Category Archives: Feeding

Mellow fruitfulness

Synopsis : Final colony inspections and some thoughts on Apivar-contaminated supers, clearing dried supers, feeding fondant and John Keats’ beekeeping.

Introduction

The title of today’s post comes from the first line of the poem ’To Autumn’ by John Keats:

Season of mists and mellow fruitfulness

The poem was written just over 200 years ago and was the last major work by Keats (1795-1821) before he died of tuberculosis. Although it wasn’t received enthusiastically at the time, To Autumn is now one of the most highly regarded English poems.

The poem praises autumn, using the typically sensuous imagery of the Romantic poets, and describes the abundance of the season and the harvest as it transitions to winter.

That’s as maybe … the last few lines of the first verse raises some doubts about Keats’ beekeeping skills:

And still more, later flowers for the bees,
Until they think warm days will never cease,
For summer has o’er-brimm’d their clammy cells.

It’s certainly true that there are late summer flowers that the bees can forage on ¹. However, he’s probably mistaken in suggesting that the bees think in any sense that involves an appreciation of the future.

And what’s all this about clammy cells?

If there’s damp in the hive in late summer then it certainly doesn’t bode well for the winter ahead.

Clammy is now used mean damp; like vapour, perspiration or mist. The word was first used in this context in the mid-17^th Century.

‘Clammy’ honey

But Keats is using an earlier meaning of ’clammy’ … in this case ’soft, moist and sticky; viscous, tenacious, adhesive’, which dates back to the late 14^th-Century.

And anyone who has recently completed the honey harvest will be well aware of how apt that definition is 😉 … so maybe Keats was a beekeeper (with a broad vocabulary).

And gathering swallows twitter in the skies

That’s the last line of ’To Autumn’ (don’t worry … you’ve not inadvertently accessed the Poetry Please website). The swallows are gathering and, like most summer migrants, already moving south. Skeins of pink-footed geese have started arriving from Iceland and Greenland.

Skein of geese over Fife

My beekeeping over the last fortnight has been accompanied by the incessant, plaintive mewing of buzzards. These nest near my apiaries and the calling birds are almost certainly the young from this season.

A few nights ago, while hosing the extractor out in the bee-free-but-midge-filled late evening, I was serenaded by tawny owls as the adults evicted their young from the breeding territory in preparation for next season.

These are all signs, together with the early morning mists, that summer is slipping away and the autumn is gently arriving.

Morning mist clearing over the loch

The beekeeping season is effectively over and all that remains is preparing the colonies for winter.

Supers

All the supers were off by the 22^nd of August. There was still a little bit of nectar being taken in but the majority was ripe and ready. As it turns out there was fresh nectar in all the colonies when I checked on the 10^th of September, but in such small amounts – no more than half a frame – that it wouldn’t have been worth waiting for.

At some point you have to say … enough!

Or, this year, more than enough 🙂 .

Most of the honey was extracted by the end of August. It was a bonanza season with a very good spring, and an outstanding summer, crop. By some distance the best year I’ve had since returning to Scotland in 2015.

Of course, that also meant that there were more supers to extract and return and store for the winter ahead.

Lots of lifting, lots of extracting and lots of buckets … and in due course, lots of jarring.

Storing supers wet or dry?

In response to some recent questions on storing supers wet or dry I tested ‘drying’ some.

I’ve stored supers wet for several seasons. I think the bees ‘like’ the heady smell of honey when they are added back to the hives for the spring nectar flow. The supers store well and I’ve not had any problems with wax moth.

However, this year I have over two full carloads of supers, so – not having a trailer or a Toyota Hilux ² – I have to make multiple trips back to put them in storage ³. These trips were a few days apart.

I added a stack of wet supers to a few hives on the 1^st of September and cleared them on the 9^th. All these supers were added over an empty super (being used as an eke to accommodate a half block of fondant – see below) topped with a crownboard with a small hole in it (no more than 2.5 cm in diameter, usually less).

Converting wet supers to dry supers – note the crownboard with a small central hole

When I removed the supers on the 10^th they had been pretty well cleaned out by the bees. In one case the bottom super had a very small amount of fresh nectar in it.

So, 7-8 days should be sufficient for a strong colony to clean out 3-4 supers and it appears as though you can do it at the same time as feeding fondant … result 🙂 .

Feeding fondant

I only feed my colonies Baker’s fondant. I add this on the same day I remove the honey-laden supers. I’ve discussed fondant extensively here before and don’t intend to rehash the case for its use again.

Oh well, if you insist 😉 .

I can feed a colony in less than two minutes; unpacking the block, slicing it in half and placing it face down over a queen excluder (with an empty super as an eke) takes almost as much time to write as it does to do.

Take care with sharp knives … much easier with a slightly warm block of fondant

But speed isn’t the only advantage; I don’t need to purchase or store any special feeders (an Ashforth feeder costs £66 and will sit unused for 49 weeks of the year). I’ve also not risked slopping syrup about and so have avoided encouraging robbing bees or wasps.

I buy the fondant through my association. We paid £13 a block this year (up from about £11 last year). That’s more expensive than making or buying syrup (though not by much) and I don’t need to have buckets or whatever people use to store, transport and distribute syrup. Fondant has a long shelf life so I buy a quarter of a ton at a time and store what I don’t use.

All gone! 12.5 kg of fondant added on 22/8/22 and photographed on 9/9/22

And, contrary to what the naysayers claim, the bees take it down and store it very well.

What’s the biggest problem I’ve had using fondant?

The grief I get when I forget to return the breadknife I stole from the kitchen … 😉 .

Apivar-contaminated honey and supers

Last season I had to treat a colony with Apivar before the supers came off. This was one of our research colonies and we had to minimise mite levels before harvesting brood.

I’ve had a couple of questions recently on what to do with supers exposed to Apivar … this is what I’ve done/will do.

Apivar

The Apivar instructions state something like ’do not use when supers are present’ … I don’t have a set of instructions to check the precise wording (and can’t be bothered to search the labyrinthine VMD database).

Of course, you’re free to use Apivar whenever you want.

What those instructions mean is that honey collected if Apivar is in the hive will be ’tainted’ and must not be used for human consumption.

But, it’s OK for the bees 🙂 .

So, I didn’t extract my Apivar-exposed supers but instead I stored them – clearly labelled – protected from wasps, bees and mice.

This August, after removing the honey supers I added fondant to the colonies. In addition, I added an Apivar-exposed super underneath the very strongest colonies – between the floor and the lower brood box.

I’ll leave this super throughout the winter. The bees will either use the honey in situ or will move it up adjacent to the cluster.

In spring – if I get there early enough – the super will be empty.

If I’m late they may already be rearing brood in it 🙁 … not in itself a problem, other than it means I’m flirting with a ridiculous ’double brood and a half’.

Which, of course, is why I added it to the strongest double brood colonies. It’s very unlikely the queen will have laid up two complete boxes (above the nadired super) before I conduct the first inspection.

But what to do with the now-empty-but-Apivar-exposed supers?

It’s not clear from my interpretation of the Apivar instructions (that I currently can’t find) whether empty supers previously exposed to Apivar can be reused.

WARNING … my reading might be wrong. It states Apivar isn’t to be used when honey supers are on but, by inference, you can use and reuse brood frames that have been exposed to Apivar.

Could you extract honey from brood frames that have previously (i.e. distant, not immediate, past) been Apivar-exposed?

Some beekeepers might do this ⁴.

It’s at this point that some common sense it needed.

Just because re-using the miticide-exposed supers is not specifically outlawed ⁵ is it a good idea?

I don’t think it is.

Once the bees have emptied those supers I’ll melt the wax out and add fresh foundation before reusing them.

My justification goes something like this:

Although amitraz ⁶ isn’t wax-soluble a formamidine breakdown product of the miticide is. I have assumed that this contaminates the wax in the super.
I want to produce the highest quality honey. Of course this means great tasting. It also means things like wings, legs, dog hairs and miticides are excluded. I filter the honey to remove the bee bits, I don’t allow the puppies in the extracting room and I do not reuse supers exposed to miticides.
During a strong nectar flow bees draw fresh comb ‘for fun’. They’re desperate to have somewhere to store the stuff, so they’ll draw out comb in a new super very quickly. Yes, drawn comb is precious, but it’s also easy to replace.

Final inspections

I conducted final inspections of all my colonies in Fife last weekend ⁷.

For many of these colonies this was the first time they’d been opened since late July. By then most had had swarm control, many had been requeened and all were busy piling in the summer nectar.

Why disturb them?

The queen had space to lay, they weren’t likely to think about swarming again ⁸ and they were strong and healthy.

Midsummer inspections are hard work … lots of supers to lift.

If there’s no need then why do it?

Of course, some colonies were still busy requeening, or were being united or had some other reason that did necessitate a proper inspection … I don’t just abandon them 😉 .

I don’t just abandon them … introducing a queen to a nucleus colony

But now the supers were off it was important to check that the colonies were in a suitable state to go into the winter.

I take a lot of care over these final inspections as I want to be sure that the colony has the very best chance of surviving the winter.

I check for overt disease, the amount of brood in all stages (BIAS; so determining if they are queenright) and the level of stores.

And, while I’m at it, I also try and avoid crushing the queen 🙁 .

Queenright?

I don’t have to see the queen. In fact, in most hives it’s almost impossible to see the queen because the box is packed with bees. If there are eggs present then the queen is present ⁹.

But, there might not be a whole lot of eggs to find.

Firstly, the queen is rapidly slowing down her egg laying rate. She’s not producing anything like 1500-2000 eggs per day by early autumn.

A National brood frame has ~3000 cells per side. If you find eggs equivalent in area to one side of a brood frame she’s laying at ~1000/day. By now it’s likely to be much less. At 500 eggs/day you can expect to find no more than half a frame of eggs in the hive.

Remember the steady-state 3:5:13 (or easier 1:2:4) ratio of eggs to larvae to pupae? ¹⁰

Several of my colonies had about half a frame of eggs but significantly more than four times that amount of sealed brood … clear evidence that the laying rate is slowing dramatically.

The shrinking brood nest – note the capped stores and a little space to lay in the centre of the frame

Secondly, the colony is rapidly filling the box with stores, so reducing the space she has to lay. They’re busy backfilling brood cells with nectar.

Look and ye shall find …

So I focus carefully on finding eggs. I gently blow onto the centre of the frames to move the bees aside and search for eggs.

In a couple of hives I was so focused on finding eggs that – as I prepared to return the frame to the colony – I only then saw the queen ambling around on the frame. D’oh!

Some colonies had only 3-4 frames of BIAS, others had lots more though guesstimating the precise area of brood is tricky because of the amount of backfilling taking place.

I still need to check my notes to determine whether it’s the younger queens that are still laying most eggs … I’d not be surprised.

Stores

Boxes are now heavy but not full. All received (at least) half a block of fondant in late August and more last weekend. There’s also a bit of late nectar. The initial half block was almost finished in a week.

Once the bag is empty I simply peel it away from the queen excluder. If you’re doing this, leave the surrounding super in place. It acts as a ‘funnel’ to keep the thousands of displaced bees in the hive rather than down your boots and all over the floor.

Although the bees were flying well, the bees in and around the super were pretty lethargic. I’ve seen this before and am not concerned. I don’t know whether these are bees gorged with stores, having a kip or perhaps young bees that don’t know their way about yet. However, it does mean that any bees dropped while removing the bag tend to wander aimlessly around on the ground.

I’d prefer they were in the hive, out of the way of my size 10’s.

If you look at many of the frames in the hive they will be partially or completely filled with stores. The outer frames are likely to be capped already.

An outer frame of capped stores

These frames of stores are heavy. There’s no need to look through the entire box. I simply judge the weight of each frame and inspect any that are lighter than a full frame of stores.

Closer to the brood nest you’ll probably find a frame or two stuffed, wall-to-wall, with pollen. Again, a good sign of a healthy hive with the provisions it needs to rear the winter bees and make it to spring.

Disease

The only sign of disease I saw was a small amount of chalkbrood in one or two colonies. This is a perennial situation (it’s not really a problem) with some of my bees. Quite a few of my stocks have some (or a lot of) native Apis mellifera mellifera genes and these often have a bit of chalkbrood.

I also look for signs of overt deformed wing virus (DWV) damage to recently emerged workers. This is the most likely time of the year to see it as mite levels have been building all season and brood levels are decreasing fast. Therefore, developing brood is more likely to become infested and consequently develop symptoms.

Fortunately I didn’t see any signs of DWV damage and the initial impression following the first week or so of miticide treatment is that mite levels are very low this season. I’ll return to this topic once I’ve had a chance to do some proper counts after treating for at least 8-10 weeks (I use Apivar and, since my colonies all have medium to good levels of brood, the strips need to be present for more than the minimum recommended 6 weeks).

Closing up

Although these were the last hive inspections, they weren’t the last time I’ll be rummaging about in the brood box.

At some point during the period of miticide treatment I’ll reposition the strips (adjacent to the ever-shrinking brood nest) having scraped them to maximise their effectiveness.

Apivar scratch and sniff repositioning studies

However, all that will happen in a month or so when I can be reasonably sure the weather will be a lot less benign. Far better to get the inspections out of the way now, just in case.

So, having added the additional fondant (typically half a block) I closed the hives, strapped them up securely and let them get on with making their preparations for the coming winter.

Goodbye and thanks for the memories

There’s a poignancy about the last hive inspections of the season.

The weather was lovely, the colonies were strong and flying well, and the bees were wonderfully placid. It’s been a great season for honey, disease levels are low to negligible and queen rearing has gone well ¹¹.

But it’s all over so soon 🙁 .

Hive #5 (pictured somewhere above … with the empty bag of fondant) was from a swarm control nuc made up on the last day of May (i.e. a 2021 queen). It was promoted to a full hive in mid-June. At the same time, while the hive they came from (#28) was requeening I’d taken more than 20 kg of spring honey from it. The requeening of #28 took longer than expected as the first was almost immediately superseded. Nevertheless, the two hives also produced almost 4 full supers (conservatively at least 40 kg) of summer honey.

Good times 🙂 .

My notes – for once – are comprehensive. Over the long, dark months ahead I’ll be able to sift through them to try and understand better ¹² what went wrong.

That’s because – despite what I said in the opening paragraph of this section – there were inevitably any number of minor calamities and a couple of major snafu’s.

Or ’learning opportunities’ as I prefer to call them.

Last light over Rum and Eigg … not a bad view when visiting an out apiary

But that’s all for the future.

For the moment I have a sore back and aching fingers from extracting for days and the memory of a near-perfect final day of proper beekeeping.

It’s probably time I started building some frames 🙁

Mini-nucs: tips and tricks

Introduction

A couple of weeks ago I described some of the basics of using mini-nucs for queen mating. I’ll try and avoid overlaps with that post in the following discussion of ‘tips and tricks’, effectively a rag-bag collection of stuff I failed to cover last time, interspersed with some typical problems that might be encountered.

Inevitably some of the discussion will be about specific modifications to the particular mini-nucs I use (Kieler or Warnholz polystyrene mating nucs). I settled on these because I needed a dozen one season, I had zero experience in using any so had nothing to compare and I couldn’t afford Apidea’s.

Kieler mini-nucs: four topbar frames and an integral feeder

Overall I’ve been reasonably satisfied with the choice my younger, poorer ¹ and (even more) ill-informed self made. Over a decade later I’m using the same mini-nucs and I’ve not been tempted to try anything else ².

Nevertheless, despite a Kieler-centric flavour to some of the comments below, most still apply directly (or with a little finagling) to other makes of mini-nuc.

Finally, I’ll repeat the point I made last time … mini-nucs are ’high maintenance’. They are not ’fit and forget’ beekeeping. Unless placed in the shade they may well abscond on a lovely day ³. Late in the season, without care and attention, they can get robbed out by wasps in hours. If there’s no nectar flow they will need feeding.

But, looked after carefully, they can be an efficient way to get queens mated .

Painting and decorating

Any poly hive needs painting to protect it from UV degradation. Most of my mini-nucs were first painted with el cheapo masonry paint. This has a matt finish and has been reasonably hard wearing.

More recently, I’ve started painting – or overpainting – them with Hammerite garage door paint. This is an oil or solvent based gloss paint. It causes the surface of the polystyrene to melt (very slightly) and therefore bonds extremely well. The Swienty brood boxes I painted several years ago look as good now as they did then. The Hammerite paint comes in a range of colours, including a rather nice green or blue.

Hammerite Oxford blue, since you asked

Successful queen mating needs reasonable weather (and patience). However, it also needs the returning mated queen to successfully find the mini-nuc she set out from. It therefore makes sense to either place the mini-nucs in separate and distinctive locations, or (perhaps that should be and/or) to paint them in distinctive colours.

Red ‘Wilko’ masonry paint and ‘bin end’ yellow gloss

I tend to place mine in pairs and so often have a plain and coloured one on the same stand, facing in opposite directions to further help the queen discriminate between entrances.

Entrances and exits

Kieler-type mini-nucs have a rotatable entrance with three or four options – blanked off, ventilation, a queen excluder or fully open. I shouldn’t need to mention that, if there’s a virgin queen in the hive (that you want mated), the entrance must be fully open.

But I will 😉

Entrance discs for mini-nucs

You can purchase replacement entrance disks like those in the photo above from a range of suppliers (or eBay, which is significantly less expensive). Using these may help queens return to the correct mini-nuc after orientation or mating flights.

Oops, almost forgot … bees have a tendency to nibble away at the polystyrene around the entrance of these Kieler nucs (or at the ‘under entrance’ which I’ve never used) while confined. It’s therefore worth painting the entrance tunnel as well as the outside.

Crownboards

Apidea’s and several other mini-nucs I’ve looked at are sold with clear semi-rigid plastic crownboards. Some have integral flaps for adding the queen cell or feeding the mini-nuc without letting clouds of bees escape (admittedly small clouds, as they’re only primed with a few hundred millilitres of bees).

Kieler’s are sold without a crownboard. Don’t let that put you off. A thick piece of clear plastic works just fine as a crownboard and you can easily engineer (i.e. cut) a small flap to add the queen cell between the topbar frames. I use a small piece of tape to hold in down.

Plastic crownboard. Note flaps for adding the queen cell and (above the feeder) adding syrup

You can put an additional small flap above the feeder that allows you to add syrup without any bees escaping. This only needs to be a few millimetres square and doesn’t need taping down. Even if you don’t think you’ll be feeding syrup – which you do using a small funnel – this modification takes seconds and won’t be in the way (but you’ll be glad it is there if you need it).

Hold the crownboard in place with drawing pins. That way there’s less chance it will blow away should you open the box on a windy day. It also means the crownboard stays stuck to the brood body, rather than being removed with the tightly-fitting roof.

Feeder mods

The Kieler integral feeder has some good and bad points.

It’s a good size, so reducing the chance of the mini-nuc starving if left for an extended period. However, this inevitably cuts into the space available for bees and brood, meaning that retention of the feeder can lead to rapid overcrowding.

You win some, you lose some!

The feeder is easy to remove and only fits in one orientation. Irritatingly it is too deep to fit into the ‘second storey’ extension (see below). It also has no cover or queen excluder and the queen can sometimes end up in the feeder, particularly if the bees build comb there.

Feeder with queen excluder

I therefore usually fit a small rectangle of plastic queen excluder, balanced on map pins stuck into the inner walls of the feeder. This stops the queen entering the feeder, but doesn’t necessarily stop the bees building comb there.

Be thankful for small victories … 😉

If you need more brood space you can easily replace the integral feeder with a homemade frame feeder designed to feed fondant. I build these shorter than the integral feeder so that they can be used interchangeably in the ‘second storey’ extension.

Kieler frame feeders

These work well, cost pennies to make and can be quickly exchanged when needed. When I’ve overwintered queens in these mini-nucs I’ve always used these fondant frame feeders in the upper storey, with frames filling the entire lower level. This reduces disturbance when you need to feed them.

Frames

The Kieler is a mini-topbar hive. Each topbar has a longitudinal slot cut into its underside designed to take a strip of foundation. They also have a ‘pinched’ central area, so that a queen cell can be easily inserted between two adjacent bars.

The bars themselves are just 15 x 8 mm softwood. Purchased separately they cost 36 p each (Yikes! … and those don’t even appear to have the central pinched indent).

If you need more (and you will … to replace losses and for the the upper storey should you buy one) just make your own with some wood from the store, a metal ruler, a Stanley knife and some antiseptic cream and Elastoplast.

And, while you’re at it, don’t go fiddling about with little strips of foundation held in place with melted wax. I did this for years. They work perfectly well, but they are fragile. The foundation in unused topbar frames will get bent or broken, and then you’ll have to start all over again.

Instead, eat as many Fruit Splits, Rocket lollies or Twister’s as you can stomach ⁴ and keep the sticks. Split these lengthwise and glue them into the longitudinal slot in the Kieler topbar using normal wood glue and ⁵ never re-wax them again.

Kieler mini-nuc topbar frames – no need for foundation or waxing

And, no, you don’t need to cover them in melted wax or anything else. All the bees need is a guide to help them draw the comb in the right place.

I’m sure there’s stuff I’ve forgotten about, but that lot will do for the moment. Let’s move on to four specific practical aspects of using mini-nucs.

Judging queen quality

You can’t … or at least I can’t.

I don’t think you can meaningfully determine the quality of the queen in a mini-nuc. The time between when she starts laying and when she runs out of comb is sometimes too short to even check whether she’s producing worker brood.

I usually leave her in the box until there’s some capped worker brood present and then – ideally – move her to a 2-5 frame nucleus colony. At the same time I clip and mark her. As long as she’s laying one egg per cell (and she sometimes starts laying more than this, but should slow down after a day or so) and the brood develops into worker brood then things should be OK.

However, it’s not until she’s laid a full frame or three of brood that you can judge the laying pattern (remembering that the laying pattern may also depend upon the bees in the box with her).

Brood frame with a good laying pattern

Furthermore, to properly judge her you need to observe the behaviour of the bees that develop from the eggs she lays.

Are they well tempered? Are they steady on the comb? Do they have the other traits you are keen to promote? Frugality? Good pollinators? Preferential collection of avocado nectar (Afik et al., 2010).

OK, perhaps not the last of those, but you’d be surprised about the traits some beekeepers favour.

Queen introduction

I remove the mated queen from the mini-nuc, place her in a JzBz cage without attendants and introduce her in the usual way to a queenless full-frame nucleus colony; I leave the sealed cage hanging between frames overnight and – assuming there are no signs of aggression to the caged queen – I remove the plastic cap and leave the workers to eat their way in through the fondant-plugged entrance/exit tube.

If there are signs of aggression, leave it another 24 hours.

Checking for aggression

A well designed introduction cage has some protection for the queen so she can avoid aggressive workers that can otherwise damage her feet. I’ve had considerable success with the JzBz cages (and happen to have inherited a bucket full and so don’t use anything else 😉 ).

I’ve inadvertently left a queen trapped in one of these cages for 6 days with no ill effects. Don’t rush things.

Rear some spares

What do you think happens with commercially reared queens, many or most of which are mated from mini-nucs?

Exactly … nothing, other than being popped into a shipping cage and having a £40 price tag attached.

In contrast, you have the opportunity to check your queens more thoroughly.

Rear a few more than you need, check out their performance, keep the best and donate the unwanted to one of the many, many beekeepers clamouring for queens – particularly late in the season. Even the also-rans are likely to be OK ⁶. Not necessarily great, but more than good enough to get the colony through to the next season ⁷.

Queen rearing diary; automagically populates days and events

And finally, make sure you keep good records. The first couple of times you do this you’ll think you will be able to remember the key points the following year; the dates of emergence, the time it took to have mated queens, the origin of the queen cell used to prime the mini-nuc etc.

But you probably won’t. The notes will be very useful for planning your queen rearing the following season.

Keeping things going

Populating mini-nucs early in the season is often a thankless and unpleasant task. The weather is cool, the bees are tetchy and – as described a fortnight ago – you may have had to shake through the colony twice to get the young workers.

That’s not the sort of task I like to repeat if I can possibly avoid it.

If you’re rearing queens all through the summer you can simply remove one mated queen and, shortly afterwards (within a few hours), add a new mature queen cell. This is the ideal situation and, with good organisation, good weather and good mating success, you can get three or four queens out of a single mini-nuc in one season.

Mainly good organisation.

You need to ensure you have a succession of mature queen cells ready at the about right time, remembering that queen mating often takes longer than expected (or wanted).

Scrub ‘caretaker’ queens

If that’s not possible, or if you want (or have) to interrupt queen cell production (e.g. your queenright cell starter swarms or a round of grafting fails) you can remove the mated queen from the mini-nuc and allow the bees to rear a ‘scrub’ queen.

A well populated mini-nuc will readily do this. The resulting queen is usually a bit on the small side, but she will keep the worker population ticking over and ready to accept a new mature queen cell in due course. In addition, the enforced brood break while they rear the scrub queen helps prevent the mini-nuc from getting too overcrowded.

These ‘caretaker’ queens are reared under the emergency response and – assuming there are suitable eggs in the little colony – emerge about 15 days after you remove the mated queen (remember, the bees preferentially choose 3 day old eggs to rear queens under the emergency response). A fortnight or so later the queen should be mated and laying. This approach therefore means you can take 4-6 weeks off if needed.

The end of the queen rearing season

What do you do with the contents of the mini-nuc after you’ve taken the last of the mated queens out? The little hive may well be bursting with bees, with all 4-6 combs containing brood.

Many beekeepers shake the bees out in front of a strong hive. The majority of the workers will be accepted, but the brood is wasted.

To avoid this I’ve used ‘zip’ ties to secure two Kieler topbar frames into a standard brood frame. At the very least these can be placed into a full sized hive for the brood to emerge. Usually, by the time of year I get round to this the bees have stopped drawing comb. Once the brood has emerged I move the frame to the side of the brood box and remove it.

Dave Cushman has details of some clever frame modifications that allow Kieler-type (he calls them Kirchhain mating hives) frames to be drawn at the beginning of the season and used to accommodate brood-filled frames at the end.

Unsurprisingly, when I’ve done this it’s been a lot more ’Heath Robinson’. The Kieler topbar frames are a little too long to fit end-to-end in a National frame. I therefore built some with a scrap 8 mm thick spacer (shown in black below) tacked under one side of the frame. I then use zip ties to hold everything more or less in place.

Using mini-nuc brood frames

Despite being a total bodge this has generally worked well. I’m pleased not to waste the brood.

Now I know the air freshener trick (described in this 2020 post) I’d probably just add the frames as shown in the diagram above together with the adhering bees, and give them and the recipient colony a quick blast of ’Sea breeze’ before uniting them.

Overwintering mini-nucs

Alternatively, with a little care you can overwinter queens in mini-nucs. This saves you the faff of emptying them at the end of the season, and means they are ready for queen cells the following year (after removing the queen of course) ⁸.

I’ve overwintered queens successfully quite a few times but certainly don’t consider myself an expert at it. There’s quite a high attrition rate. Remember how small these colonies are, how limited the space is for stores and the relatively small population of bees present to stop the colony freezing in the winter.

I think every mini-nuc I’ve overwintered successfully has been a double-decker, with the standard Kieler brood box underneath an additional extension brood body. These almost double the volume of the mini-nuc.

The mini-nuc needs to be strong in mid/late autumn, almost certainly boosted by combining the contents of two separate mini-nucs. You can unite them over paper in the same way you’d treat a full sized hive.

Unfortunately, the upper and lower brood boxes have different depths, so comb drawn in the bottom box needs to be trimmed to fit in the upper box. A messy and irritating task.

I replace the lower integral feeder with additional brood frames and place one or two fondant frame feeders in the upper chamber – usually one at either end to ensure the mini-cluster is near to one of them.

Place the box somewhere sheltered, leave the entrance open to allow the bees to fly for cleansing flights and cross your fingers …

Gimme shelter

I’ve not overwintered mini-nucs since returning to Scotland, though I know several beekeepers here who do this successfully. In the Midlands we often had quite harsh winter weather – certainly much colder than we usually get here on the north-west coast of Scotland.

Two double decker mini-nucs overwintered successfully in an unheated greenhouse

A decade ago, well before my bee shed experiments, I was successfully overwintering mini-nucs in an unheated greenhouse with entrance tunnels from the hive to the outside. These worked surprisingly well and got queens through some really hard weather (note the snow in the picture above – late March 2013).

Tunnel entrances to overwintered mini-nucs

If the winter was particularly severe I would cover the mini-nucs with a thick layer of bubble wrap to try and retain as much warmth as possible. The levels of stores needs to be checked regularly, particularly once brood rearing starts in earnest. These little colonies can starve surprisingly quickly 🙁 . It takes seconds and causes minimal disruption to swap out those fondant frame feeders.

With a little luck and the normal amount of good judgement it was sometimes possible to remove the overwintered queen to make up a nuc in mid/late April, replacing her with a queen cell from the first round of grafting.

Of course, it rarely worked quite as smoothly as that … 😉 ⁹

Finally

The one thing I would not recommend you try is allow the mini-nuc to build up to a full-sized nuc without supplementing it with additional brood and bees. A mini-nuc is too small and it will take too long rearing a few hundred bees at a time to make even a five frame nuc. I’ve tried and it’s a waste of effort.

References

Afik, O. et al. (2010) ‘Selection and breeding of honey bees for higher or lower collection of avocado nectar’, Journal of Economic Entomology, 103(2), pp. 228–233. Available at: https://doi.org/10.1603/ec09235.

Winter weight

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Synopsis: With colonies now rearing brood there is a risk of them starving. Here are a couple of ways of checking the winter hive weight to determine if you need to add fondant. These checks should be conducted every 2-3 weeks until the bees are foraging in the warmer spring weather.

Introduction

Last week I described how to determine what was happening inside the hive in winter.

By carefully inspecting the debris that falls through the open mesh floor (OMF) you can tell:

the size and position of the cluster,
whether they are rearing brood (or, more precisely, whether there is brood being uncapped … I don’t think you can tell if there is open brood simply by inspecting the debris),
if frames of stores distant from the cluster are being used.

In addition, I explained the importance of checking that the hive entrance was clear of corpses. These accumulate during long periods of cold or inclement weather. If the hive entrance is small enough to prevent mice from getting in – and it should be – then there’s a chance these corpses will build up sufficiently to stop bees getting out.

Entering the ‘danger zone’ – rearing brood, too cold to forage – don’t let them starve

These two checks take no more than a few minutes and should be conducted at least monthly. There’s no harm in doing them more frequently because – performed correctly – the colony isn’t disturbed at all.

Last week I described these as ”The bees don’t even know they’re being checked” checks.

The final important winter check is to determine the weight of the colony.

Avoirdupois ¹

If the bees are rearing brood they will be using their winter stores. Of course, they will have been using these stores throughout the late autumn and winter, but critically, the rate at which they use their stores will increase once brood rearing starts.

I’ve illustrated this before schematically, but have attempted to improve the diagram a little this year.

Once they have reared some brood, they’ll have more bees to help them rear some more brood, meaning that the rate at which the stores are used will increase.

Schematic diagram of winter hive weights

The solid black line is the weight of the colony. In the late autumn the colony almost certainly goes through a broodless period ². During this broodless period the colony is simply using stores to maintain the adult bees in the cluster. I’ve drawn this as a straight line (i.e. a constant rate of stores usage), but I bet it varies with the ambient temperature as more or less stores are required for essential metabolic processes.

But at some point the queen starts laying again and the colony have some larvae to feed.

I’ve indicated the start of brood rearing by a dashed vertical line. Typically I usually guesstimate this occurs around the winter solstice ³, but for our purposes the precise timing is irrelevant.

Twenty one days later these bees emerge, by which time the queen has already laid some more eggs.

Things start to pick up.

What started as a small palm-sized patch of brood now covers almost the side of a frame, in a month it will be double that.

Or more.

And all of those hungry mouths mean more stores are needed, so the rate at which the stores are consumed will increase, meaning that the colony weight will decrease … and it will continue to get lighter faster ⁴.

Silent spring

A few crocus and snowdrops are out, but the weather is too poor for foraging.

The weather gradually improves and more spring flowers become available.

There’s gorse available, of course. There always is.

Late December gorse …

The bees can now forage a little more. On unseasonably warm days the bees take cleansing flights and might collect a little pollen and nectar.

I’ve imaginatively and artistically illustrated this in the graph with some little yellow flowers 🙂

But, all the time, more brood is being reared.

If the nectar coming in is insufficient to feed the brood – and early in the season it will be – then the bees will continue to make inroads into their precious stores.

And the colony will get lighter.

And lighter.

Until it drops below some critical threshold and enters the ‘danger zone’ – the absolute weight doesn’t matter ⁵ – at which point the colony must go into self-preservation mode.

Brood will be abandoned, cannibalised and/or ejected from the hive. The queen will stop laying. The colony will be forced back into a ‘maintenance’ state.

A protracted cold period, or a fortnight of rain, and there’s a very real danger the colony will starve to death.

At the very best the early spring expansion of the colony will be severely retarded and it is unlikely to recover until mid-season.

All of which is easily avoided by carefully monitoring the amount of stores the colony has.

A brood frame full of stores

However, remember you’re supposed to be conducting ”The bees don’t even know they’re being checked” checks, not pulling open the brood box and rummaging through to count frames of sealed stores.

But since the number of bees in the colony is steady (or likely decreasing slowly) and there’s effectively no nectar being collected, the weight of the hive is a good surrogate measure to determine the level of stores available.

Winter weight

There are all sorts of ingenious solutions to determine the weight of a full hive.

Probably the most complicated and expensive is to purchase (or build) a set of electronic hive scales that automagically communicate with an app on your smartphone to give you a real-time readout of the hive weight in kilograms. You can record the weight of a few thousand foragers leaving the hive in the morning ⁶, and see them return by nightfall together with the 1500 g of nectar they’ve collected.

Arnia hive data

At the other end of the spectrum – in terms of both cost and information – is hefting the hive. Using nothing more than than a gentle lift and good judgement you can readily tell whether the hive contains sufficient stores for the bees to continue to rear brood. You won’t be able to tell the exact weight of the hive, but you will be able to determine whether it weighs enough.

I’ve used both methods.

However, I routinely only do the latter.

I’ll leave a discussion of automated hive monitoring to another day ⁷ and will instead briefly discuss two methods that are quick, cheap and easy (choose any three).

One method – hefting the hive – costs nothing, but requires a bit of experience and judgement. The second method involves – inaccurately, but reproducibly – weighing the hive. This costs about £10 to implement and provides a good way to build up your confidence that your hive hefting is probably good enough to ensure colony survival.

And good enough is probably all you need …

Hefting the hive

This is easier to show than describe:

The general idea is that you judge how much effort is required to lift one edge of the hive – typically the back – a couple of centimetres off the hive stand. As you can see from the video, other than slackening off the strap that secures the hive to the stand ⁸ there’s nothing else involved.

Comparisons help here.

It helps to have the ‘muscle memory’ of how much the hive weighed last time you checked, or – even better – how heavy it should feel like at this stage of the winter.

Both come with experience, and improve with lots of experience.

If you have several hives in the apiary, all with the same hardware, then hefting one after the other makes this comparison relatively easy. If – like in my apiaries – you have a range of different roofs, it can help to remove the roof to get a better ‘feel’ for the hive weight.

The hive should feel heavy.

If the hive feels light it probably is light.

Too light.

Weighing the hive

This second method is a little bit more involved.

I’ve previously recommended using a set of luggage scales to weigh the hive. You attach them to one edge of the hive floor, pull up gently, let the weight stabilise and then record the value on the digital display.

Don’t try this using luggage scales with an analogue display, or ones that don’t emit a helpful ‘beep’ and freeze the display when the weight stabilises.

Just don’t 🙁

Suitable luggage scale cost about a tenner. Mine are very friendly but cannot spell.

Friendly scales …

However, those of you who have tried this method will be aware of the world of grief that is encapsulated in the words ”let the weight stabilise”, particularly if you do not have a lot of upper body/arm strength.

Here’s the problem … you are trying to hold half the weight of a full hive stationary. Probably ⁹ your arms will be bent at the elbow.

The hive will probably weigh 30+ kg.

Even half that is a lot to hold steady while you wait for the tinny electronic ‘beep’ to tell you to relax and lower the hive gently back onto the hive stand.

I struggle to do this (more now than I used to) and I’m tall and relatively strong.

Before I explain an easier way to achieve the same thing I ought to say a couple of words about determining the total hive weight.

Physics … Ewwww!

If everything – frames, bees, stores – in the hive are evenly distributed, then opposite sides of the hive (weighed as described above) will be a fraction less than half the total weight ¹⁰.

Weighing hives

Since the ‘stuff’ in the hive is probably not evenly distributed the weight you record will either be less than or more than half the weight of the hive, depending on whether you have picked the heavy (C in the figure above) or light (D) side of the hive.

However, the sum of the two sides (C + D) will – with the exception of the fraction lost due to vectors as described in the last footnote – still equal the total weight of the hive and contents.

So, if you want to know the total weight either measure the weight of opposing sides and add them together.

Or, measure one side, double it, assume everything is about even and enjoy being a beekeeping free spirit.

You radical 😉

Let the weight stabilise

The solution to the arm-wrenching, patience-draining, interminably-wobbling, weight stabilising problem is to use a lever.

You need two pieces of stout wood, a strong nut and bolt and a few suitably sized washers. One piece of wood forms a vertical support. The second piece of wood is a lever. It is attached near the top of the support using the bolts/washers/nut.

Hive scales

The digital luggage scales are tied to one end of the lever.

You need a way of attaching the hive to the scales. I use a 6 mm roofing bolt.

Now you see it …

All my hive floors are drilled with a 6-7 mm hole through the middle of each side of the floor ¹¹. This is in the side runner of my kewl floors, underneath the OMF and the Varroa tray.

The roofing bolt is pushed fully into this hole and holds everything very securely.

Now you don’t … when pushed fully home the hive is securely attached to the scales

Using this ‘Heath Robinson’ contraption is simplicity itself.

Place the support vertical and adjacent to the hive, attach the scales to the hive floor, gently press down on the other end of the lever and lift the hive no more than 1-2 cm from the hive stand.

Wait a few seconds for the ‘beep’ from the scales, lower the hive gently onto the stand and record double the weight in your hive records.

Or for those of you who are not free spirits but wear a belt and braces with your beesuit, weigh the opposite side of the hive as well, add the weights together and write up your notes 😉

How reproducible is this?

Actually, pretty good 🙂

I did a bunch of measurements on a range of dummy hives of known weights ¹².

By measuring both sides and adding the recorded weights together I determined that the underestimate of the true hive weight was about 8%. With care, the variation in weight of repeated independent measurements of one side of the hive was in the range 0.3 – 1.7%.

That’s more than close enough for me.

You do need to take care to standardise the method you use:

make sure the upright support is vertical
ensure that the pull exerted by the scales is as vertical as possible.
lift the hive by the same distance off the stand. The smaller the distance the more accurately you will determine the total weight ¹³.
push down on the lever gently and smoothly. Don’t jerk the hive. It takes relatively little effort to hold the hive stable for the weight to be recorded ¹⁴

All of which is pretty easy to achieve.

Remember – and this is the last time I’ll write this – these inspections are ”The bees don’t even know they’re being checked” checks ¹⁵. All of the above can be achieved in 1 minute with no disturbance to the colony if you are reasonably careful.

Then what??

Remember, the weight of the hive is not important, it’s whether they have enough stores to rear brood. However, regularly recording the weight as I describe here will allow you to judge how fast the colony is getting through the stores.

Ideally weigh the hive and heft the hive.

You will then more quickly learn to make a judgement based upon hefting along.

Will the colony be underweight – based upon the hive hardware, the weight of the bees, frames and stores – in a week or two when you next visit?

Bees can use their stores fast when they’re unable to forage and rearing brood. Studies by Tom Seeley have demonstrated colony weight reduction in ‘maintenance’ mode was perhaps 1 kg per week, but that this level increased significantly once brood rearing started in earnest.

If you consider that the colony is already too light, or will be too light before your next visit, you must add some stores.

And, at this time of the year you should use fondant, not syrup, to feed bees.

Feeding fondant

I’ve written extensively about feeding fondant to bees, both in midwinter and at the end of the summer. I only use commercial baker’s fondant, not the overpriced stuff sold to ~~gullible~~ wealthy beekeepers.

The priority is to add the fondant as close as possible to the cluster. You want the bees to have immediate access to it. You don’t want them to have to crawl half way across the hive, up through a hole in the crownboard and into that cold empty void under the roof.

Which bees are better able to access the fondant?

Brrrr.

I add fondant in 1 – 5 kg blocks. The amount depends upon the size of the colony, the likely time of my next visit and the probability of their being nectar readily available before then.

I always err on the side of generosity ¹⁶.

You can easily remove unused fondant …

… or you can guiltily remove pathetic handfuls of starved bees.

Your choice 🙁

Pack the fondant into clear plastic food trays ¹⁷ rescued from the recycling bin. Once filled, wrap them with a couple of layers of clingfilm, or place them in a securely sealed plastic bags. The fondant will absorb moisture from the environment, particularly if it’s warm. I just keep a pile of them in the car for my winter visits to the apiary.

Spot the blocks of fondant and the scales

Remove all the clingfilm. Bees have a horrible habit of dragging it down into the brood nest, chewing it up and incorporating it into brace comb.

I place the fondant on top of the frame bars, directly over the cluster. My crownboards are reversible and have a deep upper (i.e lower when reversed!) rim which accommodates the tray of fondant.

Fondant block under an inverted perspex crownboard

I add the insulation block back over the crownboard and replace the roof, secure in the knowledge that the colony has sufficient food for the next 2-3 weeks.

If your crownboards aren’t reversible with a deep rim ~~make some that are~~ use an eke or an empty super.

Science snippets

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Three short and easy-to-digest snippets of science this week. After last weeks’ overly-long DIY extravaganza I thought I’d try and be a little more succinct this time.

The following triptych is based on three separate papers, two published in the last month or two and one from last year. Individually these incremental advances in our understanding probably do not justify a post of their own.

The first paper, on sodium butyrate, was included here following a question I was asked during an evening talk to a beekeeping association last week. I don’t think I answered the question particularly well, so thought I’d elaborate here for clarity. The science is cool, but the paper is rather odd.

The other two papers are on a related topic, the bacteria in the gut of bees. The first of these came out last week and had a very catchy title. Reading that paper resulted in my burrowing back a year or two into the literature. While doing this I found a related paper that has got me thinking again about feeding winter bees honey, syrup or fondant.

Sodium butyrate reverses DWV-induced memory loss

All honey bees, perhaps with the exception of those in Australia ¹, are infected with deformed wing virus (DWV). Historical studies that report 30% or 60% or whatever virus prevalence were probably using an insensitive assay. Even bees in Varroa-free regions carry DWV.

And, in the absence of Varroa, DWV is not a problem to the bee ². It is present at low levels and is apparently not pathogenic.

However, when transmitted by Varroa, the virus levels are amplified about a million times are a range of symptoms are clearly present. These include pupal death or the emergence of workers with overt developmental defects, including the classical ‘does what it says on the tin’ deformed wings.

DWV symptoms

In laboratory studies up to 70% of the bees exposed to high levels of virus exhibit these catastrophic symptoms.

However, some bees emerge with high levels of virus, but ‘look’ normal.

But they don’t behave normally.

In particular they have defects in memory and learning.

Forgetfulness and getting lost

Impairments in memory and learning are bad news for bees.

Foragers need to be able to learn where sources of nectar and pollen are by interpreting the waggle dance. Perhaps more importantly, they need to remember where the hive is so that they can successfully return from a foraging trip. If they forget where they are going, they’re doomed.

A social insect like a honey bee cannot become a solitary bee without inevitably becoming a dead bee.

There is a long history of using sodium butyrate (NaB) to either enhance memory, or to reverse memory loss. It belongs to a class of compounds called HDACi’s (histone deacetylase inhibitors) which have been used in medical studies including anti-neural degeneration and anti-Alzheimer’s disease.

NaB has even been used in studies with honey bees. In these it has been shown to enhance expression of genes involved in the immune response, detoxification and learning/memory.

In addition, NaB restores learning ability in neonicotinoid-treated bees … it was therefore a logical extension (particularly since this neonic study was conducted by the same Taiwanese researchers) to investigate a role for NaB in counteracting DWV-induced learning and memory loss, the topic of the first paper this week ³ .

CCD and ‘massive disappearance’ of bees

This paper is a bit of a curate’s egg. The science is detailed and appears to be done well. The experiments are logical, mostly well-controlled and involve a combination of detailed molecular studies with monitoring bee behaviour in the field.

However, the attempted link between memory loss and bee loss, the association with CCD (colony collapse disorder) and the superlatives in the paper make for a rather strange reading experience.

I’m not going to give a detailed account of the science. The key points are as follows:

NaB increased honey bee survival after oral DWV challenge ⁴. Disappointingly they did no virus assays.
NaB reversed memory loss in the standard proboscis extension assay (PER)
Gene expression studies indicated that NaB (an HDACi) resulted in increased expression of numerous genes, including reversing the suppression of some genes caused by DWV infection. Some of these genes were involved in memory, but many other gene classes were also differentially expressed. NaB was also shown to restore some neurotransmitter activity in the brain.
Colonies fed NaB and then fed DWV experienced a much reduced loss of bees than those that just received DWV.

Sodium butyrate reverses bee loss due to DWV (A) in/out ratios and (B) lost bee ratios

I need to re-read some of the methods and data on the in/out ratios (the graph on the left above) as it appears that more bees returned to the hive than left the hive! These field experiments used an automated hive monitoring system , but did not apparently use any form of tagging on the bees. It is not clear how they could be certain that the ‘returning’ bees originated from the monitored hive.

Smells fishy?

The conclusions of the paper end with the sentence “a diet incorporating histone deacetylase inhibitors could be used to maintain the overall wellbeing of the bees and integrity of the colony”.

Well … perhaps.

I’d argue that prevention is always better than cure.

It is preferable to minimise DWV levels in the hive – by killing Varroa – than it is to try and counteract the deleterious effects of DWV by adding additional chemicals. Studies from my lab and others show that effective Varroa control results in very low virus levels.

But if you are going to feed them HDACi’s, then it probably should not be sodium butyrate.

The ‘butyrate’ bit of the name is derived from butyrum meaning ‘butter’ in Latin. Sodium butyrate is a fatty acid and is famously smelly. It reeks of spoiled milk, or sour butter, and is the compound that gives vomit that distinctive ‘smell-it-a-mile-off’ odour.

Hmmmm …. nice 🙁

So, although it doesn’t smell fishy … it certainly does smell.

Possibly not something you’d want anywhere near hives producing honey 😉

Chicken eating bees

I wrote recently about how important catchy titles are to scientific papers. The title of this next paper was the only thing that made me read the study …

Why Did the Bee Eat the Chicken? Symbiont Gain, Loss, and Retention in the Vulture Bee Microbiome by Figuerosa et al., (2021) mBio 12:e02317-21

How could you not want to read a paper with a title like that?

Well, one reason might be that you don’t know the words symbiont or microbiome.

Let’s see if we can change that … 😉

Vulture bees

Honey bees, along with all other bees, are classified with the sawflies, wasps and ants as members of the Hymenoptera. Of these, bees are wasps that switched to a vegetarian lifestyle, eating pollen and nectar.

Vulture bees dining out on chicken

However, some stingless bees also dine on carrion (literally ‘the decaying flesh of dead animals’) and a few species – the aptly named vulture bees – only feed on carrion for protein and no longer collect pollen.

You are what you eat

The microbiome is a collective term for the all the bacteria ⁵ in a particular environment.

For example, the gut microbiome or the skin microbiome.

In the gut, these microbes help the host exploit novel food resources. For example, honey bees have bacteria (Gilliamella apicola) that help them digest toxic sugars ⁶.

The host (bee) benefits from the presence of the bacteria, and the bacteria benefits from the protection and food provided by the host … which is exactly what the term symbiotic means.

You are what you eat is, of course, not meant literally ⁷.

However, it is certainly true that the symbiotic microbiome is significantly influenced by diet. And the symbiotic microbiome also influences what can be consumed.

The Figuerosa et al., study compared the gut microbiome of a variety of stingless bees from Costa Rica. Some of these bees were pollenivorous and others were facultatively or obligately necrophagous.

Eh?

Pollenivorous – pollen eating
Facultatively – some of the time
Obligately – all of the time / only
Necrophagous – feeding on corpses or carrion

The microbiome of vulture bees

By analysing the microbiome of these different types of bees the authors determined that reversion to a purely necrophagous lifestyle had resulted in the acquisition of a unique range of additional bacterial species.

Gut microbial communities in pollen-eating (absent), or facultatively or obligately necrophagous stingless bees.

However, the gut microbiome was not entirely unique. Many species were also found in facultative necrophagous bees, or in the pollenivorous species.

It’s not yet clear what all these new species actually ‘do’ in the gut of these carrion eating ‘vulture’ bees. Further studies will be needed to determine this.

And, of course, this study begs the additional question.

Which came first, the chicken or the bacteria? ⁸

Did the microbiome change in response to a change in diet, or was the change in diet enabled by the change in the microbiome?

And, the topic of changes in the microbiome is the topic of the third paper … which, you’ll be relieved, is on honey bees.

The microbiome of summer and winter bees

I really used the ‘vulture bees’ paper to introduce the concept of the symbiotic microbiome.

In honey bees, the microbiome has been extensively studied over the last decade or so.

A striking feature is that it includes relatively few species of bacteria, and is dominated by less than 10 in total ⁹. These species are conserved regardless of geography, life stage (nurse bee, forager etc.) or season.

Almost every study of the honey bee microbiome has been a qualitative one. By that I mean the scientists determine the species present, but ignored the quantities of the different bacteria.

In comparison, a quantitative study would have determined the amounts of some or all of the core species in the microbiome.

And that is exactly what Kešnerová et al., (2020) did in their study entitled Gut microbiota structure differs between honeybees in winter and summer ¹⁰.

Multi-year, multi-hive studies

As you would expect from a paper in the ISME Journal ¹¹ this is a thorough study, involving sampling of one hive on a monthly basis for 24 months, and fourteen hives in two different locations in the summer and winter. Each sampling involved multiple individual bees that were analysed. There are some additional experiments on colonisation of the gut that I’m going to largely ignore here.

The authors qualitatively and quantitatively studied only five of the core species and two non-core species from the gut microbiome. The names don’t really matter, but are shown in the figures below.

The gut microbial community differs between summer foragers and winter bees

There’s a huge amount of date in this figure.

However, simply by looking at the monthly changes (A), or the community composition (B), it is clear that summer foragers and winter bees have significantly different microbial populations within the gut.

In addition, the overall levels of many of the species tested (C) were significantly increased in the winter bees population.

Summer bees, nurse bees and winter bees

From a physiological and dietary point of view, there are some similarities between nurse bees and the long-lived winter bees. The authors therefore tested the bacterial population the gut of each contained in summer (foragers and nurse bees) and winter (winter bees).

Bacterial load and community composition in foragers, nurse and winter bees

Nurse bees and winter bees contained at least 10 times the population of bacteria as present in the gut of foragers (A, above). Of these, nurse bees were intermediate in the range of species between the foragers – which had a greater range – and the winter bees which contained fewer species.

Finally, detailed statistical analysis of the populations in the three bee types indicated that they were distinct (C), despite conservation of several of the core microbiome species. This latter analysis showed that, whilst each was distinct, all of the populations were similarly variable within a particular bee type i.e. none of the dots are more clustered/scattered in the third panel above.

Diet and the microbiome

Numerous studies have shown that diet influences the bacteria in the gut – of honey bees, vulture bees, flies, mice and men. It’s therefore very likely that the diet of nurse and winter bees at least partly accounts for the differences in the bacterial community present in their gut.

Foragers need an energy-rich diet and mainly feed on nectar and honey. In contrast, nurse bees and winter bees also consume pollen.

In studies I don’t have time to discuss, Kešnerová et al., (2020) also showed that feeding gnotobiotic bees ¹² pollen and syrup resulted in significant increases in the amount and levels of bacterial colonisation i.e. they resembled nurse or winter bees. In contrast, bees fed syrup alone developed a gut microbiota that resembled that of foragers.

All of which made me think about feeding bees syrup/fondant for the winter vs. feeding/leaving them honey.

Honey is better for bees in the winter … really?

Beekeepers who leave their bees with a super or so of honey are often convinced of the benefits to the colony.

When pressed they unfortunately provide little evidence to support their expensive decision ¹³.

I’m not aware of a single study that convincingly i.e. statistically, demonstrates that colonies are more successfully overwintered on a diet of pure honey, rather than a colony fed syrup or fondant.

I’ve discussed this before – for example, see my response to this comment in the post entitled ‘Cut more losses’.

Is the microbiome a marker of colony health?

However, this paper on the winter bee microbiome got me wondering whether – in the absence of evidence supporting better overwintering survival – bees fed syrup/fondant or honey have a different bacterial population.

It would be very interesting if they did.

Furthermore, as scientists further untangle the role of these bacteria, we would be able to tell whether syrup/fondant was better, worse or neutral in terms of the changes it induced in the bacteria that inhabit the winter bee gut.

Unfortunately, the Kešnerová et al., (2020) study has no details whatsoever of the hive management regime. The work was done in Lausanne, Switzerland, but it doesn’t say how or what they were fed for the winter.

Nor is there any mention of whether the diet was supplemented with sodium butyrate ¹⁴. This will also need to be studied as butyrate is a natural product of some gut microbes and there is evidence that – in humans at least – it is involved in communication between the gut and the brain.

And I think my gut is telling my brain that it would like some pizza …

Hydroxymethylfurfural

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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.

Dysentery

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 …

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)

Fondant

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?

Note

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

Introduction

And gathering swallows twitter in the skies

Supers

Storing supers wet or dry?

Feeding fondant

Apivar-contaminated honey and supers

But what to do with the now-empty-but-Apivar-exposed supers?

Final inspections

Queenright?

Look and ye shall find …

Stores

Disease

Closing up

Goodbye and thanks for the memories

Introduction

Painting and decorating

Entrances and exits

Crownboards

Feeder mods

Frames

Judging queen quality

Queen introduction

Rear some spares

Keeping things going

Scrub ‘caretaker’ queens

The end of the queen rearing season

Overwintering mini-nucs

Gimme shelter

Finally

References

Introduction

Avoirdupois 1

Silent spring

Winter weight

Hefting the hive

Weighing the hive

Physics … Ewwww!

Let the weight stabilise

How reproducible is this?

Then what??

Feeding fondant

Sodium butyrate reverses DWV-induced memory loss

Forgetfulness and getting lost

CCD and ‘massive disappearance’ of bees

Smells fishy?

Chicken eating bees

Vulture bees

You are what you eat

The microbiome of vulture bees

The microbiome of summer and winter bees

Multi-year, multi-hive studies

Summer bees, nurse bees and winter bees

Diet and the microbiome

Honey is better for bees in the winter … really?

Is the microbiome a marker of colony health?

Natural occurrence of HMF

HMF in honey

How to avoid the generation of HMF in honey

Quantifying HMF

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

Further validation of the adverse effects of HMF to adult bees

Dysentery

Real world beekeeping

Oxalic acid

Fondant

On the internet, nobody knows you’re a dog

Note

Avoirdupois ¹