Tag Archives: beekeeping myths

Repeated oxalic acid vaporisation

Synopsis : Does repeated oxalic acid vaporisation of colonies rearing brood work sufficiently well? Is it as useful a strategy as many beekeepers claim?

Introduction

Oxalic acid is a simple chemical. A dicarboxylic acid that forms a white crystalline solid which dissolves readily in water to form a colourless solution. It was originally extracted from wood-sorrels, plants of the genus Oxalis, hence the name. In addition to the wood-sorrels it is present in a wide range of other plants including rhubarb leaves (0.5% oxalic acid 1 ), the berries and sap of Virginia creeper and some fruits, such as starfruit. Additionally, fungi excrete oxalic acid to increase the availability of soil nutrients.

Oxalic acid is inexpensive to produce by a variety of processes and was possibly the first synthesised natural product. About 120,000 tonnes are produced annually and it is mainly used for bleaching wood (and often sold as ‘wood bleach’) and cleaning products – including teeth. It chelates iron and so is used for rust removal and is used as a dye fixative (or mordant 2 ).

Spot the difference ...

Oxalic acid and API-Bioxal … the same but different

It is also, when used properly, devastatingly effective against the ectoparasitic mite Varroa destructor.

And, even more importantly, when used properly it is extremely well-tolerated by honey bees.

Great!

Not so fast …

Unfortunately for beekeepers, some of the commercially available i.e. licensed and approved, oxalic acid-containing treatments either contain unnecessary additives and/or have limitations in their approved modes of administration that reduces their efficiency and use in real world beekeeping situations.

Oxalic acid-containing miticides and their use

A quick search of the UK’s 3 Veterinary Medicines Directorate snappily titled Product Information Database for ‘target species = bees’ and ‘active ingredient = oxalic acid’ yields three products :

  • Varromed (BeeVital GmbH) which is a solution containing formic acid and oxalic acid
  • Oxybee (DANY Bienenwohl GmbH) which is an oxalic acid solution PLUS a separate powder containing essential oils and sugar. As far as I can tell, Oxybee looks to be the same product as Dany’s BienenWohl powder and solution, which – although listed and licensed – I cannot find for sale 4 in the UK
  • API-Bioxal (Chemicals Laif S.P.A) which is purchased as a powder composed of 88% oxalic acid dihydrate together with silica and glucose

I’m going to largely ignore Varromed and Oxybee for the rest of this post. I’m sure they’re perfectly good products but I’ve not used either of them so cannot comment from personal experience.

Keeping your powder dry

More relevant to this post, Oxybee and Varromed are both liquids, and this post is about vaporising (aka sublimating) oxalic acid.

And vaporisation involves using the powdered form of oxalic acid.

Which neatly brings me to the methods of application of oxalic acid-containing treatments to kill mites.

I’m sure there are some weird and wonderful ones, but I’ll be limiting any comments to just three which – from my reading of the instructions – are the only ones approved (and then not for all of the products listed above) : 5

  • Spraying a solution onto the surface of the bee-covered frames
  • Dribbling or trickling a solution onto each seam of bees between the frames
  • Vaporisation or sublimation of powdered oxalic acid by heating it in a metal pan to convert it to a gas. This permeates the hive, settling on all the surfaces – woodwork, comb, bees – and remains active against mites for a period after administration

Broodless is best

Oxalic acid, however it is administered, does not penetrate brood cappings. Therefore all of the approved products are recommended for use when the colony is broodless.

Typically – though not exclusively – this happens in the winter, but the beekeeper can engineer it at other times of the season.

If the colony is broodless you can expect any oxalic acid-containing miticide to reduce the mite population by 90% or more. There are numerous studies that support this level of efficacy and it’s what you should be aiming for to give the colony the best start to the season.

I discussed at length how to determine whether a winter colony is broodless a fortnight ago in Broodless?

This post is a more extensive response to several comments (made to that Broodless? article) that recommended repeated vaporisation of oxalic acid at, either 4, 5 or 7 day intervals.

The idea is that this kills the phoretic mites present when the colony is first treated and the mites subsequently released as brood emerges.

How many repeats?

I’ve seen anything from two to seven recommended online.

I’ll discuss this further below, but I’d note that the very fact that there’s such variation in the recommended repeat treatments – perhaps anything from two, fours days apart to seven at weekly intervals (i.e. spanning anything from 8 days to 49 days) – suggests to me that we don’t know the optimal treatment schedule.

Which is a little weird as, a) Varroa is a globally-distributed problem for beekeepers and is more or less invariant (as is the brood cycle of the host honey bee), and b) repeated treatment regimes have been used for over 20 years.

Which brings me back to a crude comparison of vaporisation vs dribbling, or …

Sublimation vs. trickling

A hive can be sublimated with oxalic acid without opening the hive. The vaporiser alone is introduced through the hive entrance or – in the case of certain models – the vapour is squirted through a hole in the floor, brood box or eke. In contrast, trickling oxalic acid requires the removal of the crownboard.

In the video above I’m using a Sublimox vaporiser. The hive entrance is sealed with foam and the open mesh floor is covered with a tightly fitting slide-in tray. As you can see, very little vapour escapes.

Although oxalic acid is well tolerated by bees, and it has no effect upon sealed brood, a solution of oxalic acid is detrimental to open brood. Therefore, trickled oxalic acid weakens the colony – because the acidity kills some or all of the open brood – and repeated trickling of oxalic acid is likely to compound this (see Al Toufailia et al., 2015). In contrast, repeated oxalic acid vaporisations appear not to be detrimental to the colony (caveat … I’m not aware of any long-term studies of this, or for the impact on the queen).

API-Bioxal approved methods of administration

The instructions for API-Bioxal clearly state that only a single treatment by vaporisation is approved per year. The exact wording is:

Maximal dose 2.3g per hive as a single administration. One treatment per year.

In contrast, when used as a solution for trickling the instructions state:

Up to two treatments per year (winter and/or spring-summer season in brood-free colonies).

This seems nonsensical to me considering what we now know about oxalic acid – remember, API-Bioxal was licensed in the same year (2015) that Al Toufailia et al., demonstrated it was detrimental to open brood, and I’m reasonably sure this had been shown previously (but can’t currently find the reference).

But, it gets worse …

API-Bioxal contains oxalic acid with powdered silica and glucose. I presume the silica is to keep it free-running. I’m not aware that powdered silica kills mites and I’m damned certain that glucose has no miticidal activity 😉 .

Neither of these two additives – which I’ve previously called cutting agents – are there to increase the activity of the oxalic acid … and the presence of the glucose is a real problem when vaporising.

Single use ...

Caramel coated Sublimox vaporiser pan

When glucose is heated to 160°-230°C it caramelises (actually, this happens at 150°C 6 ), coating the inside of the vaporising pan. This needs to be cleaned out afterwards 7. The instructions state:

Cool down and clean the vaporizer after use to remove possible residue (max 6%, around 0.140 g).

However, I don’t want to focus on what I consider to be a very effective but decidedly sub-optimal product … instead I want to discuss whether repeat treatment with oxalic acid actually works when there is brood present.

Why is repeat treatment recommended?

Remember, it’s not recommended or approved by the manufacturers of API-Bioxal or the Veterinary Medicines Directorate. I really should have titled this section ’Why is repeat treatment recommended by those who advocate it?’

But that wouldn’t fit on a single line 😉 .

When you sublimate oxalic acid, the gas cools and the oxalic acid crystals settle out on every surface within the hive – the walls, the frames, the comb, the bees etc.. For this reason, I prefer to vaporise oxalic acid when the colony is not tightly clustered. I want everything to be coated with oxalic acid, and I particularly want every bee to be coated because that’s where most of the mites are.

Unless they’re in capped cells 🙁 .

And if they’re in capped cells, the only way the Varroa (released when the brood emerges) will come into contact with oxalic acid is if it remains present and active within the hive. Unfortunately, it’s unclear to me exactly how long the oxalic acid does remain active, or what accounts for a drop in its activity.

But it does drop.

If you treat a colony with brood present and count the mites that appear on the Varroa tray every day it looks something like this:

Mite drop per day before and after treatment

’Something like’ because it depends upon the phoretic mite levels and the amount and rate of brood uncapping. For example, you often see higher mite drops from 24-48 hours than 0-24 hours after treatment.

I know not why.

The drop in the first 48 hours – presumably almost all phoretic mites – can be very much higher than the drop from day three onwards 8.

The duration of activity after vaporisation

Some studies claim oxalic acid remains active for 2-3 weeks after administration. I’m a little sceptical that it’s effective for that long and my own rather crude observations of post-treatment mite drop (of brooding colonies) suggests it returns to background levels within 5-7 days.

I could rabbit on about this for paragraphs as I’ve given it a reasonable amount of thought, but fortunately the late Pete Little did the experiment and showed that:

The recommended dose for colonies with brood is three or four doses seven days apart, however I found out that this is not effective enough, and treated 7, 6, 5 4, 3, 2 days apart to find out the most effective which is 5.

It therefore makes sense that three treatments at five day intervals should be sufficient. This period comfortably covers a complete capped brood cycle (assuming there is no drone brood in the colony) which is 12 days long.

Repeated oxalic acid vaporisation treatment regime.

If there is drone brood present you would theoretically need four treatments at 5 day intervals to be sure of covering the 15 day capped brood cycle of drones.

But it turns out there are some additional complications to consider.

Dosage

In the UK the recommended i.e. approved, maximum dose of API-Bioxal is 2.3 g by vaporisation. Remember my comments about the other rubbish stuff API-Bioxal contains, 2.3 g of API-Bioxal actually contains a fraction over 2 g of oxalic acid dihydrate.

This is the active ingredient.

When comparing different experiments where some have used ‘plain’ oxalic acid dihydrate and others have used – or will use – API-Bioxal, it’s important to consider the amount of the active ingredient only 9 .

In the US, oxalic acid was registered as an approved treatment for Varroa in 2015. By vaporisation, the approved dosage is 1 g of oxalic acid dihydrate per brood box i.e. half that approved in the UK.

Remember also that a deep Langstroth is 5% larger (by volume) than a National brood box.

And Jennifer Berry and colleagues in the University of Georgia have recently determined whether repeated administration of vaporised oxalic acid to a colony rearing brood is an effective way of controlling and reducing Varroa infestations (Berry et al., 2021).

And the answer is … decidedly underwhelming

Here are the experimental details.

The paper doesn’t state 10 when the experiment was done but they measured honey production in the treated colonies and were definitely brood rearing, so I’m assuming late summer.

Colonies were treated with 1 g / box (double Langstroth deeps) vaporised oxalic acid every five days for a total of 35 days i.e. 7 applications. Mite infestation levels (percent of workers carrying phoretic mites) were measured before and after treatment. Almost 100 colonies were used in the experiment, in three apiaries, randomly split into treated and control groups.

Let’s get the easy bit out of the way first … there was no difference in brood levels, adult bees or food stores at the end of the study. The treated hives were not disadvantaged by being treated … but they didn’t gain an advantage either 🙁 .

Mite levels after treatment normalised to pre-treatment levels (dotted line = no change)

During the experiment the percent mite infestation (PMI) levels in the untreated control colonies increased (as expected) by ~4.4. This is an average and there was quite a bit of variation, but it means that an initial mite infestation level of 4 (average) increased to 8.4 i.e. over 8 mites on every 100 adult workers in the hive.

3% is often considered the cutoff above which treatment is necessary.

Overall, the PMI of treated colonies reduced over the duration of the experiment … but only by 0.7.

From a colony health perspective this is a meaningless reduction.

Seven treatments with the recommended (in the US) dose of oxalic acid stopped the mite levels increasing, but did not reduce them.

Repeated administration of the US-approved oxalic acid dose by vaporisation does not reduce mite levels in a way that seems likely to significantly benefit the colony.

🙁

Dosage, again

I’m not sure the primary data used to justify the US approved 1 g / box dosage. Early studies by Thomas Radetzki (PDF) showed a 95% reduction in mite levels using a dose of 1.4 g. This was a large study involving ~1500 colonies and a dose of 2.8 g was not significantly more effective. I’m quoting the figures for broodless colonies 11.

The Berry results were similar to two smaller previous studies by Jamie Ellis and colleagues (Jack et al., 2020, 2021) who demonstrated that 1 g oxalic acid vaporised three times at weekly intervals was ineffective in controlling mite levels.

However Jack et al., (2021) also applied a similar treatment schedule using different doses of oxalic acid.

Data from Jack et al., 2021 using different repeat doses of oxalic acid

Ignore the intermediate values in panel A, just look at the pretreatment and ‘3 weeks’ mite infestation values.

Mite levels increased in untreated controls and decreased in all treated colonies. However, there was a clear dose response where the more oxalic acid used the greater the impact on the mite levels.

Four grams of oxalic acid reduced the mite infestation rate significantly … from ~5% to ~2% (I’ll return to this). However, the intermediate levels of oxalic acid, whilst reducing mite levels, did not do so significantly from the next closest amount of oxalic acid. For example, 1 g wasn’t significantly more effective than no treatment (as already stated), 2 g was not significantly more effective than 1 g and 4 g was not significantly more effective than 2 g.

But wait … there’s more

I’m familiar with two other studies that look at dose and/or repetition and efficacy (there are more, but this isn’t meant to be an exhaustive review, more a ”Do we know enough?” overview).

Gregoric et al., (2016) published a 12 study that appeared to use combinations of treatments in multiple apiaries. The abstract claims 97% reduction using three 1 g vaporisations, though these are spread over a 57 day period (!) stretching from mid-August to late-November. Mite drop in November following treatment was ~75% (presumably broodless) , but only 10-20% in August. Interestingly I can’t find the figure 97% anywhere in the results …

Finally, Al Toufailia et al., (2015) investigated the dose response to vaporised oxalic acid, showing an 80% reduction in infestation at 0.56 g and 93-98% who using 1.125, 2.25 and 4 g of oxalic acid. All of these studies were determined using broodless colonies.

The Al Toufailia and Jack studies – as well as the Berry study – also reported on adverse effects on the colony. With certain exceptions vaporisation was well tolerated. Some colonies went queenless. Where the queen was caged in late summer to render it broodless (Jack et al.,) some colonies subsequently failed to overwinter successfully (though, look on the bright side, mite levels were reduced 😉 ).

Don’t do that at home … I presume they impacted the production of winter bees.

confused.com

I’m not sure there’s a compelling, peer-reviewed study that definitively shows that repeat treatments of vaporised oxalic acid administered to a brood rearing colony reduces mite levels sufficiently.

Yes, the Jack et al., (2020) showed a significant reduction in the infestation rate (using 4 g three times at seven day intervals), but it was still around 2%.

In late summer, with 20-30,000 bees in the box and 6 frames of brood, that’s still ~600 mites (and potentially more in the capped brood).

In midwinter with about 10,000 workers and much smaller amounts of brood in the hive a 2% infestation rate is still 200 mites.

That’s still a lot of mites for a nearly broodless colony … I treat my colonies when broodless (and assume I’m killing ~90% of the mites present) and am disappointed if there are 45 mites on the Varroa tray. 50 mites on 10,000 workers is an infestation rate of 0.5%.

I’ve waffled on for too long.

All those advocating – or using – repeated oxalic acid vaporisation on brood rearing colonies in late autumn/winter need to think about:

  • dosage … 1 g is clearly too little (at a 5-7 day interval, but what if it was at a 4 day interval?), 2 g is better and 4 g is well-tolerated and certainly more effective
  • frequency … which I suspect is related to dosage. The goal must be to repeat sufficiently frequently that there is never a period when oxalic acid levels fall below a certain amount (and I don’t know what that amount is). 1 g on a daily basis might work well … who knows?
  • duration … you must cover a full capped brood cycle with the repeats
  • adverse effects … inevitable, but can be minimised with a rational treatment schedule

Broodless is best

It really is.

But, if your colonies are never broodless 13 then I wouldn’t be confident that repeat treatment was controlling Varroa levels sufficiently.

I have treated repeatedly with oxalic acid. In the good old days before API-Bioxal appeared. It certainly reduced Varroa levels, but not as well as my chosen Apivar does these days.

Repeated oxalic acid vaporisation is regularly proposed as the solution to Varroa but I’m certainly not confident that the data is there to support this claim.

Take care out there 😉


Notes

In a future post I’ll revisit this … I’ve got a pretty clear idea of how I’d go about demonstrating whether repeated oxalic acid treatments are effective in meaningfully reducing mite levels i.e. sufficient to protect the colony overwinter and through to the following late summer.

References

Al Toufailia, H., Scandian, L. and Ratnieks, F.L.W. (2015) ‘Towards integrated control of varroa: 2) comparing application methods and doses of oxalic acid on the mortality of phoretic Varroa destructor mites and their honey bee hosts’, Journal of Apicultural Research, 54(2), pp. 108–120. Available at: https://doi.org/10.1080/00218839.2015.1106777.
Berry, J.A. et al. (2022) ‘Assessing Repeated Oxalic Acid Vaporization in Honey Bee (Hymenoptera: Apidae) Colonies for Control of the Ectoparasitic Mite Varroa destructor’, Journal of Insect Science, 22(1), p. 15. Available at: https://doi.org/10.1093/jisesa/ieab089.
Gregorc, A. et al. (2016) ‘Integrated varroa control in honey bee (Apis mellifera carnica) colonies with or without brood’, Journal of Apicultural Research, 55(3), pp. 253–258. Available at: https://doi.org/10.1080/00218839.2016.1222700.
Jack, C.J., van Santen, E. and Ellis, J.D. (2020) ‘Evaluating the Efficacy of Oxalic Acid Vaporization and Brood Interruption in Controlling the Honey Bee Pest Varroa destructor (Acari: Varroidae)’, Journal of Economic Entomology, 113(2), pp. 582–588. Available at: https://doi.org/10.1093/jee/toz358.
Jack, C.J., van Santen, E. and Ellis, J.D. (2021) ‘Determining the dose of oxalic acid applied via vaporization needed for the control of the honey bee (Apis mellifera) pest Varroa destructor’, Journal of Apicultural Research, 60(3), pp. 414–420. Available at: https://doi.org/10.1080/00218839.2021.1877447.

Late season miscellany

I was struggling for a title for the post this week. It’s really just a rambling discourse on a variety of different and loosely related, or unrelated, topics.

Something for everyone perhaps?

Or nothing for anyone?

Beekeeping myths – bees don’t store fondant’

I only feed fondant in the autumn. I discussed how and why a month ago. Inevitably some people question this practice.

I’ve heard that bees don’t store fondant, don’t they just eat it when needed?

‘X’ (a commercial/old/decorated/opinionated beekeeper) assures me that bees do not store fondant.

Many beekeepers, even experienced beekeepers, seem to be under the impression that bees will not store fondant.

All gone!

So, let’s correct that ‘fact’ for starters, and file it forever where it belongs … in 101 Beekeeping Myths.

I added a single 12.5 kg block of fondant to all my colonies on the 28th of August. I checked them again on the 2nd of October (i.e. exactly 5 weeks later). About 80% had completely emptied the bag of fondant. All that remained was the empty blue plastic ‘husk’.

The few that had not completely emptied the bag were ~75% through it and I expect it to be all gone in a week or so.

Blue plastic ‘husks’ from ~60 kg of fondant.

So where has the fondant gone?

There are only two options 1. They’ve either eaten the fondant and used it to rear new brood, or stored it.

That amount of fondant is far more than they could consume and not rear lots of brood. So, it’s gone somewhere …

The weather has been OK. Bees are still gathering pollen and a small amount of late season nectar. They’ve not been locked away for a month just scoffing the fondant to keep warm.

They have been rearing brood – see below – but in ever-diminishing amounts, so this is unlikely to account for those empty blue bags.

But the biggest giveaway is the fact that the hives are now very heavy and almost every frame is packed solid with stores – again, see below.

The hives are actually very much heavier than they were at the end of August.

There’s not enough late season nectar flow to account for this increase in weight. There are also empty fondant bags on the top bars.

Although correlation does not necessarily imply causation, in this case, it does 😉

Bees do store fondant 2. It’s just sugar, why wouldn’t they?

Wall to wall brood stores

Out of interest I opened a couple of colonies to check the levels of stores and brood.

I only did this on colonies that had finished eating storing the fondant. Assuming the hive is heavy enough I remove the empty bag and the queen excluder from these, prior to closing the hive up for the winter. If they are still underweight I add another half block.

And another … all gone!

A 10-frame colony in the bee shed was typical. This was in a Swienty National poly brood box. These colonies are oriented ‘warm way’ and inspected from the back i.e. the opposite side of the hive to the entrance.

The first six frames were packed with capped stores.

Nothing else.

No brood, no gaps, nothing. Solid, heavy frames of nothing but stores.

The seventh frame had a small patch of eggs, larvae and a few open cells. In total an area no larger than my rather modestly sized mobile phone 3. Other than some pollen, the rest of the frame was filled with stores, again all capped.

Frame eight had a mobile-phone sized patch of sealed brood on both sides of the frame, with the remainder being filled with stores.

The ninth frame looked like the seventh and I didn’t bother checking the last frame in the box as the front face of it looked like it was just packed with stores.

I accept that the far side of that frame could have been a huge sheet of sealed brood, but I doubt it. This colony hadn’t been opened for more than a month, so the brood nest had not been rearranged by my amateur fumbling … it’s just as the bees had arranged it.

So, in total, the colony had less brood (eggs, larvae and capped) than would comfortably fit on a single side of one frame i.e. less than one twentieth of the comb area available to them. The rest, almost every cell, was sealed stores.

On the basis that a capped full National brood frame contains ~2.3 kg of stores 4 then this brood box contained about 22 kg of stores, which should be sufficient to get them through the winter.

Apivar strips

I treated all these colonies with Apivar at the same time as I fed them. Apivar needs to be present for 6-10 weeks, so it is still too soon to remove the strips.

However, it’s worth checking the strips haven’t been propolised up, or got embedded into the comb they’re adjacent to.

Apivar strip on wire hanger

Apivar is a contact miticide. The bees need to walk back and forwards over the strips. Therefore, if parts of the strips are gummed up with propolis, or integrated into comb, the bees will not have access.

Apivar strip partially gummed up with wax and propolis

You may remember that I tried hanging the strips on wire twists this season (see photo), rather than using the integrated plastic ‘spike’ to attach them to the comb. These wire hangers have worked well, for two reasons:

  1. The strips are more or less equidistant between the flanking combs. They are therefore less likely to get integrated into the comb 5, consequently …
  2. They are a lot easier to remove 🙂

I checked all the strips, scraping down any with the hive tool that had been coated with wax or propolis. This should ensure they retain maximal miticidal activity until it is time to remove them 6.

Scraped clean Apivar strip … ready for a couple more weeks of mite killing

And, it’s worth stressing the importance of removing the strips after the treatment period ends. Not doing so leaves ever-reducing levels of Amitraz (the active ingredient) in the hive through the winter … a potential mechanism for selecting Amitraz-resistant mites.

Au revoir and thanks for the memories

Other than removing the Apivar strips in a couple of weeks there’s no more beekeeping to do this year. And that task barely counts as beekeeping … it can be done whatever the weather and takes about 15 seconds.

As stressed above, it is an important task, but it’s not really an opportunity to appreciate the bees very much.

It must be done, whatever the weather.

Last Friday was a lovely warm autumn afternoon. The sun was out, the breeze was gentle and the trees were starting to show their fiery autumn colours. The bees were busy, almost self-absorbed, and were untroubled by my visit. It was a perfect way to wrap up the beekeeping year.

Like Fred commented last week, these last visits to the apiaries are always tinged with melancholy. Even in a year in which I’ve done almost no beekeeping, I’ve enjoyed working with the bees. It’s at this time of the season I realise that it’s a long time until April when I’ll next open a hive.

And, when you think about it, the active part of the season is shorter than the inactive part in northern latitudes 🙁

It was reassuring to see strong, healthy colonies showing no defensiveness or aggression. My split them and let them get on with it approach to queen rearing this season seems to have gone OK. With 2020 queens in most of the colonies I’ll hope (perhaps in vain) for reduced swarming next spring. I’m pretty certain that the colonies that were not requeened this year (under non-ideal conditions) generated more honey because there was no brood break while the new queen got out and mated.

Securely strapped up for the winter.

I’m confident that the colonies have sufficient stores and are all queenright. The mite levels are low – some much lower than others as I will discuss in the future – and the hives are securely strapped up for the winter ahead.

There’s no smoke without fire

And now for something completely different.

I’ve acquired a third main apiary this year and, because of its location, cannot carry equipment back and forwards all the time. I’ve therefore had to duplicate some items.

A little smoker

I didn’t want to shell out £60+ on a yet another Dadant smoker so dug out my first ever smoker from the back of the shed. I think this was originally purchased from Thorne’s, though not by me as I acquired it (at least) second hand, and it’s not listed in their catalogue any longer.

It’s a bit small and it has a tendency to go out, either through running out of fuel or simply because the ‘resting’ airflow is rather poor.

Consequently I often have to relight it.

I’m a big fan of using a blowtorch to light a smoker. If you get an auto-start model they work whatever the weather.

Or, more specifically, whatever the wind.

Trying to relight a recalcitrant smoker on a windy day with matches in the presence of a stroppy colony is not my idea of fun.

Of course, my colonies aren’t stroppy, but if they were going to be it would be when all I had was a box of matches in a strong breeze 😉

Rather than buying an additional blowtorch I instead purchased a kitchen or chef’s blowtorch, designed to produce the perfect crème brûlée. It was a ‘Lightning Deal’ for under £7 from Amazon. Even at full price it’s still only half the price of a cheap DIY blowtorch.

Blowtorch

It’s easy to fill, lights first time and immediately produces a focused blue flame. In contrast, my DIY blowtorch needs to warm up for 30 s. to change from billowing yellow 7 to an intense blue flame.

The chef’s blowtorch is also small enough to fit inside the same box I store/carry smoker fuel in. There is a lock to either prevent inadvertent ignition, or to produce an ‘always on’ flame.

If it survives the adverse environment of my bee bag it will be money well spent.

If not, I’ll make some crème brûlée 😉

There’s no smoke without fuel

Thorne’s had a late summer sale a fortnight or so ago. My order was finally shipped and arrived during a week when I was away and it was raining (two facts that are not unconnected … I’d disappeared to check my bees on the other side of the country where the weather was better).

The order sat outside in the rain and looked rather forlorn when I returned. Nothing was water damaged, not least because of the huge amounts of shredded packing protecting the contents.

Drying tonight

This stuff makes good smoker fuel. You just tear a handful off and stuff it in the smoker. It’s easy to light, smoulders well and doesn’t smell too acrid.

At least, once it’s dry it has all those desirable characteristics.

It’s now laid out drying on top of my canoe in the shed. I’m not even sure how they got so much in the delivery box. It looks like several cubic feet laid out like that, possibly enough for all of next year.

Waxworks

Although I’ve singularly failed to cycle a lot of old dark frames out of my colonies this year, I have managed to accumulate a lot of frames that need melting down. Some are old and dark, others are all drone comb in foundationless frames, and some are from a colony with a dud queen. I’d also accumulated quite a bit of burr or brace comb during my few beekeeping days of the season.

There’s not a lot of wax in most brood frames and the wax you can extract is rather dark. However, it’s perfectly acceptable to trade in for fresh foundation and makes very satisfactory firelighters.

Thorne’s Easi-Steam in action

And, after you extract the wax and clean up the frames you can reuse them. Simply add fresh foundation and you save yourself the drudgery of frame making. Result 😉

Or, if you use foundationless frames, you can just reuse them. Even better 🙂

A couple of years ago I treated myself to a Thorne’s Easi-Steam. I bought it without the steam generator as I already had one from my earlier homemade wax extractor 8. With the help of a mate who is a plumber I got the right sort of brass connectors to fit my steam generator to the Easi-Steam and I was ready to go.

Frames and brace comb ready for extraction

The Easi-Steam consists of a metal roof, a deep lower eke and a mesh and metal floor that needs a solid wooden floor underneath (which isn’t provided). You put it all together, add a brood box (almost) full of frames and fire up the steamer … then watch as the wax drips out into a bucket. ‘Almost’ because the brass connector stands proud and fouls the top bars of the frames 9, so you need to leave a gap.

It works well and leaks less than my homemade extractor. The recovered wax is remelted, cleaned up briefly, refiltered and is then ready for trading in or turning into firelighters.

This is all small scale stuff. With an oil drum, a big heater and an old duvet cover you can do much more, much faster. But I don’t need that capacity, or have the space to store the gear for the 363 days of the year it’s not being used.

The finished product

Here’s some I made earlier

There’s a long winter ahead and I think the time invested in wax extraction is more than justified when I …

  • Return from Thorne’s of Newburgh with 200 sheets of premium foundation having ‘paid’ with a just few kilograms of wax
  • Ignite another pile of felled rhododendron logs with a homemade fire lighter
  • Use the time I would have been making frames to do something more enjoyable 10

 

Weed and feed

Weed and feed is a generic term that describes the treatment of lawns to simultaneously eradicate certain weeds and strengthen the turf.

It seemed an appropriate title for a post on eradicating mites from colonies and feeding the bees up in preparation for the winter ahead.

Arguably these are the two most important activities of the beekeeping year.

Done properly they ensure you’ll still be a beekeeper next year.

Ignored, or done too little and too late, you’ll join the unacceptably large number of beekeepers who lose their colonies during the winter.

They think it’s all over

In Fife, on the east coast of Scotland, my beekeeping season effectively finishes with the midsummer ‘mixed floral’ nectar sources. This is a real mix of lime, blackberry, clover and Heinz nectars 1 … many of which remain to be identified.

There’s no reliable late nectar flow from himalayan balsam around my apiaries are and not enough rosebay willowherb (fireweed) to be worthwhile, though in a good year the bees continue to collect a bit from both into early September.

But by then the honey supers are off and extracted. Anything the bees find after that they’re welcome to.

The contrast with the west of Scotland is very marked. Over there my bees are still out collecting reasonable amounts of late heather nectar, though the peak of the flow is over.

Storing supers

Once the honey supers are extracted they can be returned to the colonies for the bees to clean up prior to storing them overwinter. However, this involves additional trips to the apiary and usually necessitates using the clearer boards again to leave them bee-free before storage.

I used to do this and quite enjoyed the late evening trips back to the apiary with stacks of honey-scented supers. More recently I’ve stopped bothering and instead now store the supers ‘wet’. The main reasons for this are:

  • laziness lack of time
  • unless you’re careful it can encourage robbing, by wasps or bees. You need to return supers to all the colonies in the apiary and if you have the hives open too long it can induce a frenzy of robbing 2
  • the honey-scented supers encourage the bees to move up faster when they’re used the following season

If you do store the supers ‘wet’ make sure the stacked boxes are bee and wasp-tight. Mine go in a shed with a spare roof on the top. If there are any gaps the wasps, bees or ants will find them and it then becomes very messy. 

I know many beekeepers who wrap their supers in clingfilm. Not the 30 cm wide roll you use in the kitchen but the sort of metre wide swathe they used to wrap suitcases in at London Heathrow.

Dated super frames

The drawn super comb is a really valuable resource and can be used again and again, year after year. I usually record the year a frame was built on the top bar. Many are now over a decade old and have probably accommodated at least 80 lb of honey in their lifetime 3.

The timing of late season Varroa management

During the brood rearing season the Varroa levels in the colony will have been rising inexorably. Without intervention the mites will continue to replicate on developing pupae that would otherwise emerge as the all-important overwintering bees. These are critical to get the colony through to the following spring.

When Varroa feeds on a developing pupa it transmits the viruses – primarily deformed wing virus – it acquired from the last bee is fed on. These viruses amplify by about a million-fold within 24-48 hours. Pupae that do not die before eclosion may have developmental defects. Importantly, those that appear normal have a reduced lifespan.

The overwintering bees should live for months, but might only live for weeks if their virus levels are high.

And if enough overwintering bees have high viral loads and die prematurely, the probability is the the colony will perish in the winter.

You therefore need to reduce mite levels before the overwintering bees are exposed to Varroa

The full details and justification are in a previous post logically entitled When to treat?

TL;DR 4late August to early September is the best time to treat to protect the winter bees from the worst of the ravages of mite-transmitted DWV.

Use an appropriate treatment

You need to reduce the mite levels in the colony by at least 90% to protect the winter bees.

To achieve this you need an appropriate miticide used properly. 

I use Apivar

Apivar is an Amitraz-containing miticide. Although there are reports of mite resistance in some commercial apiaries, the pattern is very localised (individual hives within an apiary, which is difficult to understand) and in my view it is currently the best choice.

What are the alternates?

  • MAQS – active ingredient formic acid – poorly tolerated at high temperatures, but can be used with the supers present
  • Apiguard – active ingredient thymol – ineffective at lower temperatures (it needs an ambient temperature of 15°C to work – that’s not going to happen in Scotland in September).
  • Apistan – active ingredient a synthetic pyrethroid – unsuitable as there is widespread resistance in the mite population.

Using Apivar

Apivar treatment is temperature-independent. It cannot be used when the honey supers are present. You simply hang two strips in the hive for 6 to 10 weeks and let them do their work. The bees tolerate it well and, unlike MAQS or Apiguard, I’ve not seen any detrimental effects on the queen who continues to lay … making more of those important winter bees.

Apivar strips

Each strip consists of an amitraz-impregnated piece of plastic tape with a V-shaped tab that can be pushed into the comb to hold it in place. 

This generally works well as the frames are usually not moved much as there’s no need for inspections this late in the season.

Apivar strip pushed into comb

However, the strips can be a little fiddly to remove (or fall off during frame handling) and some of our research colonies will continue to be used for at least another month. I’ve therefore used a short piece of bent wire to hang the strips from in these hives.

Apivar strip on wire hanger

I place the strips in opposite corners of the hive, set two frames in from the sides. 

Apivar, wax and honey contamination

Although Amitraz is not wax soluble 5 there are recent reports on BEE-L that one of its breakdown products are, including one that has some residual miticide activity 6

I therefore try and get all the bees into the brood box before starting treatment (I described nadiring supers with unripe honey last week).

Very rarely I’ll leave the bees with a super of their own unripe honey. Usually this happens when the brood box is already packed with stores and overflowing with bees. In this case I’ll mark the super and melt down the comb next season rather than risking tainting the honey I produce.

I attended a Q&A session by the Scottish Beekeeping Association last month in which the chief bee inspector discussed finding Apivar strips in honey production hives. He described the testing of honey for evidence of miticide contamination and potential subsequent confiscation.

This is clearly something to be avoided.

Remember to record the batch number of Apivar used and note the date in your hive records. I just photograph the packet for convenience. The date is important as the strips must be removed after 6 weeks and before 10 weeks have elapsed. 

It’s finally worth noting that the instructions recommend scraping the strip with a hive tool part way through the period if they are being used for the full ten week course of treatment. The strips usually get propolised into the frame and the scraping ‘reactivates’ them to ensure that the largest possible number of mites are killed off.

And, after all, that’s what they’re being used for.

Apivar is expensive

Well … yes and no.

Yes it feels expensive when walking out of Thorne’s of Newburgh clutching one small foil packet and being £31 poorer. 

But think about it … that packet is sufficient to treat 5 colonies.

Is £6.20 too much to spend on a colony?

My 340 g jars of honey cost more than £6.20 and my productive colonies produce at least one hundred times that amount of honey. 

I don’t think 1% of the honey value is too much to spend on protecting the colony from mites and the viruses they carry.

Mite drop

Varroa killed by the miticide 7 fall to the bottom of the hive. If you have an open mesh floor (OMF) they fall through … onto the ground or the intervening neatly divided Varroa tray, enabling you to easily count them

Varroa trays ...

Varroa trays …

Remember that amitraz, the active ingredient of Apivar, works by direct contact. This is why you place the strips diametrically opposite one another so that as many bees as possible contact them. Unlike Apiguard, it makes no difference whether the Varroa tray is present or not.

It is useful to ‘count the corpses’ to get an idea of the infestation level and the efficacy of the treatment.

I’m going to discuss what you might expect in terms of mite drop in the winter (I need to plot some graphs first). However, this is something you could think about before then … knowing Apivar kills mites in less than three hours after exposure, what do you think the mite drop should look like over the 6-10 weeks of treatment?

Enough weeding, what about feeding?

I treat and feed colonies on the same day.

I also do the final hive inspection of the season. At this I look for evidence of a laying queen, the general health of the colony, the amount of brood present and the level of stores in the brood box. 

If the colony is queenless (how did that happen without me noticing earlier?) I simply unite the colony with a strong, healthy queenright colony. I don’t bother testing it with a frame of eggs … time is of the essence.

It’s too late to get a queen mated (at least in Fife … when I lived in the Midlands I got a few September queen matings but they could not be relied upon) and I rarely, if ever, buy queens.

I only feed with fondant in the autumn.

Convenience food

I described fondant last week as a convenience food

A spade's a spade ...

A spade’s a spade …

I’ve described in detail many of the benefits of fondant in numerous previous posts. Essentially these can be distilled to the following simple points:

  • zero preparation; no syrup spillages in the kitchen, no marital strife.
  • bucket- and feeder-free; no need to carry large volumes of syrup to the apiary and no feeders to store for the remaining 11 months of the year. All you need to feed fondant is a queen excluder and an empty super … and you’ve got those already.
  • easy to store; unopened it keeps for several years 8.
  • super speedy; I can feed a colony, including cutting the block in half, in less than 2 minutes.
  • good for queen and colony; perhaps that’s stretching it a bit. What I mean is that the bees take the fondant down more slowly than syrup, consequently the queen continues to lay uninterrupted as the brood nest does not get backfilled with stores. This is good for the colony as it means the production of more winter bees.
  • an anti-theft device; you can’t spill fondant so there is much less chance of encouraging robbing by neighbouring bees or wasps.
  • useful boxes; the empty boxes are a good size to store or deliver jarred honey in – each will accommodate sixteen 1 lb rounds.

I’ve fed nothing but fondant for about a decade and can see no downsides to its use.

Money, money, money

I’ve never used anything other than commercially purchased “baker’s” fondant … don’t believe the rubbish (about ‘additives’) some of the bee equipment suppliers use to justify their elevated prices.

You should be paying about £1/kg … any more and you’re being robbed. This year (2020) I paid less than 90p/kg.

Do not use the icing fondant sold by supermarkets for Christmas cakes. I’m sure there’s nothing much wrong with it, but – at £2/kg – you’ll soon go bankrupt. 

Tips for feeding fondant

Fondant blocks are easier to slice in half if they are slightly warm.

Use a sharp bread knife and don’t slice your fingers off. 

You can cut the blocks in half in advance in the warmth of your kitchen and then cover the cut faces with clingfilm to prevent them reannealing, but I just do it in the apiary.

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

Alternatively, use a clean spade 9.

Always place the block cut face down on a queen excluder directly over the top bars of the brood frames. With a full block, it’s like opening a book and laying it face down. Do not place it above a crownboard with a hole in it.

You want the bees to have unfettered access to the open face of the fondant block.

Fondant on queen excluder with eke

Ideally, use a framed wire queen excluder.

These are easier to lift off should you need to go into the colony.

Which you don’t 😉

There’s no need to continue inspections this late into the season. Go and enjoy a week or two away in Portugal … or perhaps not 🙁

If you need to store an unused half block of fondant wrap the cut face in clingfilm.

All my colonies get one full block (12.5 kg) and many get a further half block, depending upon my judgement of the level of the stores in the hive.

Insulation

The bees will take the fondant down over 2 – 4 weeks. They do store it, rather than just using it as needed. By late September or early October all that will remain is the blue plastic husk. The photo below is from mid-October. This colony has had a ‘topup’ additional half block after already storing a full block of fondant.

They fancied that fondant

With cooler days and colder nights, you want to reduce heat loss by the colony and minimise the dead space above the bees into which the heat escapes.

Although bees take fondant down at lower temperatures than they do syrup, there’s no point in giving the colony more additional space to heat than they need.

Poly super and fondant ...

Poly super and fondant …

Depending upon the availability of equipment I do one or a combination of the following:

  • use a poly super to provide space for the fondant
  • compress the fondant (use your boot) into as little space as possible and you squeeze it into a 50 mm deep eke, which (conveniently) is the same depth as the rim on my insulated polcarbonate/perspex crownboards 10.
  • use an eke and an inverted perspex crownboard with no need to compress the fondant
  • add a 50 mm thick block of insulation above the crownboard, under the roof (which may also be insulated)

Fondant block under inverted perspex crownboard – insulation block to be added on top is standing at the side

Oh yes … before I forget … completely ignore any advice you might read on using matchsticks to provide ventilation to the hive 11.

They think it’s all over … it is now

That’s the end of the practical beekeeping for the season 🙁

If your colonies are strong and healthy, if the mite levels are low and they have sufficient stores, there’s almost nothing to do now until March 12

Now really is a good time for a beekeeper to take a holiday.

Make a note in your diary on the date you need to remove the Apivar strips

Write up your notes, pour a large glass of Shiraz and make plans for next season 🙂