Tag Archives: broodless

Broodless?

Synopsis : The colony needs to be broodless for effective oxalic acid treatment in winter. You might be surprised at how early in the winter this broodless period can be (if there is one). How can you easily determine whether the colony is broodless?

Introduction

In late spring or early summer a broodless colony is a cause for concern. Has the colony swarmed? Have you killed the queen? Since worker brood takes 21 days from egg to emergence, a broodless colony has gone 3 weeks without any eggs being laid.

You’re right to be concerned about the queen.

Of course, since you’ve been inspecting the hive on a 7-10 day rotation, you noticed the absence of eggs a fortnight ago, so you’re well on your way to knowing what the problem is, and therefore being able to solve it 😉 .

But in late autumn or early winter a broodless colony is not a cause for concern.

It’s an opportunity.

Are they rearing brood? Probably by now … it’s mid-January

In my view it’s a highly desirable state for the colony to be in.

If the colony is broodless then the ectoparasitic Varroa mites cannot be hiding away under the cappings, gorging themselves on developing pupae and indulging in their – frankly repellent – incestuous reproduction.

Urgh!

Instead the mites will all be riding around the colony on relatively young workers (and in winter, physiologically all the workers in the hive are ‘young’, irrespective of their age) in what is incorrectly termed the phoretic stage of their life cycle.

This is incorrect as phoresy means “carried on the body of another organism without being parasitic” … and these mites are not just being carried around, they’re also feeding on the worker bees.

You can read all about phoretic mites, their diet and their repulsive reproductive habits in previous posts.

What is the opportunity?

A broodless colony in the winter is an opportunity because phoretic mites (whether misnamed or not) are very easy to kill because they’re not protected by the wax capping covering the sealed brood.

Total mite numbers surviving OA treatment depends upon the proportion in capped cells

And today’s post is all about identifying when the colony is broodless.

Discard your calendar

I’ve said it before 1 … the activities of the colony (swarming, nectar gathering, broodlessness 2 ) are not determined by the calendar.

Instead they’re determined by the environment. This covers everything from the available forage to the climate and recent weather 3.

And the environment changes. It changes from year to year in a single location – an early spring, a late summer – and it differs between locations on the same calendar date.

All of which means that, although you can develop a pretty good idea of when you need to intervene or manage things – like adding supers, or conducting swarm control – these are reactive responses to the state of the colony, rather than proactive actions applied because it’s the 9th of May 4.

And exactly the same thing applies to determining when the colony is broodless in the winter. Over the last 6 years I’ve had colonies that are broodless sometime between between mid October and mid/late December. They’re not broodless for this entire period, but they are for some weeks starting from about mid-October and ending sometime around Christmas.

Actually, to be a little more precise, I generally know when they start to be broodless, but I rarely monitor when they stop being broodless, not least because it’s a more difficult thing to determine (as will become clear).

Don’t wait until Christmas

A broodless colony is an opportunity because the phoretic mites can easily be killed by a single application of oxalic acid.

Many beekeepers treat their colonies with oxalic acid between Christmas and New Year.

It was how they were taught when they started beekeeping, it’s convenient because it’s a holiday period, it’s a great excuse to escape to the apiary and avoid another bellyful of cold cuts followed by mince pies (or the inlaws 5 ) and because it’s ‘midwinter’.

But, my experience suggests this is generally too late in the year.  The colony is often already rearing brood by the time you’ve eaten your first dozen mince pies.

If you’re going to go to the trouble of treating your colonies with oxalic acid, it’s worth making the effort to apply it to achieve maximum efficacy 6.

I’m probably treating my colonies with oxalic acid in 8-9 days time. The queens have stopped laying and there was very little sealed brood present in the colonies I briefly checked on Monday this week. The sealed brood will have all emerged by the end of next week.

It’s worth making plans now to determine when your colonies are broodless. Don’t just assume sometime between Christmas and New Year ’will be OK’.

But it’s too early now for them to be broodless … or to treat with oxalic acid

If your colonies are going to go through a broodless period this winter 7 it’s more likely to be earlier rather than later.

Why?

Because if the colonies had a long broodless period stretching into mid-January or later it’s unlikely they’ll build up strongly enough to swarm … and since swarming is honey bee reproduction, it’s a powerful evolutionary and selective pressure.

Colonies that start rearing brood early, perhaps as early as the winter solstice, are more likely to build up strongly, and therefore are more likely to swarm, so propagating the genes for early brood rearing.

But surely it would be better to treat with oxalic acid towards the end of the winter?

Mites do not reproduce during the misnamed phoretic stage of the life cycle. Therefore, aside from those mites lost (hopefully through the open mesh floor) due to allogrooming, or that just die 8, there will be no more mites later in the broodless period than at the beginning.

Since the mites are going to be feeding on adult workers (which is probably detrimental to those workers), and because it’s easier to detect the onset of broodlessness (see below), it makes sense to treat earlier rather than later.

Your bees will thank you for it 😉 .

How to detect the absence of brood

Tricky … how do you detect if something is not present?

I think the only way you can be certain is to conduct a full hive inspection, checking each side of every frame for the presence of sealed brood.

Perhaps not the ideal conditions for a full hive inspection

But I’m not suggesting you do that.

It’s a highly intrusive thing to do to a colony in the winter. It involves cracking open the propolis seal to the crownboard, prising apart the frames and splitting up the winter cluster.

On a warm winter day that’s a disruptive process and the bees will show their appreciation 🙁 . On a cold winter day, particularly if you’re a bit slow checking the frames (remember, the bees will appear semi-torpid and will be tightly packed around any sealed brood present, making it difficult to see), it could threaten the survival of the colony.

And don’t even think about doing it if it’s snowing 🙁 .

Even after reassembling the hive the colony is likely to suffer … the broken propolis seals will let in draughts, the colony will have to use valuable energy to reposition themselves.

A quick peek

I have looked in colonies for brood in the winter. However, I don’t routinely do this.

Now, in mid/late autumn the temperature is a bit warmer and it’s less disruptive. I checked half a dozen on Sunday/Monday. It was about 11°C with rain threatening. I had to open the boxes to retrieve the Apivar strips anyway after the 9-10 week treatment period.

Recovered Apivar strips

I had repositioned the Apivar strips about a month ago, moving them in from the outside frames to the edges of the shrinking brood nest. By then – early October – most of the strips were separated by just 3 or 4 frames.

The flanking frames were all jam packed with stores. The fondant blocks were long-gone and the bees had probably also supplemented the stores with some nectar from the ivy.

Over the last month the brood nest continued to shrink, but it won’t have moved somewhere else in the hive … it will still be somewhere between the Apivar strips, and about half way is as good a place as any to start.

Apivar strip (red bars) placement and the shrinking brood nest

So, having removed the crownboard and the dummy board, I just prise apart the frames to release the Apivar strips and then quickly look at the central frame between them. If there’s no sealed brood there, and you can usually also have a look at the inner faces of the flanking frames down the ‘gap’ you’ve opened, then the colony is probably broodless.

It takes 45-60 seconds at most.

It’s worth noting that my diagram shows the broodnest located centrally in the hive. It usually isn’t. It’s often closer to the hive entrance and/or (in poly boxes) near the well insulated sidewall of the hive.

Hive debris

But you don’t need to go rummaging through the brood box to determine whether the colony is broodless (though – as noted earlier – it is the probably the only was you can be certain there’s no brood present).

The cappings on sealed brood are usually described as being ‘biscuit-coloured’.

Not this colour of biscuit

‘Biscuit-coloured’ is used because all beekeepers are very familiar with digestive biscuits (usually consumed in draughty church halls). If ‘biscuit-coloured’ made you instead think of Fox’s Party Rings then either your beekeeping association has too much money, or you have young children.

Sorry to disappoint you … think ‘digestives’ 😉 .

That’s more like it …

The cappings are that colour because the bees mix wax and pollen to make them air-permeable. If they weren’t the developing pupa wouldn’t be able to breathe.

And when the developed worker emerges from the cell the wax capping is nibbled away and the ‘crumbs’ (more biscuity references) drop down through the cluster to eventually land on the hive floor.

Where they’re totally invisible to the beekeeper 🙁 .

Unless it’s an open mesh floor … in which case the crumbs drop through the mesh to land on the ground where they’ll soon get lost in the grass, carried off by ants or blown away 🙁 .

It should therefore be obvious that if you want detect the presence of brood emerging you need to have a clean tray underneath the open mesh floor (OMF).

Open mesh floors and Correx boards

Most open mesh floors have a provision to insert a Correx (or similar) board underneath the mesh. There are good and bad implementations of this.

Poor designs have a large gap between the mesh and the Correx board, with no sealing around the edges 9. Consequently, it’s draughty and stuff that lands on the board gets blown about (or even blown away).

Good designs – like the outstanding cedar floors Pete Little used to make – have a close-fitting wooden tray on which the Correx board is placed. The tray slides underneath the open mesh floor and seals the area from draughts 10.

Open mesh floor and close-fitting Varroa tray by Pete Little

Not only does this mean that the biscuity-coloured crumbs stay where they fall, it also means that this type of floor is perfect when treating the colony with vaporised oxalic acid. Almost none escapes, meaning less chance of being exposed to the unpleasant vapours if you’re the beekeeper, and more chance of being exposed to the unpleasant vapours if you’re a mite 😉 .

Since the primary purpose of these Correx trays is to determine the numbers of mites that drop from the colony, either naturally or during treatment, it makes sense if they are pale coloured. It’s also helpful if they are gridded as this makes counting mites easier.

Easy counting ...

Easy counting …

And, with a tray in situ for a 2-3 days you can quickly get an idea whether there is brood being uncapped.

Reading the runes

The diagram below shows a schematic of the colony (top row) and the general appearance of debris on the Varroa tray (bottom row).

It’s all rather stylised.

The brood nest – the grey central circle is unlikely to be circular, or central 11.

The shrinking broodnest (top) and the resulting pattern on the Varroa tray (bottom)

Imagine that the lower row of images represent the pattern of the cappings that have fallen onto the tray over at least 2-3 days.

Biscuit-coloured cappings on Varroa tray

As the brood nest shrinks, the area covered by the biscuit-coloured cappings is reduced. At some point it is probably little more than one rather short stripe, indicating small amounts of brood emerging on two facing frames.

With just one observation highlighted should you plan to treat next week?

Let’s assume you place the tray under the open mesh floor and see that single, short bar of biscuity crumbs (highlighted above). There’s almost nothing there.

Do you assume that it will be OK to treat them with oxalic acid the following week?

Not so fast!

With just a single observation there’s a danger that you could be seeing the first brood emerging when there’s lots more still capped on adjacent frames.

It’s unlikely – particularly in winter – but it is a possibility.

Far better is to make a series of observations and record the trajectory of cappings production. Is it decreasing or is it increasing?

Multiple observations allows the expanding or contracting brood nest to be monitored

With a couple of observations 10-12 days apart you’ll have a much better idea of whether the brood area is decreasing over time, or increasing. Repeated observations every 10-12 days will give you a much better idea of what’s going on.

Developing brood is sealed for ~12 days. Therefore, if brood rearing is starting, the first cappings that appear on the Varroa tray are only a small proportion of the total sealed brood in the colony.

Very little cappings but certainly not broodless

Of course, in winter, the laying rate of the queen is much reduced. Let’s assume she’s steadily laying just 50 eggs per day i.e. about 12.5 cm2. By the time the first cappings appear on the Varroa tray (as the first 50 workers emerge) there will be another 600 developing workers occupying capped cells … and the worry is that they’re occupying those cells with a Varroa mite.

The cessation of brood rearing

In contrast, if there’s brood in the colony but the queen is slowing down and eventually stops egg laying, with repeated observations 12 the amount and coverage of the biscuit-coloured cappings will reduce and eventually disappear.

At that point you can be reasonably confident that there is no more sealed brood in the colony and, therefore, that it’s an appropriate time to treat with oxalic acid.

In this instance – and unusually – absence of evidence is evidence of absence 🙂 .

But my bees are never broodless in the winter

All of the above still applies, with the caveat that rather than looking for the absence of any yummy-looking biscuity crumbs on the tray, you are instead looking for the time that they cover the minimal area.

If the colony is never broodless in winter it still makes sense to treat with oxalic acid when the brood is at the lowest level (refer back to the first graph in this post).

At that time the smallest number of mites are likely to be occupying capped cells.

However, this assumption is incorrect if the small number of cells are very heavily parasitised, with multiple mites occupying a single sealed cell. This can happen – at least in summer – in heavily mite infested hives. I’ve seen 12-16 mites in some cells and Vincent Poulin reported seeing 26 in one cell in a recent comment.

Urgh! (again)

I’m not aware of any data on infestation levels of cells in winter when brood levels are low, though I suspect this type of multiple occupancy is unlikely to occur (assuming viable mite numbers are correspondingly low). I’d be delighted if any readers have measured mites per cell in the winter, or know of a publication in which it’s reported 13.

This isn’t an exact science

What I’ve described above sounds all rather clinical and precise.

It isn’t.

Draughts blow the cappings about on the tray. The queen’s egg laying varies from day to day, and can stop and start in response to low temperatures or goodness-knows-what-else. The pattern of cappings is sometimes rather difficult to discern. Some uncapped stores can have confoundingly dark cappings etc.

But it is worth trying to work out what’s going on in the box to maximise the chances that the winter oxalic acid treatment is applied at the time when it will have the greatest effect on the mite population.

By minimising your mite levels in winter you’re giving your bees the very best start to the season ahead.

Unrestricted mite replication – the more you start with the more you end up with (click image for more details)

The fewer mites you have at the start of the season, the longer it takes for dangerously high mite levels (i.e. over 1000 according to the National Bee Unit) to develop. Therefore, by reducing your mite levels in the next few weeks you are increasing your chances that the colony will be able to rear large numbers of healthy winter bees for next winter.

That sounds to me like a good return on the effort of making a few trips to the apiary in November and early December …


 

OA Q&A

The post last week on the preparation of oxalic acid (OA; the active ingredient in the commercially available and VMD approved product Api-Bioxal) generated a slew questions. Inevitably, some of these drifted off topic … at least as far as the specific content of the post was concerned.

This partly reflects the deficiency of a weekly blog as a means of communicating.

It may also reflect the inadequacy of the indexing system 1.

Comprehensive coverage of subject, and peripherally related topics, would require a post so long that most readers 2 would give up halfway through.

And it would take so long to write that the weekly post format would have to be abandoned.

The resulting magnum opus would be a masterpiece of bad punctuation, littered with poor puns and would leave me nothing to write the following week …

This week I’ve attempted to address a series of oxalic acid-related points that should have been mentioned before, that I’ve received questions about, or I think justify a question (and answer).

Should I trickle treat or vaporise?

One of the key features of approved miticides is that, used according to the instructions and at the appropriate time, they are very effective.

Conversely, use them incorrectly or at the wrong time and they will be, at best, pretty hopeless.

In the case of OA, both trickle treating (dribbling) or vaporisation (sublimation) can achieve 90% or more reduction in the levels of phoretic mites.

Therefore, the choice between them is not on the grounds of efficacy but should be on their ease of us, convenience, safety or other factors.

Trickle treating is fast, requires a minimum amount of specialised equipment and only limited PPE (personal protection equipment).

I’d strongly recommend using a Trickle 2 bottle from Thorne’s to administer the solution. It is infinitely better than a syringe, which requires the use of at least two hands.

If you hold the crownboard up at an angle with one hand you can administer the OA solution using the other. Wear gloves and your bee suit. It takes as long to read as it does to do.

With a Trickle 2 bottle and some pre-warmed OA-containing solution it should be possible to open, treat and close a colony in well under two minutes. Like this …

On a cold day very few bees will be disturbed. The OA will dribble down through the clustered colony and the mites will get what they deserve 🙂

Temperature and treatment choice

It’s usually the temperature that determines whether I trickle or vaporise. I prefer to trickle when the colony is clustered, but would usually treat by sublimation on a warmer day.

At what temperature does cold become warm? About 8-9°C … i.e. about the temperature at which the bees start to cluster.

Partly this is to reduce the number of bees that might be disturbed – I can vaporise a colony without opening the box.

However, my crashingly unscientific opinion – based entirely on gut feeling and guesswork 3 – is that the OA vapour perfuses through loose clusters  better, whereas the solution is more likely to come into contact with the mites when dribbling down through the cluster.

I have no data to support this – don’t say you weren’t warned!

Through choice I’d not treat (unless I had to) if the temperature was much below 3-4°C. The bees get rapidly chilled should something goes wrong – you drop the bottle, get a bee in your veil or whatever.

Single use ...

Caramel coated Sublimox vaporiser pan

Of course, if you haven’t got a vaporiser your choice is limited to trickle treating. Likewise, if you don’t enjoy scouring caramelised glucose from the pan of your vaporiser you should probably stick to trickling Api-Bioxal solution.

The only additional thing to consider is whether there’s brood present in the hive – I discuss this in more detail below.

How can I use a vaporiser and an Abelo poly floor?

I use a lot of Abelo poly hives. Mine are all the ‘old design‘ with the floor that features a long landing board and an ill-fitting Varroa tray. The new ones don’t look fundamentally different from the website 4.

Abelo poly National hives ...

Abelo poly National hives …

My storage shed has a shoulder-high stack of unused Abelo floors as I prefer my own homemade ‘kewl’ floors.

However, inevitably some Abelo floors get pressed into use during the season and – through idleness, disorganisation and a global virus pandemic – remain in use during the winter 🙁

I’ve now worked out how to vaporise colonies using these floors. Please remember, my vaporiser is a Sublimox which has a brass (?) nozzle through which the vapour is expelled. The nozzle gets very hot and melts polystyrene.

Don’t ask me how I know 🙁

The underside of the open mesh floor can be sealed by inverting the Varroa tray and wedging a block of foam underneath at the back. I didn’t think this would work until I tried it, and was pleasantly impressed.

Abelo poly floor set up for OA vaporisation

This is important as it significantly reduces the loss of OA vapour. Any vapour that escapes is OA that will not be killing mites.

The Sublimox can be simultaneously inserted and inverted through the front entrance. This takes some deft ‘wrist action’ but results in minimal loss of OA vapour.

To protect the poly I use a piece of cardboard. You simply rest the nozzle on this.

As soon as the vaporiser is removed the bees will start to come out, so use the cardboard to block the entrance for a few minutes, by which time they will have settled.

No expense spared cardboard ‘protector’ for poly floor

The gaffer tape in the photo above is sealing the ventilation holes in the entrance block, again keeping valuable OA vapour inside the hive.

And on a related point …

My favoured nuc is the Everynuc. This is a Langstroth-sized box with a removable floor and an integral feeder that more-or-less converts the box to take National frames. It’s well-insulated, robust, easy to paint and – in my view – a more flexible design that the all-in-one single moulded boxes (like the offering from Maisemores).

However, the entrance of the Everynuc is too big.

Everynuc entrance

Open wide …

The disadvantage of this is that a DIY entrance reducer is needed if the nuc is weak and at risk from robbing.

Conversely, the large entrance and short (~2cm) “landing board” is preferable during OA vaporisation. I carry a nuc-width strip of wood, 2 cm thick, with a central 7 mm hole.

With this balanced on the landing board, the vaporiser can be inserted and inverted without loss of vapour or risk of melting the poly. It’s a quick and dirty fix that I discovered several years ago and have never got round to improving.

How do I know if the colony is broodless?

Oxalic acid is a single-use treatment, remaining active in the hive for significantly less time than a brood cycle (see mite counts below). Therefore, the ‘appropriate time’ to use it is when the colony is broodless.

An additional consideration is that open brood is very sensitive and responds unfavourably to a warm acid bath in OA i.e. it dies 5.

In contrast, sealed brood is impervious to OA vapour or solution.

So, how can you tell if the colony is broodless or not?

The easiest way to determine whether the colony has sealed brood is – on a slightly better day – to open the box and have a look.

Done quickly and calmly I suspect this is more distressing for the beekeeper than it is for the colony. You think the bees will be aggressive or distressed. In reality they’re usually pretty lethargic and often very few fly at all.

You only need to look at the frame in the centre of the cluster. If there’s brood present it will be where the bees are most concentrated. You will probably well see the queen nearby.

Gently, gently, quicky peeky

Remove the roof and insulation and lift one corner of the crownboard. Give them a gentle puff of smoke under the crownboard 6. Wait 30 seconds or so and gently remove the crownboard.

There will be bees on the underside of the crownboard. Stand it carefully to the side out of the breeze. The bees will probably crawl to the upper edge, remember to shake them off into the hive rather than crush them when you place it back on the hive.

The colony is likely to be clustered if the weather is 8°C or cooler. Remove the outer frame furthest from the cluster. If it’s late autumn or early winter this should still be heavy with stores. Here’s one I pulled out last week.

Outer frame from a colony in early winter

Now you have space to work. Viewed from above the cluster will often be spread over several frames and shaped approximately like a rugby ball.

In the hive shown above they occupied the front five seams 7 with a few stragglers between frames 6 and 7.

Early winter cluster

I used my hive tool between frames 3 and 4 to split the colony, just levering them a centimetre or so apart, so I could then separate frame 3 from 2 and lift it out.

The queen was on the far side of frame 3.

It looks like magic to inexperienced beekeepers, but it really isn’t …

The top of the frame was filled with sealed stores, the lower part of the frame was almost full of uncapped stores.

There was no sealed brood and no eggs or larvae that I could see 8. An adjacent hive looked very similar. Again, the queen was on the reverse side of the first frame I checked. The bees were barely disturbed. Almost none flew and the boxes were carefully sealed up again.

No brood, so ready to treat 🙂

Can I determine if there’s brood present without opening the hive?

Possibly.

You should be able to tell if brood is emerging by the appearance of the characteristic biscuit-coloured wax crumbs on the Varroa tray.

Think digestive rather than Fox’s Party Rings

Not this colour of biscuit

To see this evidence you need to start with a clean Varroa tray. In addition, the underside of the open mesh floor must be sufficiently draught-free that the cappings aren’t blown around, or accessible to slugs.

Cleaned Varroa tray

Remember that there might be only a very small amount of brood emerging. They may also be uncapping stores (which will have much paler cappings).

Leave the tray in place for a few days and check for darker stripes of crumbs/cappings under the centre of the cluster.

Biscuit-coloured cappings on Varroa tray

Note that the photograph above was taken in mid-February. A late autumn colony would almost certainly have significantly less brood cappings present on the tray. The brood cappings are the two and a bit distinct horizontal stripes concentrated just above centre. The stores cappings are the white crumbs forming the just discernible stripes the full width of the tray.

You cannot use this method to infer anything about whether there’s unsealed brood present. At least, not with any certainty. If, in successive weeks, the amount of brood cappings increases there’s almost certainly unsealed brood present. Conversely, if brood cappings are reducing there may not be unsealed brood if the queen is just shutting down.

While you’re staring at the tray …

Look for Varroa.

It’s useful to have an idea of the mite drop in the few days before OA treatment.

If it’s high then treatment is clearly needed.

If it’s low (1-2 per day) you have a useful baseline to compare the number that fall after treatment.

You may well be surprised (or perhaps disappointed) at the number that appear from a colony that has already had an autumn treatment.

It’s worth remembering that 9 there will be more mites present in the winter if you treated early enough in the autumn to protect the winter bees (blue line).

Mite numbers after early and late autumn treatment

Conversely, if you get little or no mite drop with an OA treatment in the winter it indicates the  bees have not been rearing brood in the intervening period. That means the diutinus winter bees were reared before or during the last treatment, meaning they will have been exposed to high mite levels (red line).

This is not a good thing™.

In my experience the daily mite drop is highest 24-48 hours after treatment. I usually try and monitor it over 5-7 days by which time the drop has reached a basal level, presumably because the OA has disappeared or stopped being effective.

Finally, the ambient temperature has an influence on the Varroa drop. I’ll write about this sometime in the future, but it’s worth looking out for.


 

Weather to treat

Not Whether to treat? … to which the answer is yes. Instead, a poor pun on the choice of how I use temperature as an indication of when to treat colonies in midwinter …

Midwinter OA-based treatments

Oxalic acid-based treatments for midwinter Varroa control are most effective when colonies are broodless. This is because oxalic acid (OA) treatments only kill phoretic mites and are ineffective against mites in sealed cells. They are therefore ideal for use on swarms, packages and broodless colonies in midwinter.

Winter in the apiary

These OA treatments include Api-Bioxal, the VMD-approved treatment, and unmodified oxalic acid, it’s active ingredient. The importance of midwinter treatments, the preparation of the OA solution and how to trickle treat have recently been covered. I’ve previously discussed sublimation and will do so again in a longer article in the future.

The beekeepers winter dilemma

How can you tell whether your colonies are broodless in midwinter?

On a warm, sunny, Spring afternoon this takes just a couple of minutes … remove the roof, crack off the crownboard, gently lift out the dummy board and the adjacent frame, look carefully at the mass of bees covering the top bars, aim for about the middle and gently prise apart those two frames, lift out a frame from one side of the ‘gap’ and – Hey presto – brood.

Just writing that in early December makes me hanker for much warmer days …

Memories of midseason

Memories of midseason

Actually, you can do exactly the same in midwinter. There are videos on the internet showing an experienced and (in)famous Finnish beekeeper opening his colonies at -10ºC.

I’ve opened and briefly inspected colonies at low temperatures (though not sub-zero). The bees are usually pretty torpid, reluctant to fly – or simply too cold to – and you can be in and out in just a minute or so. Bees cope pretty well with this. It undoubtedly disturbs them a bit and it breaks the propolis seal on the crownboard, but – done carefully and quickly – it’s the only foolproof way to determine whether a colony is broodless in midwinter.

But what if they’ve got brood and it’s therefore not the optimal time to treat? Do you go back and repeat the entire process in 1-2 weeks? What if it’s snowing next time, or there’s a howling gale blowing?

An alternative approach is needed.

The annual brood rearing cycle

As the colony moves from summer to autumn the egg laying rate of the queen drops. It goes on dropping, although not necessarily smoothly, as the days shorten further, the temperature drops and the sources of pollen and nectar disappear. If the queen stops laying altogether then the colony will become broodless about 21 days later.

At some point, perhaps early in the New Year, the queen starts laying again. Slowly at first, but at increasing levels as the season starts. Once foraging starts in earnest the egg laying rate increases markedly and peaks sometime in June.

The precise timing of all these changes cannot be predicted. It’s likely to be dependent on a range of factors – nectar and pollen availability, the strain of bee, day length (and whether it’s increasing or decreasing) and temperature.

Of these, temperature probably has the greatest influence.

Probablyß.

Generalised annual brood and worker numbers ...

Generalised annual brood and worker numbers …

Here’s a quick’n’dirty graph put together with BEEHAVE showing a generalised annual cycle of total brood (blue) and adult bee (red) numbers. Under the conditions in this model the colony is broodless for ~30 days at the end if the year.

Temperate(ure)

Part of the problem with being definitive about the annual brood cycle is the temperature variation with latitude. Temperate regions stretch – in Europe – from Northern Finland to Southern Spain. Bees are kept throughout this range, but obviously experience wildly different climates.

And then there’s the year to year variation.

So if you can’t predict when the colony is going to be broodless, perhaps you can observe the weather – and in particular the temperature – and make an educated guess.

Watch the weather

Over the last few years I’ve applied my midwinter treatment soon (<6 days) after the end of the first extended cold period of the season. This is generally earlier than most beekeepers, who often treat between Christmas and New Year, or early in January.

So, how do we reasonably accurately monitor the weather for a suitable time to treat?

Ho ho ho

Ho ho ho

Most of us live in centrally-heated splendour, protected from the day-to-variation of temperature by heated car seats, air conditioning, hot water bottles, Thinsulate and wood-burning stoves. Do you know what the temperature was today? Rather than trust the wildly-variable (in accuracy) national weather reports for the actual temperature near my apiaries, I instead use very much more local data from Weather Underground.

There are hundreds of ‘amateur’ weather stations across the country that upload data to wunderground.com. Most of these provide current and historic data, including temperature (max, min and average). Here’s one for Auchtermuchty in Fife (on wunderground.com) and directly from the weather station.

Once the weather cools I keep an eye on the average temperature over an extended period of a fortnight or so. If it remains low I wait a bit more … but I then treat as soon as practical after it warms up to 8-10°C or so.

The proof of the pudding

Here’s a graph of the temperature data for 2016§. As indicated on the graph, I treated colonies on the 7th of December.

2016 temperature data and OA treatment ...

2016 temperature data and OA treatment …

I didn’t open my colonies, but others opened on the same day nearby were all broodless. The 7th was chosen as it was the first warm (relatively!) day after a 19 day window in which the average temperature had barely climbed above 5°C.

These treated colonies went into the New Year with vanishingly low Varroa levels.

And again …

This year appears to be repeating a very similar pattern. We’ve had frosts most nights since the 10th of November. It started to warm up significantly in early December as storm Caroline bore down on Scotland and I treated most of my colonies on the 6th 

… by the light of a head torch, in light rain and strengthening wing at 7pm after work.

No, I didn’t open any of the hives to check if they were broodless  😉

It was over 11°C in the apiary when I treated, the barometer was plummeting and the forecast was for near-zero temperatures within 24 hours and remaining that way for another 10 days.

Some of my hives have perspex crownboards. These allow me to check both the state of the colony and if the vapour from my Sublimox has permeated to every corner of the hive. All the colonies were very loosely clustered, with a few bees even wandering out briefly onto the landing board in the dark as I bumbled around preparing things.

The Varroa trays will now be checked in a week or so to work out the mite infestation levels. In the meantime, I can start planning for the coming season knowing I’ve done the best I can to reduce virus levels in the colonies, so giving them a good start to the year.

A Hi tech solution?

Colonies rearing brood maintain a higher, and stable, broodnest temperature (32-35°C) than colonies without brood. It is therefore possible to determine whether a colony has brood by monitoring the temperature directly, rather than trying to infer it from the ambient temperature.

Brood rearing starts ...

Brood rearing starts …

Arnia make hive monitors that allow this sort of thing to be measured. It would be interesting to relate the brood temperature to the ambient temperature (described above) to determine how accurate or otherwise simply ‘watching the weather’ is. Of course … what you’d really want to do is monitor when brood rearing stops and treat soon after that.

Stop press

I treated colonies in our research apiary the following day – the 7th – with dribbled Api-Bioxal. The temperature had dropped almost 7°C since the previous evening and colonies were again beginning to cluster tightly. Under these conditions I’m never confident that the OA vapour penetrates fully, so prefer to trickle treat.

I briefly checked one strong colony in a poly hive for brood.

It was broodless, as I’d hoped  🙂

Of course, this doesn’t guarantee all the others are also broodless, but it does give me some confidence that I’d chosen the correct weather to treat.


† This article, like most on this site, discuss beekeeping issues relevant to temperate climates. It’s important to make this clear now as most of what follows is irrelevant to readers from warmer regions.

∞ Even if there is brood in midwinter, it’s going to be in pretty small amounts. The rate at which this brood emerges is going to be low. The chances of determining what’s going in the colony by ‘reading the tea leaves’ from the debris falling through the mesh floor of the hive is therefore not great. It would probably also require repeated visits to the apiary.

ß This needs qualifying … in midseason, when the temperature varies but it’s not generally cold, the nectar flow is probably the rate-limiting step for brood rearing. The June gap is regularly associated with the queen shutting up shop for a while. However, in late autumn and early winter I’m sure the plummeting temperatures is a major influence on egg laying by the queen.

‡ National … Ha! Most are only national if you live within the M25. Anywhere else and you’re usually much better off accessing some data from closer to home. It’s worth noting that the sort of ‘amateur’ weather stations I discuss do vary in data quality. For example, they’re a bit dodgy recording temperatures in full sun (they tend to over-read). However, if you find a local one, check the temperature in comparison to a thermometer in your apiary, you’ll find it’s a useful way to monitor what might be happening in the hives.

§ I don’t routinely generate these graphs – I have a life (!) – but did specifically to illustrate this post. It’s sufficient to simply monitor the average temperature.

Colophon

Whether the weather be fine
Or whether the weather be not,
Whether the weather be cold
Or whether the weather be hot,
We’ll weather the weather
Whatever the weather,
Whether we like it or not.

Anonymous