, or have reproduced since then.

Why feed colonies?

All colonies need sufficient stores to get the colony through the winter until suitable nectar sources and good enough weather make foraging profitable the following spring.

How much the colony needs depends upon the bees themselves – some strains are more frugal than others – and the duration of the winter. If there is no forage available, or the weather is too poor for the bees to fly, then they will be dependent upon stores in the hive.

A reasonable estimate would probably be somewhere around 20 kg of stores, but this isn’t a precise science.

It’s better for the colony to have too much than too little. 

If the colony has stores left over at winter’s end you can always remove them and use them when you make up nucs later in the season. Just pull out the frames and store them safely until needed.

Unused winter stores

In contrast, if the colony starts the winter with too few stores there are only two possible outcomes:

  • the colony will starve to death, usually in late winter/early spring (see below)
  • you will spend your winter having to regularly check the colony weight and opening the hive to add “emergency rations” to get them through the winter

Neither of these is desirable, though you should expect to have to check the colony periodically in winter anyway.

Feeding honey for the winter … and meaningless anecdotes

By the end of the summer the queen has reduced her laying rate and the bees should be backfilling brood comb with honey stores. If you assume there’s about 5 kg of stores 2 in the brood box then they’ll need about another 15 kg. 

15 kg is about the amount of honey you can extract from a well-filled super. 

Convenient 😉

Some beekeepers leave a full super of honey on the hive, claiming the “it’s better for the bees than syrup”

Of course, it’s a free world, but there are two things wrong with doing this:

  • where is the evidence that demonstrates that honey is better than sugar-based stores?
  • it’s an eye-wateringly expensive way to feed your colonies

By evidence, I mean statistically-valid studies that show improved overwintering on honey rather than sugar.

Not ‘my hive with a honey super was strong in spring but I heard that Fred lost his colony that was fed syrup’ 3.

That’s not evidence, that’s anecdote.

If you want to get this sort of evidence you’d need to start with a lot of hives, all headed by queens of a similar age and provenance, all with balanced numbers of brood frames/strength, all with similar mite levels and other pathogens.

For starters I’d suggest 200 hives; feed 50% with honey, 50% with sugar … and then repeat the study for the two following winters.

Then do the stats 4.

The economics of feeding honey

If I were a rich man …

The 300 supers of honey used for that experiment would contain honey valued at about £80,000.

That’s profit, not sale price (though it doesn’t include labour costs as I – and many amateur beekeepers – work for free).

The honey in a single full super has a value of £250-275 … that’s an expensive way to feed your bees 5.

Particularly when it’s not demonstrably better than a tenner or so of granulated sugar 🙁

But there are more costs to consider

The economic arguments made above are simplistic in the extreme. However, there are other costs to consider when feeding colonies.

  • time taken to prepare and store whatever you will be feeding them with 6
  • feeders needed to dispense the food (and storage of these when not in use)
  • energetic costs for the colony in converting the food to stores

Years ago I stopped worrying (or even thinking much) about any of this and settled on feeding colonies fondant in the autumn.

Fondant mountain ...

Fondant mountain …

Fondant is ~78% sugar, so a 12.5 kg block contains about 9.75 kg of sugar.

This year I’m paying £11.75 for fondant which equates to ~£1.20 / kg for the sugar it contains.

In contrast, granulated sugar is currently about £0.63 / kg at Tesco.

The benefits of fondant

Although my sugar costs are about double this is a relatively small price I’m (more than) prepared to accept when you take into account the additional benefits.

  • zero preparation time and no container costs. Fondant comes ready-wrapped and stores for years in the box it is purchased in
  • no need for jerry cans, plastic buckets or anything to prepare or store it in before use
  • no need for expensive Ashforth-type feeders that sit around for 95% of the year unused When I last checked an Ashforth feeder cost £66 😯 
  • it takes less than 2 minutes to add fondant to a colony
  • no risk of spillages – in the kitchen, the car or the apiary 7.
  • fondant is taken down more slowly than syrup, so providing more space for the queen to continue laying. In addition, in the event of an early cold snap, fondant remains accessible whereas bees often stop taking syrup down

Regarding the energetic costs for the colony in storing fondant rather than syrup … I assume this is the case based upon the similarity of the water content of fondant to capped stores (22% vs. 18%), whereas syrup contains much more water and so needs to be ripened before capping to avoid fermentation.

Fondant block under inverted perspex crownboard – insulation to be added on top.

Whether this is correct or not 8, the colony has no problem taking down the fondant over a 2-4 week period and storing it.

What are the disadvantages of using fondant? 

The only one I’m really aware of is that the colony will not draw fresh comb when feeding on fondant (or at least, not enthusiastically). In contrast, bees fed syrup in the autumn and provided with fresh foundation will draw lovely worker brood comb. 

Do not underestimate this benefit.

They fancied that fondant

Brood frames of drawn comb are a very valuable resource. Every time you make up a nuc, or shift a nuc to a full-sized box, providing drawn comb significantly speeds up the expansion of the resulting colony.

Nevertheless, for me, the advantages of fondant far outweigh the disadvantages …

Finally, in closing, I’ve not purchased or used invert syrup for feeding colonies. Other than no prep time this has the same drawbacks as syrup made from granulated sugar. Having learnt to use fondant a decade or so ago from Peter Edwards (Stratford BKA) I’ve never felt the need to look at other options.

Let’s move on …

Ventilation and insulation

Bees can withstand very cold temperatures if healthy and provided with sufficient stores. In northern Canada bees may experience only 120 frost-free days a year, and cope with 3-4 week periods in winter when the temperature is -25°C (and colder if you consider the wind chill).

That makes anywhere in the UK look positively balmy.

Margate vs. the Maldives … a similar temperature difference to Margate vs. Manitoba in the winter

I’ve overwintered colonies in cedar or poly boxes for a decade and not noticed a difference in survival rates. Like the honey vs. sugar argument above, if there is a difference it is probably minor. 

However, colony expansion in poly boxes in the spring is usually better in my experience, and they often fill the outer frames with brood well before cedar boxes in the same apiary get there.

Whether cedar or poly I take care with three aspects of their insulation/ventilation:

  • the colonies have open mesh floors and the Varroa tray is only in place when I’m actively monitoring mite drop
  • all have insulation above the crownboard in the form of a 50 mm thick block of Kingspan (or Recticel, or Celotex), either integrated into the crownboard itself, placed above it or built into the roof
  • I ensure there is no upper ventilation – no matchsticks under the crownboard, no holes etc.
  • excess empty space in the brood box is reduced to minimise the dead air space the bees might lose heat to

In my experience bees actively dislike ventilation in the crownboard. They fill mesh with propolis …

Exhibit A … are you getting the message?

… and block up the holes in those over-engineered Abelo crownboards …

Exhibit B … ventilated hole in an Abelo crownboard

Take notice of what the bees are telling you … 😉

Insulation over the colony

I’ve described my insulated perspex crownboards before. They work well and – when inverted – can just about accomodate a flattened 9, halved block of fondant.

Perspex crownboard with integrated insulation

Finally, if it’s a small colony in a brood box 10 then I reduce the dead space in the brood box using a fat dummy

Fat dummy with integral feeder

Fat dummy …

I build these filled with polystyrene chips.

You don’t need this sort of high-tech solution … some polystyrene wrapped tightly in a thick plastic bag and sealed up with gaffer tape works just as well.

Insulation ...

Insulation …

I’ve even used bubblewrap or that air-filled plastic packaging to fill the space around a top up block of fondant in a super ‘eke’ before now.

However, remember that a small weak colony in autumn is unlikely to overwinter as well as a strong colony. Why is it weak? Would you be better uniting it before winter starts?

Nucleus colonies

Everything written above applies equally well to nucleus colonies.

A strong, healthy nuc should overwinter well and be ready in the spring for sale or promoting to a full colony.

Here's one I prepared earlier

Here’s one I prepared earlier … an overcrowded overwintered nuc in April

Although I have overwintered nucs in cedar boxes I now almost exclusively use polystyrene. This is another economic decision … a well made cedar nuc costs about double the price of the best poly nucs

I feed my nucs fondant in preparation for the winter, typically by adding 1-2 kg blocks to the integral feeder.

Everynuc fondant topup

Everynuc fondant topup

Because of the absence of storage space in the nuc brood box it’s not unusual to have to supplement this several times during the autumn and winter.

You can even overwinter queens in mini-mating nucs like Apidea’s and Kieler’s.

Kieler mini-nuc with overwintering queen

This deserves a post of its own. Briefly, the mini-nuc needs to be very strong and usually double- or triple- height. I build fondant frame feeders for Kieler’s that can be quickly swapped in/out to compensate for the limited amounts of stores present in the brood box.

Kieler mini-nuc frame feeders

My greatest success in overwintering these was in winters when I provided additional shelter by placing the nucs in an unheated greenhouse. A tunnel provided access to the outside. However, I know several beekeepers who overwinter them without this sort of additional protection (and have done so myself).

Just because this can be done doesn’t mean it’s the best thing to do.

I’d always prefer to overwinter a colony as a 5 frame nuc. The survival rates are much better, their resilience to long periods of adverse weather is significantly greater, and they are generally much more useful in the spring.

Miscellaneous musings

Hive weight

A colony starting the winter with ample stores can still starve if the bees are particularly extravagant, or if they rear lots of brood but cannot forage.

The rate at which stores are used is slow late in the year and speeds up once brood rearing starts again in earnest early the following spring (though actually in late winter).

Colony weight in early spring

As should be obvious, this is a Craptastic™ sketch simply to illustrate a point 😉

The inflection point might be mid-December or even early February.

The important message is that, once brood rearing starts, consumption of stores increases. Keep checking the colony weight overwinter and supplement with fondant as needed.

I’m going to return to overwinter colony weights sometime this winter as I’m dabbling with a weather station and set of hive scales … watch this space.

An empty super cuts down draughts

Periodically it’s suggested that an empty super under the (open mesh) floor of the hive ‘cuts down draughts’, and is therefore beneficial for the colony.

It might be.

But like the ‘overwintering on honey’ (and being a pedant scientist) I’d always want to see the evidence.

There are two claims being made here:

  • a super under the floor cuts down draughts
  • fewer draughts benefits the colony which consequently overwinters better


There are ways to measure draughts but has anyone ever done so? Remember, the key point is that the airflow around the winter cluster would be reduced if there are fewer draughts. 

Does a super reduce this airflow significantly over and above that already caused by the sidewalls of the floor?

And, even if it does, perhaps the colony ‘reshapes’ itself to accommodate the draught from an open mesh floor.

What shape is the winter cluster?

For example, in an uninsulated hive (including no insulation over the cluster) with a solid floor the cluster is likely to be roughly spherical. They minimise the surface area.

With an open mesh floor are they more ellipsoid, so avoiding draughts from below? If so, is this improved much by an empty super below the open mesh floor? Does the cluster change shape or position? I don’t know as I’ve not compared cluster shapes in solid vs. open mesh floors plus/minus a super underneath.

And anyway, an open mesh floor looks very like a baffle to me … how much better can it get? How draughty is it in the first place?

Is this example 8,639 for my ‘Beekeeping Myths’ book?

I do know that top insulation tends to flatten the cluster against the warm underside of the crownboard.

Midwinter cluster

A strong colony in midwinter

Having worked out that draughts are (or are not) reduced … you still need another couple of hundred hives to test whether overwintering success rates are improved!

More winter bees

Finally, always remember that the survival of the colony is dependent upon the winter bees. All other things being equal (stores, disease etc.), a colony with lots of winter bees will overwinter better than one with fewer.

This is one of the reasons I stopped using Apiguard for mite control in autumn. Apiguard contains thymol and quite regularly (30-50% of the time in my experience) stopped the queen from laying, particularly in warmer weather. 

Apiguard works well for mite control, but I became wary that I was potentially stopping the queen at a time critical for late-season colony development. I worried that, once treatment was finished, a cold snap would shut down brood rearing leaving it with suboptimal numbers of winter bees.

I never checked to see whether the queen ‘made good’ any shortfall after removal of the treatment … instead I moved to Scotland where it’s too cold to use Apiguard effectively 🙁


Cut your losses

The stats for winter losses in the UK, Europe and USA can make for rather sobering reading.

In the UK, losses over the last 12 years have fluctuated between 9% and 34%. This self-selecting survey includes responses from about 10% of the British Beekeepers Association membership (primarily England and Wales, despite the name). The average number of hives maintained by a BBKA member is about 5, meaning – all other things being equal 1 – that most beekeepers should expect to lose about 1 hive every winter.

BBKA winter losses survey

About 30 countries, mainly Northern hemisphere, contribute to the COLOSS survey which is significantly larger scale. The most recent 2 data published (for the ’16/’17 winter) had data from ~15,000 respondents 3 managing over 400,000 hives. Of these, ~21% were lost for a variety of reasons. COLOSS data is presented as an unwieldy table, rather than graphically. Further details, including recently published results, are linked from their website.

In the USA the Bee Informed Partnership surveys losses – both winter and summer – and claims to have results that cover ~10% of all the colonies in the country (so probably between 250,000 and 275,000 hives). Winter losses in the USA are rarely reported at less than 20% and were as high as 35% in the ’18/’19 winter 4.

Bee Informed Partnership annual colony losses

Are these figures to be trusted?

Who knows?

Each survey is accompanied by a variety of statistics. However, since they all appear to be based upon voluntary reporting by a subset of beekeepers, there are opportunities for all sorts of data to be included (and even more to be missed entirely). 

The problem with surveys

Is the successful beekeeper who managed to get all her colonies through the winter more likely to respond?

A form of ‘bragging rights’.

What about the beekeeper that lost all his colonies?

Does he respond out of a sense of responsibility?

Or does he keep quiet because he doesn’t want to be reminded of those cold, quiet, mouldy boxes opened on the first warm day of spring?

One and two year beekeepers

What about the high level of annual ‘churn’ amongst beekeepers? They buy a nuc in May, filled with enthusiasm about the jars of golden honey they’ll have for family and friends in late summer.

To say nothing of all the “saving the bees” they’ll be doing.

But by late summer the colony is queenless and has an unpleasant temperament

Beekeeping should be enjoyable ...

Beekeeping should be enjoyable …

Psychopathic you might say … if you were feeling uncharitable.

Consequently the Varroa treatment goes on far too late,. Or is quietly forgotten. The winter bees have high viral loads and ‘die like flies’ 5, resulting in the colony succumbing by the year end.

But this colony loss is never recorded on any surveys.

The once enthusiastic beekeeper has moved on and is now passionate about growing prize-winning vegetables or cheesemaking or keeping chickens. 

Beekeeping associations train lots of new beekeepers and – although membership numbers are increasing – it’s well below the rate they’re trained at.

Some may not be ‘joiners’ and go their own way.

Many just quietly stop after a year or two.

How many people have you met that say “Oh yes, I used to keep bees”

Did you ask them whether they ever completed a winter losses survey?

I’m not sure any of the surveys listed above do much ‘groundtruthing’ to establish whether the data they collect is truly representative of the population actually surveyed. With large numbers of respondents spread across a wide geographic and climatic range it’s not an easy thing to do.

So, treat these surveys with a healthy degree of scepticism.

Undoubtedly there are high levels of winter losses – at least sometimes – and the overall level of losses varies from year to year.

Losses and costs

The direct financial cost of these colony losses to beekeepers is very high.

Ignoring time invested and ‘consumables’ like food, miticides and foundation these costs in ’16/’17 for just Austria, the Czech Republic and Macedonia were estimated at €56 million 😯  

These figures simply reflect lost honey production and the value of the lost colonies. They do not include the indirect costs resulting from lost pollination.

But, for the small scale beekeeper, these economic losses are irrelevant.

Most of these beekeepers do not rely on bees for their income.

The real cost is emotional 🙁

It still saddens me when I lose a colony, particularly when I think that the loss was avoidable or due to my incompetence, carelessness or stupidity 6.

Little snow, big snow. Big snow, little snow.

Your hives should be quiet in winter, but it hurts when they are silent in spring.

Anatomy of a death

The COLOSS surveys give a breakdown of winter losses in three categories:

  • natural disasters
  • queen problems
  • dead colonies

Natural disasters are things like bears, honey badgers, flooding or falling trees.

We can probably safely ignore honey badgers in the UK, but climate change is increasing the weather extremes that causes flooding and falling trees.

Moving to higher ground ...

Moving to higher ground …

Don’t assume that poly hives are the answer to potential flooding.

They do float, though not necessarily the right way up 🙁

Queen problems cover a variety of issues ranging from reduced fecundity to poor mating (and consequent drone laying) to very early or late – and failed – supersedure 7.

Beekeepers with a lot more experience than me report that queen problems are increasing.

Drone laying queen ...

Drone laying queen …

Perhaps the issues with fecundity and drone laying are related to toxic levels of miticides in commercial foundation? It’s certainly known that these residues reduce drone sperm fertility significantly. I intend to return to this topic sometime during the approaching winter … perhaps in time to encourage the use of some foundationless frames for (fertile) drone production 😉

In the ’16/’17 COLOSS data, natural disasters accounted for 1.6% of all overwintered colonies (so ~7.5% of losses), queen problems resulted in the loss of 5.1% of colonies (i.e. ~24% of losses) and the remainder (14.1% of colonies, ~68% of losses) just died.

Just died?

We’ll return to natural disasters (but not bears or honey badgers) and queen problems shortly. What about the majority of losses in which the colony ‘just died’?

If you discuss colony post-mortems with beekeepers they sometimes divide the ‘just died’ category (i.e. those not readily attributable to failed queens, marauding grizzlies or tsunamis) into four groups:

  • disease
  • isolation starvation
  • starvation
  • don’t know 

The most important disease associated with overwintering colony losses is high levels of Deformed wing virus (DWV). This results from uncontrolled or inadequately controlled Varroa infestation. For any new readers of this site, please refer back to many of the articles I’ve already written on Varroa management 8.

I strongly suspect that a significant proportion of the reported isolation starvation is actually also due to disease, rather than isolation per se.

A consequence of high levels of DWV is that winter bees die prematurely. Consequently, the colony shrinks faster than it would otherwise do. It starts the size of a basketball but (too) rapidly ends up the size of a grapefruit … or an orange.

Isolation starvation and disease

The small cluster is then unable to remain in contact with stores, and so starves. 

Yes, the colony died from ‘isolation starvation’, but the cause was the high levels of Varroa and the viruses it transmits.

Isolation starvation ...

Isolation starvation …

What about regular starvation?

Not because the cluster became isolated from the stores, but simply because they had insufficient stores to get through the winter.

Whose fault was that?

And the last category, the “don’t knows”?

I bet most of these are due to high levels of Varroa and DWV as well 🙁

Yes, there will be other reasons … but probably not a huge number. 

What’s more … if you don’t know the reason for the colony loss there’s very little you can do to mitigate against it in future seasons.

And, other than wild and increasingly vague speculation, there’s little I can write about if the reason for the loss remains unknown 9.

Avoiding winter losses

So, let’s rationalise those earlier lists into the probable (known) major causes of overwintering colony losses:

  • natural disasters
  • queen problems
  • starvation
  • disease (but probably mainly DWV and Varroa

As the long, hot days of summer gradually shorten and cool as early autumn approaches, you should be thinking about each of these potential causes of overwintering colony loss … and doing what you can to ensure it doesn’t happen to you (or, more correctly, your bees).

Ardnamurchan autumn

Ardnamurchan autumn

Some are easier to deal with than others.

Here’s a whistle-stop tour of some more specific problems and some practical solutions 10. Some, all or none may apply to your bees – it depends upon your location, your climate, your experience and future plans as a beekeeper. 

Natural disasters

These fall into two broad groups:

  • things you can do almost nothing about (but might be able to avoid)
  • things you can relatively easily solve

Flooding, falling trees, lightning, landslides, earthquakes, volcanoes, meteor strikes etc. all fall into the first group.

If you can avoid them, do. 

Your local council will have information on areas at risk from flooding. There are also searchable maps available from SEPA. Do not underestimate the severity of some of the recent flooding. Some parts of Scotland and Northern England had 600 mm of rain in two days in 2015.

You might be surprised (and from an insurance aspect, devastated) at the classification of some areas now ‘at risk’. 

Where did Noah keep his bees? In his Ark hive.

Where did Noah keep his bees? In his Ark hive.

Consider moving hives to higher ground before the winter rains start. One consequence of climate change is that heavy rainfall is now ~20% heavier than it was a few decades ago. This means that floods occur more frequently, are more extensive and the water levels rise faster. You might not have a chance to move the hives if flooding does occur,

More rain and stronger winds (particularly before leaf fall) mean more trees will come down. You might be able to identify trees potentially at risk from falling. It makes sense to remove them (or site your hives elsewhere). 

No risk of this larch tree falling on my hives

Lightning, earthquakes, volcanoes, meteor strikes … all a possibility though I would 11 probably worry about Varroa and woodpeckers first 😉

Solvable natural disasters

The ‘solvable’ natural disasters include preventing your colonies being robbed by other bees or wasps. Or ransacked by mice or woodpeckers after the first hard frosts start. A solution to many of these are ‘reduced size entrances’ which either enable the colony to better defend itself, or physically restricts access to critters.

The L-shaped ‘kewl floors‘ I use prevent mice from accessing the brood box. They are also easier for the colony to defend from bees/wasps, but can also easily be reduced in size with a narrow piece of hardwood. If you don’t use these types of floor you should probably use a mouseguard.

Polyhives and polythene

Polyhives and polythene …

Woodpeckers 12 need to cling onto the outside of the hive to hammer their way through the side. You can either place a wire mesh cage around the hive, or wrap the box in something like damp proof membrane (or polythene) to prevent them gaining purchase on the side walls.

Keep off Woody

Keep off Woody

Doing both is probably overkill though 😉

Strong colonies

Before we move onto queen problems – though it is related – it’s worth emphasising that an even better solution to prevent robbing by bees or wasps is to maintain really strong colonies.

Strong colonies with a well balanced population of bees can almost always defend themselves successfully against wasps and robbing bees.

Nucs, that are both weaker and – at least shortly after being made up – unbalanced, are far less able to defend themselves and need some sort of access restriction.

By ‘balanced’ I mean that the numbers and proportions of bees fulfilling the various roles in the nucleus colony are reflective of a full hive e.g. nurse bees, foragers, guard bees. 

Reduced entrance ...

Reduced entrance …

But the benefits of strong colonies are far greater than just being able to prevent wasps or robbing bees. There is compelling scientific evidence that strong colonies overwinter better

I don’t mean strong summer colonies, I mean colonies that are strong in the late autumn when they are fully populated with the winter bees.

Almost the entire complement of bees in the hive are replaced between late summer and late autumn. Remember that a really strong summer colony may not be strong in the winter if Varroa and virus levels have not been controlled.

How do you ensure your colonies are strong?

  1. Minimise disease by controlling Varroa levels in early autumn to guarantee the all-important winter bees are reared without being exposed to high levels of DWV.
  2. Try and use a miticide treatment that does not reduce the laying rate of the queen.
  3. Avoid blocking the brood nest with stores where the queen should be laying eggs.
  4. Requeen your colonies regularly. Young queens lay more eggs later into the autumn. As a consequence the colonies have increased populations of winter bees.
  5. Unite weak colonies (assuming they are disease-free) with stronger colonies. The former may well not survive anyway, and the latter will have a better chance of surviving if it is even stronger – see below. 
  6. Use local bees. There’s good evidence that local bees (i.e. reared locally, not imported from elsewhere) overwinter better, not least because they produce stronger colonies.

Uniting – take your losses in the autumn

My regular colony inspections every 7-10 days during May and June are pretty much abandoned by July. The risk of swarming is very much reduced after the ‘June gap’ in my experience. 

I still check the colonies periodically and I’m usually still rearing queens. However, the rigour with which I check for queen cells is much reduced. By July my colonies are usually committed to single-mindedly filling the supers with summer nectar.

They are already making their own preparations for the long winter ahead.

Although the inspections are less rigorous, I do keep a careful watch on the strength of each colony. Often this is directly related to the number of supers I’ve had to pile on top.

Colonies that are underperforming, and – more specifically – understrength are almost always united with a stronger colony.

An Abelo/Swienty hybrid hive ...

An Abelo/Swienty hybrid hive …

Experience has taught me that an understrength colony is usually more trouble than it’s worth. If it’s disease-free it may well overwinter reasonably well. However, it’s likely to start brood rearing more slowly and build up less well. It may also need more mollycoddling 13 in the autumn e.g. protection from wasps or robbing bees.

However, a colony that is not flourishing in the summer is much more likely to struggle and fail during the winter. Perhaps the queen is not quite ‘firing on all cylinders’ and laying at a really good rate, or she might be poorly mated.

Far better that the workforce contributes to strengthening another hive, rather than collect an underwhelming amount of honey before entering the winter and eventually becoming a statistic.

My winter losses are low and, over the last decade, reducing.

That’s partly because my Varroa management is reasonably thorough.

However, it’s probably mainly due to ensuring only strong colonies go into the winter in the first place.


I’ve dealt with uniting in several previous posts.

It’s a two minute job. 

You remove the queen from the weak colony, stack one brood box over the other separated by a sheet or two of newspaper with a very small (~3mm) hole in the middle. Add the roof and leave them to get on with things.

I don’t think it makes any difference whether the strong colony goes on the top or the bottom.

I place the colony I’m moving above the box I’m uniting it with. My – wildly unscientific – rationale being that the bees in the top box will have to negotiate the route to the hive entrance and, in doing so, will help them orientate to the new location faster 14.

If you unite colonies early or late in the day most foragers will be ‘at home’ so not too many bees will return to find their hive missing.

If there are supers on one or both hives you can separate them with newspaper as well. Alternatively, use a clearer the day before to empty the supers prior to uniting the colonies. You can then add back the supers you want and redistribute the remainder to other hives in the apiary.

Successful uniting ...

Successful uniting …

Don’t be in too much of a hurry to check for successful uniting.

Leave them a week. The last thing you want is for the queen to get killed in an unseemly melee caused by you disturbing them before they have properly settled.

Done properly, uniting is almost foolproof. I reckon over 95% of colonies I unite are successful.

That’s all folks … more on ‘Cutting your losses’ next week 🙂


At just over 3000 words this post got a bit out of control … I’ll deal with more significant queen problems, feeding colonies, the weather and some miscellaneous ‘odds and sods’ next week.

Irrational Varroa control

About a month ago I wrote a post on rational Varroa control. I define this as choosing a miticide appropriate for your colony 1 and environment, administering it properly and at the right time so providing the maximum benefit to your bees. The long term goal of rational Varroa control is reduced colony losses due to mite-transmitted viruses.

Primarily this means reduced overwintering losses due to Deformed wing virus.

I regularly give talks on this topic. In these I provide a few brief examples of the misuse of miticides. Some of these examples originate – anonymised – in questions I’ve received in previous talks or by email. Some are from surveys of miticide usage.

Winter is coming – miticide treatments and fondant on

A few (a very few) are from direct personal experience 🙁

I’m aware that these examples qualify as ‘misuse’ because I’ve read up about the active ingredient in miticides and have a reasonable understanding of how, when and why they work.

Misuse could probably be broken down into three divisions:

  • Incorrect usage that does not reduce the efficacy of the treatment. 
  • Using the miticide in a manner that significantly reduces its efficacy, but otherwise does little or no harm.
  • Incorrect usage that has no impact upon the mite population and/or that significantly harms the colony and/or spoils the honey.

After a short 2 preamble, I’ll outline some of the more glaring examples. Keep these in mind when planning your mite control strategy and you should see improved winter survival, better spring build up, stronger summer colonies … and more honey 🙂

What can I use?

The Veterinary Medicines Directorate maintain a list of miticides approved for use on honey bees (and other animals). It’s a large database and I find the easiest way to see the current product list – which changes quite regularly as things are added and removed – is to use the search facility.

VMD database search … bees, budgies and bearded dragons

Simply select ‘Bees’ from species list (they’re between ‘Bearded dragons’ and ‘Budgies’!) and then hit the big Run search button at the bottom.

There are currently 31 approved products though this contains a number of duplicates as Great Britain and Northern Ireland are listed as separate territories.

In my view, the two most important useful columns in the returned table are the ‘Active substance‘ and the ‘Aligned product‘. 

The active substance is the chemical in the miticide that is responsible for killing mites. 

Look down the list. There are relatively few different active substances, present alone or in combination.

I currently count just five.

And then there were five … VMD approved miticides classified by active ingredient

Thymol, amitraz, pyrethroids, formic acid and oxalic acid.

I’m ignoring the minor components like eucalyptus oil that, individually, do not have high levels of miticidal activity.

Flumethrin and tau-fluvalinate (the active ingredients of Bayvarol and Apistan respectively) are both pyrethroids and have the same mode of action (and, more importantly, resistance to one usually confers resistance to the other).

What about management methods to control mites?

The VMD database lists the miticidal products approved for treating honey bees. 

They don’t list management techniques like drone brood uncapping or small cell foundation, or the application of non-toxic compounds like dusting with icing sugar.

There’s nothing to stop you using these approaches.

However, first conduct some sort of cost-benefit analysis to determine if they are worthwhile.

Is the disruption to the colony, or the potential tainting of honey stores, justified by the reduction of Varroa numbers?

For example, Randy Oliver has done some analysis of the impact of sugar dusting and shows that – at best and with weekly applications – it might be able to hold Varroa levels steady. You can download his Excel calculations and play with some of the assumptions.

If you increase the percentage of mites capped in cells from 60% (which is probably rather conservative) and decrease the percentage of mites dislodged by sugar dusting from 40% (which is probably rather aggressive) then mite replication rapidly outruns the control method applied.

That’s a questionable ‘benefit’ in return for the disruption of blowing 120 g of icing sugar into the hive every 7 days 3 … but there’s nothing to stop you using it as a control method.

Though it might not do much controlling … 🙁

I choose miticides that kill at least 90% of mites when used properly. I prefer to use miticides once or twice during the season, rather than dabbling every other week or month.

What can’t or shouldn’t I use?

You cannot use things like fenpyroximate, spirotetramat or spirodiclofen.


These are used for mite or tick treatment of other animals or plants 4. They have been shown to be effective against Varroa (though at high levels they may also kill bees) but are not approved for use. 

Remember also that VMD approval involves both the compound and the mode by which it is administered.

Amitraz is approved for use as the active ingredient in Apivar strips. However, in Great Britain and Northern Ireland you cannot fumigate colonies with amitraz … which, as Apiwarol, is a popular treatment method in Poland.

There are some (perhaps surprising) ‘restrictions’ in terms of approved usage. Api-Bioxal can be used to trickle treat twice per season, but only used once for vaporisation.


This is one of the many oddities buried in the depths of the VMD database.

Api-Bioxal is not approved for spray administration, but Oxuvar is. Both have the same active ingredient. 

No wonder beekeepers find this confusing … 🙁

Read the instructions and other documentation

Miticides approved by the VMD come with documentation. This takes the form of the instructions written (often in really tiny print) on the packet. The other thing written on the packet is the ‘use by’ date. 

Apivar instructions – duration of treatment

Keep the packaging 🙂

Read the instructions for use.

It may seem like an obvious thing to suggest but at least a third of the questions I get asked are answered in the documentation.

Part of the problem is the wording that’s often used or the apparent (and sometimes real) contradictions between the instructions provided for two miticides that have the same active ingredient and formulation 5

Api-Bioxal additional documentation

For more legible documentation you could refer again to the VMD database of approved miticides. If you following the Aligned product’ link you will have access to several additional pieces of information, most useful of which are the Summary of product characteristics and the Product literature. The latter is a copy of the literature in a very easy-to-read format, without any fancy colours or tiny fonts.

Keep records

You should keep records of when you treat and what you treat with, including batch numbers. I simply keep the packet the miticide was supplied in. I know when I treated as my copious 6 notes record the dates … and allow me to work out when the period of treatment is finished.

Apivar (but the batch number is on the back of the packet)

Even easier … just take a photograph of the empty packet, but make sure you include the batch number in the shot.

Examples of miticide misuse

It’s not possible to provide a comprehensive set of examples of miticide misuse (or Irrational Varroa control) … at least not in ~2000 words 😉 – after all, there might be one or two ways to use a miticide properly, but thousands of ways it could be used improperly.

Here is a non-exclusive and far-from-comprehensive list of miticide misuse or bad practice. 

Don’t do this at home … or in the out apiary 😉

Too little

Use the correct dose. Using less than the recommended dose ensures that some mites will survive. This may lead to the development of mite resistance.

Some beekeepers have been known to add a single strip of Apivar to colonies in preparation for going to the heather moors.

This is bad practice.

Even worse … some have been found leaving the strip in the hive while they were at the heather. Is that forgetfulness or just reckless? The honey will be tainted  and the long-term exposure to low levels of amitraz may contribute to the development of resistance 7.

Too late

Remember that the goal of the late summer treatment is to prevent the developing winter bees from being exposed to Varroa and the viruses that the mite transmits.

If you treat too late in the season you may well kill lots of mites, but the winter bees will already have been exposed.

Mite levels (solid lines) when treated July to November and timing of winter bee production.

In the graph above, treating in mid-October will kill significantly more mites than treating in mid-August.

But that’s not really the goal.

An October treatment will kill more mites because they’ve been breeding like rabbits throughout September.

And, what have they been reproducing on? Your developing winter bee pupae 🙁

Winter bee production is not an all or nothing event. The colony does not switch from producing summer bees to winter bees on a particular date. As late summer segues into early autumn an increasing proportion of the developing brood will be winter bees.

It’s your responsibility to ensure that enough of them are protected from Varroa so that they can lead a long and protective life, getting the colony through until February or March next year.

Too much

Many miticides are reasonably well tolerated by bees. Nevertheless, overdosing is also to be avoided. If you read the product characteristics for Api-Bioxal for example it states that:

Significantly higher bee mortality was observed in hives that received double (by sublimation) or triple (by trickling) dosages of product. In addition, when overdosed, the over-wintering  capacity of colonies was diminished and there may be detrimental effects on colony development in the future 8.

Remember that nucleus colonies are smaller than full sized colonies. It’s not unusual for a  beekeeper to administer a full dose to what is essentially a half-sized colony. 

In the case of Amitraz, ‘overdosing’ is well tolerated and two strips in a nucleus colony is unlikely to do the bees any harm.

However, the same cannot be said of MAQS. The product characteristics for MAQS specifically state that it should not be used for colonies with less than 6 frames of brood.

Too high

The formic acid-containing MAQS is poorly tolerated by the colony at high ambient temperatures. The literature suggests it should not be used when the peak daily temperature might exceed 29.5°C.

I’ve never used MAQS. I’m told by other beekeepers that they’ve had problems with queen losses at temperatures as ‘low’ as 25°C.

Remember, when you add the MAQS strips they need to be in the hive for 7 days. You therefore need to check the forecast for the week ahead before starting treatment.

Too low

Alison Gray and Magnus Peterson (both at Strathclyde University) have conducted surveys of Scottish beekeepers for about the last 15 years, summaries of which appear annually in The Scottish Beekeeper. Results are also collated into the COLOSS analysis. 

The surveys have evolved over the years, but have included questions on the type and timing of treatment.

I read some of these carefully when I returned to live in Scotland (in 2015). I was interested to see what other beekeepers were using. One thing that surprised me was the amount and timing of thymol (Apiguard) treatment.

For example, in the 2014 report (PDF), ~25% of treatments used were thymol, with 60% of these being applied in September, October and November.

A quick check of the Apiguard Product characteristics turns up the following statement:

Do not use the product when the maximum daily temperature expected during the treatment is lower than 15°C or when the colony activity is very low or when temperature is above 40°C.

I don’t know anywhere in Scotland in where the maximum daily temperature exceeds 15°C for four weeks (the duration of treatment) between September and November. 

I checked a personal weather station a couple of miles from my apiaries in Fife … in October 2013 the average temperature was 11.5°C, but the maximum failed to reach 15°C on 10 days through the month.

Inevitably, the efficacy of treatment would be reduced.

West coast temperatures 26/7/21 to 26/8/21 … 7 days fail to reach 15°C making Apiguard a very poor choice here.

You need good long range weather forecasting skills. Prior experience of what might be expected can really help your planning in these circumstances. 

Too long

Do not leave Apivar strips in the colony longer than stated in the instructions. 

How long is that?

Again, from the Product characteristics documentation:

If brood is not present or at its lowest level, the strips can be removed after 6 weeks of treatment. If brood is present, leave the strips in place for 10 weeks and remove the strips at the end of treatment.

Strips added to a colony with a young queen (and therefore laying well, and late into the year) on the day this article appears 9 should probably be removed in the first week of November.

Used and removed Apivar strips

That’s not a great time of year to be lifting roofs and prising up crownboards.

However, the alternative is worse. If you leave the strips in situ you ensure that any surviving mites (and there will be some) are continuously exposed to a low level of amitraz … perfect conditions to help select for resistance 🙁

Too short

This is much the same as too little (see above). If you remove the miticide before the correct period of time has elapsed then some mites will escape treatment.

No miticide is 100% effective. However, why store up problems for the future by unnecessarily reducing the efficacy of the treatment?

Remember … the only good mite is a dead mite

Too old

Miticides are not inexpensive. It is therefore very tempting to save and re-use opened packets. 

For example, beekeepers with just a couple of hives still have to purchase a packet of Apivar 10 for an eye-watering £31. It must be very tempting to tuck the unused portion away in the shed for the next time.

And, when they do, how many do a before and after count of phoretic mites to confirm that the treatment worked?

I suspect very few. 

If they did they might be in for a bit of a disappointment.

Amitraz, the active ingredient in Apivar strips, is quite unstable and rapidly degrades. I’ve used strips from previously opened packets and observed that they were significantly less effective 11.

What I should have done was read the Product characteristics documentation where it clearly states:

Shelf life after first opening the immediate packaging: use immediately and discard
any unused product.

Similar problems (short or non-existent shelf life) apply to some of the oxalic acid-containing solutions, in this case because they degrade to product hydroxymethylfurfural which is toxic to bees at high concentrations (see the notes on this at the end of the post of preparing Api-Bioxal for trickle treating).

One and two hive owners should coordinate their purchases and treatment of colonies to avoid wasting money.

Coordinated treatment has additional benefits, which neatly takes me to the final topic … 

Too few

OK, these titles are getting a bit contrived now, but this is the last one 😉

Treat all the colonies in the apiary simultaneously. I’ve written extensively about drifting and robbing. Both activities redistribute adult bees and the mites piggybacking on them around the apiary (or the wider environment).

If you treat just one colony it will soon 12 become reinfested with mites from neighbouring colonies.

If you don’t treat one colony and it develops high mite levels in autumn, perhaps due to a late surge in brood rearing, it will shed mites (hitching a ride on young bees going on orientation flights) to your adjacent treated colonies.

A final note on Apistan and pyrethroid-containing miticides

Resistance to Apistan is widespread. It’s so widespread that the National Bee Unit apparently stopped keeping records a decade or so ago.

Apistan is a very effective miticide … against mites that are sensitive. 

If you intend to use Apistan (or any of the approved pyrethroid-containing miticides) I would strongly suggest determining the level of infestation before treatment, and confirming a 90+% reduction in mite levels after treatment.

Unfortunately, just counting the dead mites on the Varroa tray is not evidence that the treatment has been effective.

If you find 1000 dead mites on the tray it just tells you is that you have 1000 mites less in the colony.

There may still be 9000 left if the treatment was only 10% effective … 

That’s not going to end well 🙁



One of the few principles I have ( 😉  ) is that the posts here should be based upon practical experience. When I write about swarm control I describe the methods that I use. When I write about Varroa management I discuss Apivar and oxalic acid in detail as I have a lot of experience using these compounds. I’ve not written about MAQS as I don’t use it.

For the same reasons, you won’t see a discussion about top bar hives or the Bee Guardian piezoelectric gadgets that causes the varroa mites stop to reproduce and go away from the hive” 1.

The topic today is absconding. My qualification to write about this is extremely limited, but just about sufficient. I think I’ve had only one colony abscond in the last decade. It’s not something I take any notice of (or precautions against) in my regular beekeeping. However, it’s an interesting subject as there’s some relevant science associated with absconding and honey bee migration, so it’s worth discussing.

And perhaps more science to do …

But first some definitions

Colony reproduction involves swarming. The colony rears one or more new queens. Once the queen cells are capped, the current queen and up to 75% of the adult bees leave the hive as a swarm. Prior to leaving, scout bees have scoured the environment for suitable new nest sites. These scouts lead the swarm to the chosen new location 2.

The swarm leaves behind all the brood and most of the stores. Together with the adult bees that remain, this colony has a good chance of survival (~80%) which is probably a reflection on queen mating success rates 3.

‘Most of the stores’ because the swarming bees gorge themselves on honey prior to leaving the hive (or nest site if it’s a feral colony). Something like 40% by weight of the swarm is honey stores. They need these stores to survive – to build new comb, to tide them over a period of bad weather and while they scout the environment for forage. Swarming is a risky business, only about 20% of natural swarms survive.

Absconding is very different. During this process the entire colony – the queen and all the flying bees – leave the nest site (hive). They usually leave behind almost nothing. There may be very limited amounts of capped brood/larvae or eggs remaining, but the stores are usually gone. Absconding therefore does not involve colony reproduction. There are no queen cells produced. You start with one colony and end with one.

However, although absconding is very different, it’s not completely different. It still involves scout bees and it still involves waggle dances to communicate distance and direction.

Like swarming, it’s also a completely natural process. In certain parts of the world there are annual cycles of absconding and colony migration.

In the discussion that follows I’m going to try and make a distinction between absconding by managed and unmanaged colonies. 

The consequences of either type of colony absconding are probably the same. 

The drivers that result in the colony absconding are sometimes different.

My experience

Let’s get this out of the way … 4

To my knowledge the only colony I have ever had abscond was from a Kieler mini-nuc. The mini-nuc had been primed with a mugful of bees and a queen cell a week or so earlier. The queen had emerged and may (or may not?) have gone on a mating flight 5.

An Apidea mini-nuc ‘catching a few rays’

One baking hot June afternoon I turned up at the apiary just as a small swirling mass of bees disappeared over the fence. 

Never to return 🙁

The mini-nuc was low on stores (but far from empty) and devoid of bees (or brood). There was drawn comb so the queen would have been able to lay (if she had been mated). I can’t remember whether there were eggs present … this was several years ago 6.

‘Natural’ absconding and colony migration

This mini-nuc wasn’t the one pictured, but it was similarly exposed. In full sun these can rapidly overheat and there is a real risk of the small colony absconding. I now always site my mini-nucs out of the heat of the full sun – even in Scotland – in dappled shade, at the bottom of a hedge or somewhere similar.

Of course, I don’t know that overheating caused this little colony to abscond, but it seems like a reasonable assumption.

Bees living in temperate and tropical regions exhibit gross behavioural differences that reflect the climate and availability of forage. Those in temperate climates swarm annually, coinciding with the predictable period of forage availability, and are quiescent over ‘winter’.

In contrast, bees in tropical climates have no ‘winter’ to survive as the temperature is high enough all year for brood rearing and comb building. What differs though is the availability of forage and water. If these are limiting the bees migrate to other areas.

This annual migration involves the colonies absconding … and it has been quite well studied by scientists.

Adverse environmental conditions are one of the recognised drivers of absconding. In addition to overheating, these include a dearth of resources during the wet season. 

The other major driver of absconding is disturbance, for example by predators such as ants (or beekeepers). Disturbance is a lot less predictable than environmental factors, and it is the latter that has been better studied.

Preparing to migrate

Absconding and migration appear to be a characteristic of strong, healthy colonies. Prior to absconding the colony reduces brood rearing drastically although the queen continues to lay a very limited number of eggs until the bulk of the worker brood has emerged 7.

Colonies tended to abscond within a day of this worker brood emerging, leaving almost nothing in the original nest site. 

So, this isn’t a spur of the moment decision, it’s a protracted process taking at least a fortnight from the near-cessation of brood rearing. This means the colony benefits from the resources they have invested in rearing brood, rather than leaving behind slabs of capped brood that would otherwise be doomed.

How does the colony know where to go when it absconds?

Actually, these preparations probably take more than a fortnight. Analysis of the waggle dances for several weeks prior to absconding show that the foraging area and distances were both increasing and becoming more variable. 

Schneider and McNally 8 showed that these waggle dances regularly communicated distances of up to 20 km from the nest site.

However, these weren’t typical dances … the distance component was variable, the dance occurred during periods of little flight activity and the dance was not associated with forage sources. They interpreted this as a generalised signal to fly for a long (but unspecified) distance in a particular direction, rather than to a specific location.

I’m not aware of follow-up studies to these. Do the bees go through the same sort of decision-making process to ‘agree’ on the final direction as the scout bees do when a colony swarms? I suspect not, the distance component was very variable and there was no direct evidence that the dancing bees ever made the entire journey anyway.

Perhaps these waggle dances simply indicate “Things are better a long way south of here. When we go, that’s the direction to take”.


If a colony absconds due to adverse environmental conditions – such as a lack of forage, or overheating – it seems unlikely that things would be much better only 20 km away. “environment” is local, but not necessarily that local.

In reality, colonies abscond and migrate much further than this when necessary, restoring in temporary stopover locations when necessary. In the case of Apis mellifera I’m not aware of any studies of these sites. However, in the Giant honey bee (Apis dorsata) some of these stopover locations appear to be re-used annually. 

Apis dorsata migrates up to 200 km and has even been reported crossing 50 km of open water between Sumatra and Malaysia. These long migrations take up to a month and the bees bivouac on trees, resting and replenishing their stores (by foraging locally) 9.

Giant honey bee (Apis dorsata) temporary stopover bivouac

Analysis of scout bee dancing activity on the surface of these bivouacked colonies show that this again determines the direction (and possibly distance) of the next stage of the journey. 

Absconding and managed colonies

I think it’s reasonable to assume that at least some of the factors that induce colonies to abscond in tropical regions also trigger absconding in our managed colonies in the UK. 

Very small colonies – like the mini-nuc described above – are poor at thermoregulation. There are simply too few bees present to cool the colony in very hot weather.

Although I’m aware that colonies may abscond due to disturbance – from wax moth, Varroa or small hive beetle infestation – I’ve no experience of this 10.

What about disturbance by beekeepers managing colonies? It’s a possibility I suppose. Clearly the regular weekly inspections are not sufficient disturbance to trigger absconding, but perhaps a daily rummage through the brood box might not be tolerated 11.

Absconding swarms

In temperate climates most beekeepers associate absconding with recently hives swarms.

Here’s a typical scenario …

The beekeeper is called out to a bivouacked swarm hanging – conveniently and precariously, just out of reach – in a tree.

By the time they’ve collected the ladder, the skep, the white sheet and the secateurs it’s late afternoon. Never mind … A swarm in May is worth a bale of hay etc.

A spring swarm in a skep

They drop the swarm into the skep, avoid toppling off the ladder, allow the flying bees to join the queen, wrap everything in the sheet and return triumphantly to their apiary 12.

In time honoured tradition they assemble a new hive, prop the entrance open and build a sheet-covered ramp onto which they unceremoniously dump the collected swarm.

'Walking' a swarm into a hive

‘Walking’ a swarm into a hive

And the bees calmly walk up the slope into the hive.

It’s one of the great sights in beekeeping … and one I now never bother to do.

I just dump the swarm into the hive and close it up. 

Boring, but quick 😉

Back to the absconding swarm scenario …

The beekeeper returns late the following morning to find the swarm has gone 🙁

Is this typical absconding?

Other than one or two typical circumstances such as a freshly painted (and still smelly) hive, I think that these swarms may abscond because they have already chosen an alternative nest site

The scout bees from the bivouacked colony (collected a day or two previously) had been busy surveying the environment for suitable nest sites. This process can take several days until a sufficient number of the scouts are convinced of the benefits of a particular site.

Once that decision is made the colony leaves the bivouac and flies to the new nest site. However, this flight tends to happen in the middle of the day, not late in the afternoon.

The beekeeper who hived our hypothetical swarm in the scenario above may have actually interrupted this process, which simply continued the following morning.

I don’t know if scout bees conduct waggle dances overnight to reinforce nest site choices (but the normal waggle dance for forage resources can occur during the night). If they do, this might account for the bees disappearing soon after being hived.

How do you stop hived swarms absconding?

There are three methods I’m aware of.

One is foolproof and I use every season. The other two are reported to work with variable levels of success, but which I have never used.

Adding a frame of open brood is reported to help stop the colony absconding. Alternatively, placing a queen excluder under the brood box (but above the floor) ‘traps’ the queen and prevents the colony leaving.

The first of these provides brood to care for, brood pheromones and the general ‘pong’ of a hive, all of which are likely to be beneficial. As I’ve not used this method I’m unsure how effective it is.

The queen excluder seems a heavy-handed and rather crude solution. The colony may well still try and abscond, but the queen will remain trapped. This seems like a great way to induce considerable stress in the colony.

And it’s unlikely to be successful long-term if the swarm is a cast with a virgin queen 😉

And the totally foolproof method?

Swarm arriving at bait hive ...

Swarm arriving at bait hive …

Bait hives.

I’ve never had a swarm that voluntarily arrived in a bait hive abscond. Even if I move the bait hive to another apiary, they still happily stay 🙂

Citizen science

I almost never hive bivouacked swarms these days as I am sufficiently successful in attracting swarms with bait hives 13.

I’m therefore unable to conduct the following experiment that I think would be quite interesting.

I’ve predicted above that a swarm collected from a bivouac that absconds may have already decided on the new nest site. By ‘hiving’ the swarm all the beekeeper is doing is moving the bivouac.

That being the case, I’d expect that collected swarms would be less likely to abscond if they’re moved to an area the scout bees have no knowledge of.

Scout bees survey the environment at least 3 km from the original nest site although swarms tend to occupy new nest sites well within this distance.

There are two things that would be interesting to monitor:

  1. Are swarms hived over 8 km from the location the swarm is collected less likely to abscond?
  2. Is the delay between hiving a swarm and it absconding related to the distance between the original bivouac and the initial location it is hived in?

I’ve chosen 8 km because you cannot always be certain where the bivouacked swarm came from (and because it’s a convenient 5 miles for these post-Brexit times). If you assume that the bivouac is always within a few dozen metres of the original nest site this ‘removal’ distance could be decreased to about 4 km.

The time delay addresses a slightly different question. I’m assuming here that the scout bees have yet to reach a quorum decision and are continuing to survey the environment. The further you move them, the more the environment changes, so potentially necessitating a longer decision making period.

As the 2021 season starts to wind down that’s something to think about for the year ahead.


Please don’t email me with all the gruesome details of swarms you’ve had abscond in the past. It’s not that I’m not interested … I’m just completely swamped with correspondence.

If there’s sufficient interest in this post over the next few months (and as a bit of ‘Citizen Science’ experiment which are all the rage) – determined by page accesses and comments – I’ll create a simple web form to log everything to a database. No individual beekeeper is likely to collect sufficient swarms to generate a meaningful amount of data. I doubt even if an entire association could do so. However, the thousands of readers a week are surely able to have enough hived swarms abscond to test the hypothesis?

Rational Varroa control

It’s the end of July … in the next two to three weeks the first eggs will be laid that will develop into the winter bees that get your colonies through to next spring. Protecting these winter bees is necessary to prevent overwintering colony losses.

I’ve written and lectured extensively on Varroa control and related topics for at least 5 years. The following article is published in August’s BBKA Newsletter and The Scottish Beekeeper. It provides an overview of what I term rational Varroa control.

I define this as effective mite management based upon our current understanding of the biology of bees and Varroa. The goal of this control is to minimise winter losses due to Varroa and viruses.

It is not a recipe with easy to follow if this, then that instructions. Neither does it provide a calendar-based guide of what to do and when to do it.

It does not even tell you what you should use for mite control.

Instead it focuses on the principles … understanding these will enable you to implement control strategies that help your bees, in your environment, survive.

This version is hyperlinked to additional, more expansive, posts on particular topics, is slightly better illustrated than those that appeared in print and contains some additional footnotes with caveats and exceptions.


Despite almost 30 years experience of Varroa in the UK, this ectoparasitic mite of honey bees remains the greatest threat to bees and beekeeping. With the exception of those fortunate to live in mite-free regions, all beekeepers must manage the mite population in their hives or risk losing the colony to the viruses transmitted when Varroa feeds on developing pupae. 

Fortunately, Varroa control is relatively straightforward; there are a range of approved and effective miticides that – used appropriately – reduce mite infestation levels significantly. The key words in that last sentence are ‘approved’, ‘effective’ and ‘used appropriately’. In reality annual colony losses, primarily occurring in the winter, often exceed 20% (Figure 1) and may be significantly higher in long or harsh winters 1. Many of these losses are attributable to Varroa and viruses. It is therefore clear that many beekeepers are not successful in managing Varroa; either they are not treating at all, or they are treating inappropriately.

Figure 1. BBKA winter survival survey – larger studies (COLOSS and BIP) often show much higher losses

This article is primarily aimed at relatively inexperienced beekeepers, but may also help the more experienced who still suffer with high levels of winter losses. It emphasises the importance of two, correctly timed, appropriate miticide treatments per season that should ensure colony survival. It is not going to deal with treatments of questionable or minor efficacy. These include the use of small cell foundation, drone brood culling or sugar dusting. These may reduce mite levels, but insufficiently to benefit colony health. Nor will it discuss the use of any miticides (or application methods) that are not approved by the Veterinary Medicines Directorate. I will also not discuss treatment-free beekeeping, selection of mite-resistant bees or advanced colony manipulations like queen trapping. In my view any or all of these could or should be tried … but only once a beekeeper can routinely successfully overwinter colonies using strategies similar to those described here.

The problem

Varroa is an ectoparasitic mite that feeds on developing honey bee pupae. During feeding it transmits a range of honey bee viruses, the most important of which is deformed wing virus (DWV). DWV is present in honey bees in the absence of Varroa. In our studies, using sensitive PCR-based detection methods, we never detect bees – even those from mite-free regions of Scotland – without DWV. The virus is transmitted horizontally between bees during trophallaxis, and vertically from drones or the queen through sperm or eggs. These routes of transmission are rarely if ever associated with any significant levels of disease and virus only replicates to modest levels (perhaps 1-10 thousand viruses per bee). However, when Varroa transmits DWV the virus bypasses the bee’s natural defence mechanisms and replicates to very high levels in recipient pupae (billions per pupa, 1 – 10 million times higher than in unparasitised pupae). Studies from our laboratory have shown that ~75% of pupae with these high virus loads either do not emerge, or emerge exhibiting the characteristic “deformed wings” that give the virus its name (Figure 2; Gusachenko et al., Viruses 2020, 12, 532; doi:10.3390/v12050532). The ~25% of bees that do emerge and appear ‘normal’ exhibit a range of symptoms including reduced fitness, impaired learning and reduced foraging. However, most importantly they also exhibit reduced longevity. During the summer this is probably not critical; the lifespan of a worker is only ~6 weeks and, assuming the queen is laying well, there are thousands of half-sisters around with more being produced every day.

DWV symptoms

Figure 2. DWV symptoms

But during the winter, brood rearing either stops completely or drops to a very low level. The bees reared from late summer onwards are physiologically very different. These are the ‘winter bees’, also termed the diutinus bees (from the Latin meaning long-lived). Physiologically these bees resemble juvenile workers and they can survive for many months. And they need to … it is these bees that get the colony through the autumn, winter and into the following spring. They protect the queen, they thermoregulate the hive and, usually around the winter solstice, they start to rear small amounts of new brood for the season ahead.

The longevity of the bees in the hive in winter is critical to colony survival. If the winter bees have high DWV levels their longevity is reduced (in addition to the reduced numbers due to overt disease or non-viability). This means that the winter cluster shrinks in size faster than it would do otherwise. With reduced numbers of bees it cannot keep brood warm enough and so the colony fails to expand early the following season. In cold spells it may be unable to reach the food stores resulting in the colony perishing from ‘isolation starvation’. It may not be able to maintain sufficient warmth to protect the queen, or may simply freeze to death.

The goal of rational Varroa control

Successful overwintering requires lots of winter bees. The size of the winter cluster is directly related to its survival chances. Therefore the goal of rational Varroa control is to prevent the winter bees from being exposed to mites and mite-transmitted viruses during their development. Winter bee production is induced by a range of factors including photoperiod, nectar and pollen availability, brood and forager pheromones. Together these induce slowed behavioural maturation of the winter bees. This is not like flicking a switch, instead it is a seamless transition occurring as late summer segues into early autumn (Figure 3). Winter bee production is also influenced by the queen. Young queens lay later into the autumn, so increasing the numbers of winter bees. 

Figure 3. Colony age structure from August to December.

It is important to note that these events are environment-driven, not calendar-driven. It will not happen at precisely the same time each year, or at the same time in different locations (or latitudes) each year.

To protect these winter bees the colony needs to be treated with an effective miticide before the majority of the winter bees are produced. This ensures that the developing winter bee pupae are not parasitised by virus-laden mites and so do not suffer from reduced longevity. 

When are winter bees produced in the UK? 

Unfortunately, I’m not aware of any direct studies of this. Scientists in Bern (49.9°N) in 2007/08, where the average temperatures in November and December were ~3°C, showed that the Varroa- and virus-reduced longevity of bees was first measurable in mid-November, 50 days after emergence. By extrapolation, the eggs must have been laid in the first week of September. 

Doing large scale experiments of Varroa control is time-consuming and subject to the vagaries of the climate (and, as a molecular virologist, beyond me in terms of the resources needed). I have therefore used the well-established BEEHAVE program of colony development (from scientists in the University of Exeter; to model the numbers of developing and adult bees, and the mite numbers in a colony. BEEHAVE by default uses environmental parameters (climate and forage) based upon data from Rothamsted (51.8°N). Using results from this model system, the bees present in the hive at the end of December – by definition the diutinus winter bees – were produced from eggs laid from early/mid August (Figure 4).

Whatever the precise date – and it will vary from season to season as indicated above – at some point in September the adult bee population starts to be entirely replaced with winter bees. Large numbers of these need to live until the following February or March to ensure the colony survives and is able to build up again once the queen starts laying.

When to treat – late summer

The numbers of pupae and adult bees present in the colony are plotted in Figure 4 using dashed lines. Adult bee number decrease in early spring until new brood is reared. The influence of the ‘June gap’ on pupal numbers is obvious. Brood rearing gradually tails off from early July and stops altogether sometime in late October or early November. The shaded area represents the period of winter bee production – from early/mid August until brood rearing stops. 

Figure 4. Winter bee production and mite levels – see key and text for further details

Mite levels are indicated using solid lines. The impact on the mite population of treating in the middle of each month from July to November is shown (arrowed and labelled J, A, S, O and N) using the colours green, blue, red, cyan and black respectively. The absolute numbers of bees or mites is irrelevant, but bees (pupae and adults) are plotted on the left, and mites on the right hand axis, so they cannot be directly compared. The miticide treatment modelled was ‘applied’ for one month and was 95% effective, reproducing many licensed and approved products.

Mite levels peak in the colony in late September to October. If treatment does not occur until this time of the season then the majority of winter bees will have been reared in the presence of large amounts of mites. Unsurprisingly, the earlier the treatment is applied, the lower the mite levels during the period of winter bee production. 

Rational Varroa control therefore involves treatment soon after the summer blossom honey is removed from the hive, so maximising the winter bees produced in the presence of low mite numbers. If you leave treatment until mid-September, you risk exposing the majority of winter bees to high levels of Varroa in the hive. If your primary crop is heather honey, which is not harvested until September, you may need to consider treating earlier in the summer – for example during the brood break when requeening or during swarm control.

Why treat in midwinter?

A key point to notice from Figure 4 is that, paradoxically, the earlier the miticide is applied, the higher the mite levels are at the end of the year. Compare the August (blue) and October (cyan) lines at year end for example. This is because mites that survive treatment – and some always do – subsequently reproduce in the small amount of brood reared late in the season. This is what necessitates a ‘midwinter’ treatment. Without it, mite levels increase inexorably year upon year, and cannot be controlled by a single late-summer treatment. Beekeepers bragging on social media that their mite drop after the winter treatment was zero probably applied the summer treatment too late to effectively protect their winter bees.

And when is midwinter?

Historically beekeepers apply the ‘midwinter’ treatment between Christmas and New Year. This is probably too late. The usual miticide used at this time is oxalic acid, a ‘one shot’ treatment that is ineffective against mites in capped cells. For maximum efficacy this must be applied when the colony is broodless. Brood rearing usually starts (if it ends at all, again this is climate-dependent) around the winter solstice. By delaying treatment until a lull in the Christmas festivities or even early January some mites will already be inaccessible in capped cells. 

Figure 5. Biscuit coloured (or a bit darker) cappings indicating brood rearing in this colony

I check my colonies for brood – either by looking for biscuit-coloured cappings on the Varroa tray (Figure 5) or by quickly inspecting frames in the centre of the cluster – and usually treat in November or very early December. If I cannot check visually I apply the treatment during the first extended cold spell of the winter. By treating when the colony is broodless I can be certain my intervention will have maximal effect.

What to treat with?

I have deliberately avoided – other than mentioning oxalic acid – specific miticides. Rational Varroa control involves the choice of an appropriate miticide and its correct application. Examples of incorrect or inappropriate miticide choice include; use of Apistan when resistance is known to be very widespread, use of Apiguard when the average ambient temperature is below 15°C (which makes Apiguard of little use for effective control in much of Scotland) or the use of Api-Bioxal when there is capped brood present. In addition, use of a half-dose or a reduced period of application will both reduce efficacy and potentially lead to the selection of resistance in the mite population. Used correctly – the right dose at the right time and for the right duration – the majority of the currently licensed miticides are be capable of reducing mite levels by over 90%. If they do not, use one that does. Miticide choice should be dictated by your environment and the state of the colony.

All together now

Most beekeepers grossly underestimate the movement of bees (and their phoretic mites) between colonies. Numerous studies have shown that drifting and (to an even greater extent) robbing can result in the transfer of large numbers of mites from adjacent and, in the case of robbing, more distant colonies. 

Gaffer tape apiary

Figure 6. Gaffer tape apiary …

Rational Varroa control therefore involves treating all colonies within an apiary, and ideally the wider landscape, in a coordinated manner. In communal association apiaries (Figure 6), where beekeeping experience and therefore colony management and health can vary significantly, this is particularly important. Coordinated treatment is only relevant in late summer when bees are freely flying.


Swarms originating from unmanaged or poorly managed colonies will have high mite levels. The bee population in a swarm is biased towards younger bees; these are the bees that phoretic mites preferentially associate with. Studies have shown that ~35% of the mite population of a colony leaves with the swarm.

Figure 7. Varroa treatment of a new swarm in a bait hive…

Since swarms contain no sealed brood until ~9 days after they are hived oxalic acid is the most appropriate treatment. I usually treat them using vaporised oxalic acid late in the evening soon after they are hived (Figure 7). Even casts get this treatment and I have not experienced any issues with the queen not subsequently mating successfully. I’d prefer to have a queenless low-mite colony than a queenright one potentially riddled with Varroa.

Midseason mite treatment

The text above describes the mite management strategies I have used for several years. I apply Apivar immediately the summer honey is removed and treat with oxalic acid when broodless before the end of the year. Doing this has almost never required any additional midseason treatments; if mite levels are sufficiently low at the beginning of the season they cannot rise to dangerous levels before the late summer treatment. I still get winter colony losses, but they are almost always due to poor queen mating and rarely due to Varroa and viruses.

Figure 8. Queenright splits and the window(s) of opportunity

However, if midseason treatments are required – either because there are signs of overt infestation, because regular mite counts have shown there is a problem, or to have low mite colonies after the heather honey is collected – then there are two choices. Treat with MAQS which is approved for use when there are supers on the hive and, more importantly, is effective against mites in capped cells 2. Alternatively, treat during swarm control. With care, the majority of splits (e.g. the Pagden artificial swarm or the nucleus method) can be performed to give a broodless period for both the queenright (Figure 8) and queenless partitions. That being the case, a single application of an oxalic acid-containing miticide can be very effective in controlling the mite population.


Many beekeepers complain about the cost of licensed and approved miticides. However, some perspective is needed. A colony with low levels of mites will be more likely to survive overwinter, so reducing the costs of replacement bees. In addition, a healthy colony will be a stronger colony, and therefore much more likely to produce a good crop of honey (and potentially an additional nuc). Over the last 5-6 years my miticide costs are equivalent to one jar of honey per colony per year. This is an insignificant amount to pay for healthy colonies.


Rational Varroa control requires an understanding of the goals of treatment – protecting the winter bees and minimising mite levels for the beginning of the following season – and an appreciation of how this can best be achieved using miticides appropriate for the environment and the state of the colony. Like so much of beekeeping, it involves judgement of the colony and will vary from season to season and your location. I’ve applied my midwinter treatment as early as the end of October or as late as mid-December, reflecting variation in timing of the broodless period. Rational Varroa control also involves an understanding of the biology of bees and an awareness of the influence of beekeeping (e.g. crowding colonies in apiaries which increases mite and disease transmission) on our bees. However, none of this is difficult, expensive or time consuming … and the benefits in terms of strong, healthy, productive colonies are considerable.


Queen introduction

I’m probably less qualified to write about queen introduction than almost any other aspect of beekeeping. This is not because I’ve not introduced any queens. Quite the opposite, it’s something I do more or less routinely many times a season. 

The reason(s) I’m really not qualified to discuss the topic are:

  • I almost exclusively use the method I first used and I’ve not done any side-by-side comparisons with other methods to determine which work ‘best’. I have a method that works well enough i.e. somewhere between most of the time and almost always. That’s good enough for me.
  • I’m not aware of any recent scientific studies on the subject so cannot use those to make informed decisions – or interpretations – of why some methods work and others don’t 1.

Nevertheless, not being qualified has never stopped me before 2 and it’s a topic that some beekeepers struggle with and many beekeepers worry about.

Successful introduction ...

Successful introduction …

So here goes …

Art or science?

David Cushman/Roger Patterson make the point that: 

” … you can have two colonies in the same condition, in the same apiary, on the same day and if you introduce a queen in the same condition into each, one will succeed and the other will fail.”

This doesn’t mean that 50% of introductions fail (although it reads that way). What he/they mean is that there appears to be no rhyme or reason why one succeeds and the other does not.

On another day, both might succeed … or both might fail 🙁

Is it therefore an art or a science?

I don’t know. All you can do is get the basics correct and cross your fingers …

For understandable reasons, beekeepers feel rather precious about their queens. In particular, beekeepers who do not rear their own queens (and so have no spares waiting in the wings) can get a bit paranoid about queen introduction. 

What if it goes wrong?

The colony will potentially be left irretrievably queenless and – if you purchased the queen – you’ll be £40 out-of-pocket 3.

If you do rear your own queens you can perhaps be a bit more blasé about queen introductions. Potentially you can also do the sort of side-by-side comparisons I mentioned above … though there aren’t many studies where this has been done in a rigorous way. 

Most seem to find a method that works for them and then stick with it … which is what I’ve done and what I’m going to describe.

This is what I mean by ‘get the basics correct’.

I’ll also mention an alternate method I irregularly use for what I consider to be really difficult situations and/or really valuable queens.

But before we get into the methodology, it’s worth making some general comments about the state of the recipient colony and the queen being introduced.

Is the colony really queenless?

Trying to introduce a new queen into a colony that is not actually queenless will not end well.

One or both of the queens will probably not survive the experience. Either the workers will reject (and slaughter) the incoming queen, or the queens will fight and may both be damaged and lost.

It is therefore important that the recipient colony is queenless.

By queenless I mean that there is no queen present.

I do not mean no laying queen present. If you try and introduce a new queen into a colony with a failed (non laying) queen or a virgin (unmated) queen you will have problems.

Sod’s Law is explicit in these instances … the valuable new mated laying queen will be lost 🙁

Queen above the QE

A virgin queen (in this instance on the wrong side of the queen excluder)

The very best way to be sure the colony is queenless is to remove the current queen before introducing the new one. That necessitates finding the queen in the first place. 

What if you can’t find the queen but you’re sure that the colony is queenless?

Well, there are only two possibilities if you can’t find the queen, these are:

  1. The colony is queenless … you’re good to go.
  2. The colony is not queenless … but you’ve looked so hard for so long they’re now disturbed and running manically around the frames, getting more and more agitated and angry. Neither the bees or you are any sort of state to allow the queen to be discovered. Close the hive up. Have a cup of tea. Try again tomorrow.

I discussed methods of determining whether the colony is queenright (though not by extrapolation, the opposite i.e. queenless – see below) last season. Towards the end of that post I described the addition of a ‘frame of eggs’ to determine if the colony is queenright or not. I won’t repeat all the details here.

If the colony draw queen cells on the introduced frame then you can be sure that the colony is queenless. See (1) above … you’re good to go 🙂

Not queenless, but not queenright

That same post describes the concepts of queenright and queenless.

A colony that is queenright has a mated queen capable of laying fertilised eggs (though she may temporarily not be laying, for example due to a dearth of nectar).

A queenless colony contains no queen.

But there’s an intermediate stage … or potentially two intermediate stages if you allow me a little leeway.

A colony containing a failed queen that’s either not laying at all (and not going to restart), or only laying drone (unfertilised) eggs is neither queenright not queenless. This colony will not draw queen cells on the introduced frame. You cannot safely introduce a new queen into such a colony before first finding and removing the failed queen.

A colony containing laying workers will also not 4 produce queen cells from the introduced frame of eggs. 

Laying workers ...

Laying workers …

A colony with laying workers behaves as though it’s queenright but is actually queenless. It’s not really an intermediate stage, but the consequences are the same. Again, they are highly unlikely to accept an introduced queen.

Deal with the laying workers first and then requeen … and good luck, laying workers can be a nightmare 🙁

OK … let’s assume the colony really is queenless … what’s the easiest way to introduce a new queen?

Add a sealed queen cell

Almost without exception, a queenless colony can be requeened by adding a sealed queen cell. The virgin queen will emerge, go on one or two mating flights and return and head the colony. This method of queen introduction is almost foolproof in my experience. 

Where do you get the queen cell from? Another colony, your mentor, a friend in your beekeeping association, a local queen rearer … necessity is the mother of invention 5.

Assuming the cell is a natural queen cell … cut the queen cell out of the comb with a generous amount of surrounding comb. Don’t risk damaging the queen cell. Keep it vertical … there are stages during development when the pupa is susceptible to damage. Ideally choose and use a cell 24-48 hours from emergence as they’re a lot more robust late in the development cycle.

Use your thumb to make an indentation towards the top of a frame near the centre of the broodnest, above some capped and emerging brood. Using the generous ‘edge’ of comb surrounding your chosen queen cell push this into the indentation so the cell is secure. Close up the colony and a) check for emergence in 48 hours or so 6 and b) a fortnight later for successful mating.

Adding a grafted queen to a colony

If the cell is from a grafted larvae it is even easier … press the plastic cell cup holder into the comb and push the frames together. I describe this in a recent discussion of grafting.

How successful is this method of ‘queen’ introduction?

I’d estimate at least 85%.

A very small percentage of queen cells fail to emerge (or rather, the queen fails to emerge from the cell … but you knew what I meant 😉 ).

A slightly larger percentage of queens fail to mate (or fail to return from a mating flight). But, even in a bad season, it’s rarely more than 10-15%.

The new queen is accepted by the colony because she emerged there and they all live happily ever after 😉 .


I know, I know … that’s not really queen introduction.

You’re right. But it works. Very well.

These are the two methods I use for queen introduction.

Candy-plugged queen cage

I have a large supply 7 of JzBz queen introduction and shipping cages. 

JzBz queen cages

JzBz queen cages

I really like them because they were free they are reusable, they have a tube-like entrance that can be plugged with candy/fondant and they have a central region to protect the queen from aggressive workers outside the cage. 

Some cages offer no areas of refuge for the queen and workers can damage the queen through the perforations. Avoid cages that are all perforations.

The JzBz cages can be purchased with a removable plastic cap (shown below the cage in the image). These fit over the end of the tube and can seal the cage until you judge the colony is likely to gracefully receive the new queen … as described below 8.

JzBz queen introduction and shipping cage

Using a JzBz cage for queen introduction:

  • Plug the tube of the JzBz cage with queen candy or fondant. Queen candy can be purchased commercially and kept frozen for long periods. I almost always use fondant these days as I have spare boxes of the stuff from autumn feeding.
  • Add a short piece of wire or a cocktail stick through the perforations at one end of the cage to hang the cage – entrance tube pointing downwards – between two frames. Do this before adding the queen to avoid risking skewering the queen at a later stage 9
  • Place the queen in the cage without any attendants (see below for comments on removing them). Close and seal the cage. Seal the candy tube with the plastic cap.
  • Hang the cage in the centre of the broodnest, above some emerging brood. Leave the colony for 24 hours.

The idea here is that the colony gets the chance to accept the new queen without getting the opportunity to slaughter her.

Look for signs of aggression

Colonies that have been queenless for a few hours (say 2-24) before adding the new queen are usually very willing to accept a replacement. Adding a queen immediately after removing the old queen is likely to result in some aggression to the caged queen.

Check the colony after 24 hours. I usually lift the cage out and place it gently on the top bars to observe the interaction of the workers and the queen.

Checking for aggression

If the colony show no aggression to the caged queen – look for bees trying to sting through the cage or biting at the cage – then remove the plastic cap and re-hang the cage between the frames.

If they show aggression leave them another 24 hours and check again 10

Once you remove the cap the queen will be released by the workers after they eat through the candy/fondant. This takes just a few hours. 

Check again a week later to ensure the colony has accepted the queen.

Nicot introduction cage

I use the method described above for almost every queen I introduce. 

The only exception is if I have to requeen a colony that has previously not accepted a queen using the method described above. Usually such a colony will also be broodless (just based on the timings of determining they are queenless and failing once to successfully introduce a queen). 

Under these circumstances I use a Nicot queen introduction cage.

Nicot queen introduction cages

I find a frame from another colony with a hand-sized patch of emerging brood. The comb needs to be level so that the cage can sit on top without gaps for the queen to escape.

Then do the following:

  1. Remove all the bees from the frame and place the Nicot cage over the brood using the short plastic ‘legs’ to hold it into the comb 11.
  2. Secure the cage in place using one or two elastic bands.
  3. Introduce the queen through the removable – and eminently losable 12 – door.

In practice it’s easier to do this in the order 3-1-2 … place the queen on the frame, cover with the cage and then secure it with the elastic band.

Add the frame and cage to the hive, locating it centrally. Push the frames together. 

The emerging workers will immediately accept the queen and feed her. Other workers will feed the queen through the edges of the cage.

One corner of the cage has an entrance tunnel that can be filled with candy/fondant. I don’t think I’ve ever used this. In my experience the colony releases the queen by burrowing under one edge of the cage after a few days. If they don’t, check and remove the cage a week later.

I don’t think I’ve ever failed to successfully introduce a queen using one of these cages, but it’s a relatively small sample size.

Thorne’s sell a metal mesh version of this cage that has integral ‘legs’. I’ve not used it, but the principle is the same. Keep it in a box or the sharp cut metal edges will butcher your fingers – it’s difficult picking up queens with heavily bandaged digits.

You could also ‘fold’ your own from mesh floor material. One with deeper ‘sides’ could be pushed down to the midrib of the comb, so reducing the chances of the bees burrowing under the edge of the cage.

Mated or virgin? 

I use the JzBz cage for introducing either mated or virgin queens. I’m not aware of any significant difference in the acceptance rate between them. 

However, it’s worth noting that acceptance is dependent upon essentially ‘matching’ the expectations of the colony with the state of the queen. 

A virgin queen will be less likely to be accepted by a colony from which a mated laying queen has recently been removed. Leave them 24-48 hours. 

Likewise, I remove nearly mature queen cells from a colony I’m requeening with a mated queen. I don’t want to risk an early-emerged virgin queen from ‘raining on the parade’ of the introduced queen.

I’ve only used the Nicot cage for mated queens. Since the latter is usually used for a broodless colony I want the minimum possible delay before there is new brood in the colony.

Alone or with attendants?

If you purchase a queen and receive her by post there will be a few workers caged with her.

I always remove these although some suggest that they do not adversely influence acceptance rates 13. I remove them because I’m a bit paranoid about viruses … these workers come from an ‘unknown’ hive (quite possibly not the same one that the queen came from) and will carry a potentially novel range of Deformed wing virus variants (and possibly others as well).

I don’t want these in my hive so I remove the workers

It’s also worth noting that Wyatt Mangum has an interesting report in American Bee Journal indicating that the presence of attendants significantly increases the acceptance time 14 for an introduced queen 15. In some cases the presence of attendants resulted in the colony showing aggression for longer than it took for the bees to eat through the candy plug … that’s not going to end well for the queen.

The safest way to remove attendants is to open the caged queen in a dim room with a single closed window. The bees will fly to the window (perhaps with a little encouragement).

A mated queen probably will not fly at all and can be re-caged. A virgin queen can fly well and will also end up at the window. Gently grab her by her wings and re-cage her.

You can do all this in the apiary … it requires confidence and dexterity. I know this because I recently tried it with a virgin queen in my apiary, using lashings of overconfidence and hamfistedness.

She flew away 🙁

Inevitably you can buy a gadget to help you with this – the queen muff


There is always a slight risk that queen introductions will not be successful. The queen pheromones have such a fundamental role in colony maintenance that disrupting them – or suddenly changing them – may lead to rejection. 

However, the methods described above are sufficiently successful that I’ve not found the need to look for better alternatives. They’re also sufficiently fast that I’m not tempted to try some of the ‘quick and dirty’ approaches 16 to save time.

Finally, it’s worth noting that it is usually easier to requeen a nucleus colony than a full hive. If I ever bought one of those €500 breeder queens I’d introduce her to a nuc first and then unite the nuc back with the original colony.

But that’s not going to happen 😉


DIY queen cell incubator

You can please some of the people all of the time, you can please all of the people some of the time, but you can’t please all of the people all of the time … so said John Lydgate (1370-1450).

And he wasn’t wrong.

This is something I’m particularly aware of writing a weekly post on beekeeping. Much like my talks to beekeeping associations, the ‘audience’ (in this case the readership) ranges from the outright beginner to those with way more experience than me.

An article, like the one last week, on transporting your first nuc home and transferring it to a new hive, is unlikely to be of much interest to an experienced beekeeper.

Conversely, a post on something esoteric – like Royal patrilines and hyperpolyandry – is probably going to be given a wide berth by someone who has recently started beekeeping 1.

There’s no way I can write something relevant, interesting and topical for the entire breadth of experience of the readers 2

Going by the popularity of certain posts it’s clear that many readers are relatively inexperienced beekeepers.

The post entitled Queen cells … don’t panic! contains little someone who has kept bees for five years doesn’t or shouldn’t already know 3. Nevertheless, it is one of the most popular pages over the last couple of years. It has already been read more times this year than all previous years 4.

I suspect the majority of these thousands of viewings are from new(ish) beekeepers.

If you’re in this group then I suggest you look away now 😉 5

I’m going to discuss a pretty focused and specialised topic of relevance to perhaps a fraction of 10% of all beekeepers

The 10%

When I started beekeeping I was certain I would never be interested in queen rearing.

In fact I was so certain that, when repeatedly re-reading Ted Hooper’s book Bees and Honey, I’d skip the chapter on queen rearing all together. 

By ‘queen rearing’ I mean larval selection, grafting, cell raisers, cell finishers, mini-nucs, drone flooding etc. 

Queen cells from grafted larvae … what a palaver!

What a palaver!

All I wanted was a few jars of honey.

Oh yes, and slightly better tempered bees.

And perhaps a nuc to overwinter ‘just in case’.

What about a queen or two ‘spare’ for those swarms I miss?

A year or two later I had the opportunity – through the generosity of the late Terry Clare – to learn the basics of queen rearing and grafting

A week later I had a go on my own.

Amazingly (though not if you consider the tuition) it worked 🙂 . I successfully reared queens from larvae I’d selected, transferred, produced as capped cells and eventually got mated.

It was probably the single most significant event in my experience as a beekeeper. I got my nuc to overwinter and I’ve gradually improved my bees through selecting from the best and requeening the worst. I know how to produce ‘spare’ queens, though need them less frequently as my swarm control has also improved 😉  6

I don’t know what proportion of beekeepers ‘actively’ rear their own queens. I suspect it’s 10% or less.

But even that select group aren’t the target audience for this post.

The target audience are queen rearers who need to incubate queens or queen cells for protracted periods (hours to days) without constant access to mains electricity.

Let me explain

The peripatetic beekeeper

I live on the remote west coast of Scotland 7 but keep the majority of my bees in Fife. 

My apiaries in Fife are 30-40 minutes apart, and I drive past one on my way to my main apiary (in St Andrews). If I need a ‘spare’ queen in an out apiary (and have one in St Andrews) it adds over an hour to what is already a four hour beekeeping commute.

That’s an hour of my life I’ll never get back and something I’d really like to avoid 8.

On the west coast beekeepers and bees are very thin on the ground. I’ve just started queen rearing here and (again) have a 45 minute commute between apiaries 9. I’m working with another beekeeper and larvae are sourced from one and the cells are raised in another.

You can move frames of larvae about if you keep them warm and humid – a damp tea towel works well – at least if the times/distances are not too great.

But there’s an added complication … this area is Varroa free and I don’t want to be moving potentially mite-infested frames into the area. Nor do I want to deplete any of the donor colonies of brood frames.

All I want to move are a few larvae … but they’re a lot more fragile and sensitive.

So … two slightly unusual situations.

It seemed to me that my life would be a lot easier if I had some sort of portable queen and queen cell incubator.

My trusty honey warming cabinet

More than most events in beekeeping, the timing of the various stages of queen rearing is very clearly defined. You graft day old larvae and use the cells 10 days later. This timing currently defines the dates of my trips … except that sometimes there are diary clashes.

If my apiary with the cell raising colony was a mile away I could just go later in the day. 

But it’s not … 🙁

Before I started this (temporary) life as a travelling beekeeper I’d sometimes needed to incubate queen cells that were near to emergence. Once the cell is capped you can put it in an incubator, either until you use it as a capped cell, or until the virgin queen emerges. You then requeen a colony using the recently emerged virgin queen.

This was clearly another option to make the diary clashes less of an issue – raise the cells and then incubate them (outside the hive) until emergence, and then use the queens.

I’d already used my trusty honey warming cabinet to incubate queen cells. When I built this I used an Ecostat chicken egg incubator element rather than a 100 W incandescent bulb. The Ecostat heaters are thermostatically controlled and do a pretty good job of maintaining a stable temperature, anywhere between the high 20’s (°C) and about 55°C.

A day in the life of my honey warming cabinet (click for explanation of fluctuations)

There were two minor issues … the incubator needed a 240 V mains supply and was about the size of my car 10.

Honey warming cabinet. The Apiarist

Honey warming cabinet …

However, it’s perfect if you need to incubate 800 queen cells at once 😉

What I needed was a smaller, more portable, ‘battery’ – or at least 12V – powered version … 11

Beekeepers have short arms and deep pockets

One obvious solutions was to use a commercially available hen egg incubator. Brinsea are one of the market leaders and I know several beekeepers who use them as queen cell incubators. 

Although they are usually mains powered, they actually have an integral transformer and run at 12V, so could be powered from a car cigarette lighter socket. Temperature and humidity are controlled. They start at about £80 and would need modifying to accommodate queen cells, or Nicot cages containing queens.

The beekeeping-specific commercial solution is the Carricell.

Carricell queen cell incubator

These are manufactured in New Zealand in three sizes – for 40, 70 or 144 queen cells. Swienty (and presumably others) sell the 70 cell variant 12 over here for €636 13.

Excluding VAT 🙁

Beekeepers are notoriously commendably parsimonious. Since I have an alter ego named Dr. Bodgit, it seemed logical to try and build my own.

For a little less that €636 …

And ideally less than £80 😉

But first I needed to know more about the influence of temperature on queen cell development.

Temperature and development

The usual temperature quoted for the broodnest is about 35°C. Numerous studies have shown that, although the temperature is never constant, it is always in the range 33-36°C 14

It is reasonably well known that temperature can influence the development time of honey bees. At lower temperatures, development takes a little bit longer.

More significantly, Jürgen Tautz and colleagues showed almost two decades ago that honey bee workers reared (as pupae) at low temperatures have behavioural deficiencies 15.

For example, workers reared at 32°C showed reduced waggle dance activity when compared to bees reared at 36°C. Not only were they less likely to dance to advertise a particular nectar source, but they would dance less enthusiastically, performing fewer dance circuits.

In tests of learning and memory – for example associating smells with syrup rewards – bees reared as pupae at 32°C were also impaired when compared to bees reared at 36°C.

Tautz also demonstrated that bees reared at the lower temperature were more likely to go ‘missing in action’. They disappeared at a faster rate from the hive than the bees reared at the higher temperature. This strongly suggests their compromised memory or learning also had a negative influence on their survival. For example, in predator evasion, flight duration or the ability to find the hive.

OK … so temperature is really rather important for worker development.

Perhaps very accurate thermostatic control will be needed?

But what about queens?

There are good reasons to think that queen development might not be quite as sensitive to lower temperatures.

Queen cells are relatively rarely found in the centre of the broodnest. Those that are are often considered to be ‘supersedure cells‘, though location alone is probably not definitive.

Where are queen cells more usually found?

At the periphery of the broodnest, decorating the lower edges of the frame and even protruding down into the space below the bottom of the comb.

Queen cells

Queen cells …

Logic suggests that these might well experience lower temperatures simply by being at or near the edge of the mass of bees in the cluster. 

Perhaps queen development is less temperature sensitive?

Fortunately, I don’t need to rely on (my usually deeply flawed) logic or informed guesses … the experiment has been done 16.

Chuda-Mickiewicz and Samborski incubated queen cells at 32°C and 34.5°C. Those incubated at the lower temperature took ~27 hours longer to emerge than those at 34.5°C (which emerged at 16 days and 1 hour after egg laying).

However, of the variables measured, this was the only significant difference observed between the two groups. Body weights at emergence were similar, as were the spermathecal volume and ovariole number.

In both temperature groups ~90% of (instrumentally) inseminated queens started laying eggs.

So perhaps development temperature is not so critical (for queens after all).

The cheque queen is in the post

Finally, I expected my bodged incubator would also be used to transport mated queens. There’s good evidence that these are very robust 17. After all, you can get them sent in the post 18

Again, the experiment has been done 🙂

Survival of adult drones, queens and workers at 25°C, 38°C and 42°C

Jeff Pettis and colleagues investigated the influence of temperature on queen fertility 19 and concluded that incubation within the range 15-38°C are safe with a tolerance threshold of 11.5% loss of sperm viability 20

In addition, Pettis looked at the influence of high or low temperatures on adult viability (see graph above). Queens and workers survived for at least 6 hours at 25°C or 42°C. In contrast drones, particularly at high temperatures, ‘dropped like flies’ 21.

Stand back … inventor at work

Version 1 of the incubator was built and has been used successfully.

Queen cell incubator – exterior view (nothing to see here)

It consists of a polystyrene box housing a USB-powered vivarium heating mat. This claims to offer three heating levels – 20-25°C, 25-30°C and 30-35°C – though these are not when confined in a well-insulated box where it can reach higher temperatures. I’m not sure I believe the amperage/wattage information provided and don’t have the equipment to check it.

I run it from a 2.1A car USB socket, or a similar one that plugs into the mains.

The battery pack in the picture above runs the Raspberry Pi computer that is monitoring the temperature 22. It’s important to have accurate temperature monitoring and to do some trial runs to understand how quickly the box warms/cools. In due course all this wiring can either be omitted or built in … but it wouldn’t be a proper invention unless it looked cobbled together 😉

Not a lot to see here either …

Inside the box is a lot of closed cell foam – some crudely butchered to accommodate Nicot queen cages – sitting on top of a large ‘freezer block’. This acts as a hot water bottle. There’s also a plastic tray holding some soggy kitchen towel to raise the humidity.

Define ‘success’

The box has been used for the following:

  • transfer grafted larvae from an out apiary to a cell raising colony an hour away. Success defined by getting the grafted larvae accepted by the cell raiser.
  • transport queen cells up to 7 hours by car 23. Success defined by requeening colonies with the cells.
  • transport and maintain virgin queens for 7-10 days. These emerged in the incubator and then accompanied me back and forth before being used. All are now in hives and out for mating.

While powered – either in the house or the car – the box is easy to maintain at an acceptable temperature for extended periods, though it takes some time to reach the operating temperature.

An afternoon collecting and distributing queen cells to an out apiary

Even when opening the lid as queen cells are added/removed the temperature fluctuates by no more than 2-3°C. The graph above was generated from temperature readings taking queen cells from one apiary to another.

I’ll describe maintaining queens for extended periods in an incubator (with no attendant bees) in a future post.

The future

This really is a bodged solution.

At the moment the temperature has to be changed manually to keep it within the 32-35°C range. This might only be every few hours, depending upon how frequently the box is opened.

The combination of the insulation and the ‘hot water bottle’ freezer block means it can be left unattended overnight.

However, it really needs to have automatic temperature control. This should be trivial to add but will require more time than I have at the moment and for the box to be empty. It’s accompanying me on an exotic holiday to Glenrothes for the next three days 24 and will be in use for much of July as I start to make up nucs for overwintering.

So … as promised, an inelegant but working solution for a fraction of the 10% of beekeepers who rear queens. 

At a fraction of the price of a commercial one 🙂

STOP PRESS – update 7th September ’21

I now have a working solution with proper thermostatic temperature control. It’s currently going through a final series of tests. I strongly suggest you don’t follow the botch-up design described above, but wait for another post on this subject sometime this winter. It’s possibly to build a queen cell incubator with fully automatic temperature control of ±0.5°C that will work at home or in a vehicle for about £60.

Your first bees

June is a good time to start keeping bees.

The long, cold, dark winter is a distant memory. The uncertainties of spring – the unseasonably warm days in March, the April (snow) showers, the “will they, won’t they” doubts over spring build up (in a cold year) or early swarming (in a warm one) – are over. 

If you did a ‘start beekeeping’ course in the winter then waiting until June to get bees might feel like a lifetime, but it actually makes a lot of sense.

You miss the roller coaster ride that spring sometimes provides. In a bad year, starvation or swarming can leave you without bees by the end of May 🙁

Instead, you benefit from better (more settled) weather, stronger colonies and at least three months to get to confidently work with your bees as you – hopefully – get some summer honey and prepare them for the winter ahead.

Buy local bees

There are compelling reasons to buy local bees. By this I mean queens reared locally.

More locally reared queens …

Not Greece or Italy 1, imported in large batches and dropped into a box of ‘local’ workers, all of whom will be replaced within a month. These are effectively bees from southern Europe and are quite possibly not suited to Cumbria or Essex 2.

Several scientific studies have shown that locally reared bees do better than imports, particularly when overwintering. 

But the benefits don’t end there. If you buy bees locally you’ll probably buy them from a local beekeeper 3. I’ve proposed before that this could be your mentor … and that, ideally, you could have helped split the nuc from a strong colony, watched it develop and then purchased it.

But that’s not always possible. Mentoring is time consuming and dependent on the organisation of the local beekeeping association, to say nothing of simple geographic factors 4 or Covid and social distancing.

When you buy local bees you should expect to get some of the ‘back story’ on the colony. When was the queen grafted, when did she start to lay? 

If you do agree to buy bees from a local beekeeper, don’t then go and then buy them from someone else. Preparing nucs is time-consuming and involves committing resources from honey production or making increase. At the very least, a beekeeper reserving a nuc for you probably means s/he is turning other potential purchasers away. Have some courtesy.

A 5 frame nuc when sold should contain a frame of stores, a laying queen (!) – clipped or marked if requested  – and 3-4 frames of brood in all stages.

There should be sealed brood in the colony laid by the queen heading the colony.

OK, enough preamble … what about the practicalities of getting the bees home, installing them in a hive and doing your first inspection?

Transporting bees

If you are collecting your nuc from a local apiary it will probably already be sealed up for transport. The entrance should be sealed securely and the frames should be wedged in place so they won’t flap around during transit. I use closed cell foam blocks for this, but it may not be necessary in some smaller nuc boxes.

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

You might not be provided with a strap, so bring your own. Ratchet straps are probably overkill for a nuc, but they certainly do the job. Gaffer tape works well, as do these ‘no moving parts but can I remember how they work?’ hive straps.

Standard hive straps

If you collect them at the beginning or end of the day there will be more bees in the box and fewer foragers out, er, foraging.

It’s always good to actually get the bees you’re paying for 😉

More importantly, it’s also cooler at the start or end of the day, which is one less thing to be concerned about when transporting bees. Since you’re buying locally you won’t be transporting the bees far. That being the case, it’s usually sufficient to make sure there’s good airflow under the open mesh floor, without using a travel screen.

If you move bees in the heat of the day expect to have to use some sort of mesh screen over the top of the frames. The last thing you want is overheating and stressed bees. 

Mesh and staples

Actually, that’s the penultimate thing.

The last thing you want is the combs melting and collapsing … avoid this at all costs.


Secure the nuc in the car 5 so that it can’t tip over. The frames should be in line with the direction of travel.

It’s not the end of the world if they’re perpendicular to travel, but it reduces the ‘frame flap’ when accelerating and decelerating. 

I often put the bees on the car seat, strapped in place with a seat belt, with a sheet or two of newspaper underneath the OMF to stop getting nectar or pollen on the nappa leather upholstery my filthy car from soiling the nuc box.

I’ve moved dozens of nucs like this and never had a problem.

Drive carefully.

You might find one or two bees “escaping”. In my experience these are more likely to be ‘hitchhikers’ who were underneath the open mesh floor, rather than Houdini-like bees that have circumvented the sealed entrance of the nuc 6.

Stop and let them out at the earliest opportunity … it’s safer and they’re more likely to get back to the home apiary.

If you’re 10 miles away from the apiary their fate is probably sealed 🙁

Opening the hive entrance

Bees can be a bit disoriented and distressed after a car journey.

Therefore, don’t be in a rush to open them up too soon.

I always place them in the location they are going to be permanently sited and leave them for at least half an hour.

Then, and only then, I gently open the hive entrance.

If you do it as soon as you arrive the bees may come flooding out … if you leave them to settle they will be much calmer.

Correx, the beekeepers friend ...

Correx, the beekeepers friend …

Don’t bump or rock the hive.

Don’t wrestle with the sealed entrance.

Hopefully the 30+ minutes recuperation time has allowed you to work out a strategy to open the hive entrance with the minimum disturbance possible.

Those rotating entrance disks have got a lot to commend them 🙂

Ideally you want the bees to be barely aware that the entrance is now open when it wasn’t a moment before … for example, there’s usually no need for smoke 7.

Remember, the bees know nothing about their new environment. You want them to explore it at their own pace, rather than releasing a few thousand agitated bees all at once.

Open the entrance so the bees can come and go, but don’t leave a cavernous maw gaping that they might struggle to defend,

Take a few steps back and enjoy watching the first orientation flights of your new bees.

And that’s it for the day … leave them in peace.

Transferring the nuc to a full hive

At this time of the season the bees will rapidly outgrow a 5 frame nucleus hive. If you leave them in there too long the queen will run out of space to lay and they’ll start to think about swarming.

Remember that overcrowding is one of the (many) triggers for swarming and, once they’ve decided to go, it can be very difficult to stop them.

Here's one I prepared earlier

Here’s one I prepared earlier … an overcrowded overwintered nuc in April

Therefore you need to transfer them to a full-sized hive within – at most – a few days of acquiring them 8.

You will need a full hive – floor, brood box, crownboard and roof – together with five or six (or 7 for the new Abelo boxes I see) frames with foundation fitted 9.

Frame orientation – frames from nuc in red, new foundation in grey

Since this is probably also the first time you are going to open the nuc (and, if it’s not, why did you look earlier? See the final section of this post.) you’ll also need a beesuit, hive tool and smoker.

  • Move the nuc gently to one side and place the new floor and brood box where the nuc was, with the entrance facing the same direction.
  • Gently smoke the nuc. Just a couple of puffs near the entrance should be more than sufficient. You don’t need to ‘kipper them’.
  • Transfer the 3-4 frames of brood one at a time, placing them next to each other in the new hive. By all means have a brief look at each side of the frames, but place them in the new hive in the same orientation with regard to their neighbours. The goal here is that the brood nest is not unduly disturbed.
  • Flank these with a frame or two of foundation and then add the frame of stores.
  • If I’m arranging the frames the ‘warm way’ i.e. parallel to the hive entrance, I’ll place the occupied brood frames closer to the entrance. This helps the colony defend the entrance. If the frames are perpendicular to the entrance (the cold way) I place them in the middle of the hive 10.

Add the crownboard and roof. 

All done.

Feeding the colony

Probably the first dilemma faced by a new beekeeper is whether to feed the recently re-hived nucleus colony. 

This is what beekeeping is all about … making judgement calls based upon the strength and state of the colony, in the context of the local environment and with an understanding of what the weather is going to be like over the next week or two.

Get used to it … you’ll be making a lot of decisions like this 😉

Here are a couple of scenarios …

  1. Unseasonably cold weather with lots of rain and an understrength nucleus colony.
  2. Warm, settled weather with a very strong nucleus colony in an environment with abundant forage.

The first must be fed for it to survive, let alone thrive.

The second may well not need feeding at all.

It’s best to err on the side of caution and feed nucs if there’s any doubt they will not have enough nectar to draw fresh comb and expand the brood nest. 

This spring – at least since late May – the nectar flow has been exceptional and I’ve not fed any nucs. All have drawn comb ‘for fun’, often drawing successive frames one after another that I’ve rotated into the box.

If the colony does need feeding I prefer to use a contact feeder (a plastic bucket with a fine mesh grille in the lid inverted over the brood nest) containing 1:1 (by weight) syrup made of granulated sugar and water.

Welcome to your new home … nuc ‘promoted’ to hive with contact feeder in place

The aim it to imitate a good nectar flow rather than allow the bees to store large amount of syrup stores. You want them to draw new comb and rear lots of new brood.

I place the contact feeder directly over the top bars, separated by a couple of wooden spacers. I do this because most of my crownboards lack central holes. Use a spare super to enclose the contact feeder.

I think my contact feeders are ‘half gallon’ ones … they are just big enough to take a mix of 2 litres of water and 2 kg of sugar 11. If the weather remains poor, or the nectar remains elusive (you could always ask the local beekeeper you bought the nuc from … another advantage of buying local bees 😉 ), then it will do no harm to give them a second ‘half gallon’ of syrup to help them build up.

Do not spill syrup in the apiary. It encourages robbing and your new colony may not be able to defend itself. If in doubt, again err on the side of caution … reduce the entrance size of the hive.

Inspections and enjoyment

On a warm, calm, settled day you should conduct your first colony inspection. Nucs, even recently promoted ones in a full hive, are usually a pleasure to inspect. There are sufficiently small numbers of bees that you should be able to see what’s going on relatively easily.

Don’t worry about finding the queen. If there are eggs present and no sealed queen cells then she will be in the hive.

Marked queen surrounded by a retinue of workers.

They’re not always this obvious …

It’s always a bit risky making assurances like that as I can think of several scenarios when I would be wrong.

If there are eggs present then there was a queen in the hive within the last 3 days 12.

If there are sealed queen cells present then it’s possible that the hive has swarmed.

But what about eggs being present together with unsealed queen cells?

That'll do nicely

That’ll do nicely …

There are two obvious explanations, one of which is much more likely for a new beekeeper with their first colony:

  • The colony was dead set on swarming and has swarmed without waiting for the queen cell to be sealed. This happens, but it’s unlikely to occur with a nucleus colony just moved to a new hive 13.
  • The queen has very recently died – or, more accurately, been killed – and the bees are rearing new queen cells under the emergency impulse,

New beekeepers are understandably enthusiastic … but they can be clumsy.

It’s not unusual for a queen to be damaged or killed during a colony inspection by an inexperienced beekeeper 14. It’s easy to squidge the queen between the sidebars of the frame and the brood box, perhaps because she’s rushing about after the colony was smoked too much, or between frames when returning them to the hive.

If you can’t find the queen you can’t be sure where she is.

Accidents happen.

This was almost certainly the fate of my first ever queen which disappeared a week or two after I bought my nuc … and I thought I was being so careful 🙁

Which brings me to my last couple of points. 

Do not inspect the colony more than necessary.

Once every seven days is sufficient. Don’t meddle. Let them get on with things. When they get to 7-8 frames of brood add a queen excluder and a super. 

Observe and enjoy them … from a distance. 

Congratulations … you’re now a beekeeper 🙂