Author Archives: David

Oxalic acid preparation

This is the second of three articles on midwinter treatment of colonies with oxalic acid to minimise Varroa levels. In a recent post I explained why a midwinter treatment was necessary, even if you’d treated three months earlier. Essentially this is because:

  • there will still be some residual Varroa, particularly if you treated in late summer rather than early autumn (and this post explains why early treatment is preferable)
  • midwinter is the time when brood levels are at a minimum, so most mites will be phoretic and readily accessible to the miticide treatment

Midwinter is the time to use oxalic acid-containing treatments. It can be delivered in a variety of ways; by sublimation (vaporisation), spraying or trickling (dribbling).

Trickling or dribbling

This post is about the preparation and storage of oxalic acid-containing solutions for trickling. Sublimation is covered elsewhere and spraying is not approved or widely used in the UK.

The process for trickling is very straightforward. You simply trickle a specific strength oxalic acid solution in thin syrup over the bees in the hive. The oxalic acid kills the mites. How isn’t entirely clear – it’s thought to corrode the mouthparts and soft tissue. It’s more than 90% effective in killing phoretic mites when used like this.

Beekeepers have used oxalic acid for years as a ‘hive cleaner’, as recommended by the BBKA and a range of other official and semi-official organisations. All that changed when Api-Bioxal was licensed for use by the Veterinary Medicines Directorate (VMD).

Oxalic acid and Api-Bioxal, the same but different

Spot the difference ...

Spot the difference …

Api-Bioxal is the VMD-approved oxalic acid-containing miticide. It is widely available, relatively inexpensive (when compared to other VMD-approved miticides) and very easy to use.

It’s very expensive when compared to oxalic acid purchased in bulk.

Both work equally well as both contain exactly the same active ingredient. Oxalic acid.

Api-Bioxal has other stuff in it (meaning the oxalic acid content is a fraction below 90% by weight) which actually makes it much less suitable for sublimation.

How much and how strong?

To trickle or dribble oxalic acid-containing solutions you’ll need to prepare it at home, store it appropriately and administer it correctly.

I’ll deal with how it is administered next time. This is all about preparation.

The how much is easy. You’ll need 5ml of oxalic acid-containing solution per seam of bees. In midwinter the colony will be reasonably well clustered and its likely there will be a maximum of only 8 or 9 seams of bees, even in a very strong colony.

Hold on … what’s a seam of bees?

Two seams of bees

Two seams of bees …

Looking down on the colony from above, a seam of bees is the row visible between the top bars of the frames.

Remember to prepare ~10% more than you think you need. You’ll inevitably spill some when using the Trickle 2 bottle to administer it to the colony. It’s not that expensive, so don’t risk running out.

And the how strong? The recommended concentration to use oxalic acid at in the UK has – for many years – been 3.2% w/v (weight per volume) in 1:1 syrup. This is less concentrated than is recommended in continental Europe (see comments below on Api-Bioxal).

My advice – as it’s the only concentration I’ve used – is to stick to 3.2%.

Listen very carefully, I shall say zis only once

A bit of basic chemistry coming up. Skip to the warning in red below and then the recipes if you want, but this explains some important things about working out how much to use.

The molecular formula of oxalic acid is C2H2O4. The molecular weight of oxalic acid is 90.03 g/mol. However, the oxalic acid you purchase – including Api-Bioxal – is the dihydrated form of oxalic acid.

Di as in two, hydrated as in water.

The molecular formula of oxalic acid dihydrate is C2H2O4.2H2O and oxalic acid dihydrate has a molecular weight of 126.07 g/mol.

Therefore the weight of oxalic acid in 1 g of oxalic acid dihydrate is 90.03/126.07 = 0.714 g.


Oxalic acid is toxic

  • The lethal dose for humans is reported to be between 15 and 30 g. It causes kidney failure due to precipitation of solid calcium oxalate.
  • Clean up spills of powder or solution immediately.
  • Take care not to inhale the powder.
  • Store in a clearly labelled container out of reach of children.
  • Wear gloves.
  • Do not use containers or utensils you use for food preparation. A carefully rinsed plastic milk bottle, very clearly labelled, is a good way to store the solution prior to use.

Recipes : oxalic acid

The standard recipe is 100 g water plus 100 g white granulated sugar. Mix well and then add 7.5 g of oxalic acid. The final volume will be 167ml i.e. sufficient to treat over 30 seams of bees, or between 3 and 4 strong colonies (including the 10% ‘just in case’).

This final concentration is 3.2% w/v oxalic acid … (7.5 * 0.714)/167 * 100 = 3.2. Check my maths.

0.01 g to 500 g

0.01 g to 500 g

If you have more colonies to treat, or have trouble weighing 7.5g, scale everything up ten-fold. Or buy a small, accurate set of digital scales – like these for £9 which work very well. 1 kg of sugar plus 1 kg (1 litre) of water requires 75 g of oxalic acid and makes 1.67 litres … enough to treat all the colonies in the association apiary.

Which is not such a bad idea. Make it up carefully once and share it with your fellow beekeepers. Storage details are provided below.

Recipes : Api-Bioxal

Warning – the recipe on the side of a packet of Api-Bioxal makes up a much stronger solution (4.4% w/v) of oxalic acid than has historically been used in the UK. Stronger isn’t necessarily better. The recipe provided is 35 g Api-Bioxal to 500 ml of 1:1 syrup. By my calculations this recipe makes sufficient solution at a concentration of 4.4% w/v to treat 11 hives. 

To make a 3.2% Api-Bioxal-based oxalic acid-containing solution using the 35 g pack of Api-Bioxal you need to mix the entire contents of the pack with 691 ml of 1:1 syrup.

Here’s the maths:

  • 35 g of Api-Bioxal contains only 22.14 g of oxalic acid. 88.6% of the 35 g is oxalic acid dihydrate (the remainder is cutting agents like glucose and powdered silica) and so the oxalic acid content is ((35 * 0.886) * 0.714) = 22.14 g.
  • To calculate the volume of syrup you need to divide it by the final percentage required i.e. (22.14 / (3.2/100)) = 691 ml. I don’t know the exact amount of sugar and water needed to make this amount … it’ll be about 430 g of each (I think).

A 35 g packet of Api-Bioxal is therefore sufficient to treat about 15 colonies (assuming 5 ml per seam, 8 seams per hive and 10% ‘just in case’) at the recommended concentration of 3.2% w/v.

Api-Bioxal is sold in three pack sizes (35 g, 175 g and 350 g). If you are wealthy enough to be able to purchase the larger pack sizes you’ve probably got your own beekeeper (or mathematician). Relax on your yacht while they do the calculations for you 😉

On the other hand … if you have a smaller number of colonies either make a full 35 g packet up and share it, or use accurate scales and the following table:

Api-Bioxal recipes for 3.2% OA trickling

Api-Bioxal recipes for 3.2% OA trickling


Storage of oxalic acid syrup at ambient temperatures rapidly results in the acid-mediated breakdown of sugars (particularly fructose) to generate hydroxymethylfurfural (HMF). As this happens the colour of the oxalic acid-containing solution darkens significantly.

This breakdown happens whether you use oxalic acid or Api-Bioxal.

Stored OA solution and colour change

Stored OA solution and colour change …

HMF is toxic to honey bees at high concentrations. Studies from ~40 years ago showed that HMF concentrations below 30 mg/l were safe, but above 150 mg/l were toxic1. HMF buildup is one way overheated honey is detected.

At 15°C HMF levels in OA solution can reach 150 mg/l in a little over a week. At room temperature this happens much faster, with HMF levels exceeding 150 mg/l in only 2-3 days. In the dark HMF levels build up slightly less quickly … but only slightly 2,3.

Only make up OA solutions when you need them.

If you must store your oxalic acid-containing syrup for any length of time it should be in the fridge (4°C). Under these conditions HMF levels remain well below toxic levels for at least one year. However, don’t store it for this long … use it and discard the excess. Don’t use discoloured oxalic acid solutions as they’ve been stored incorrectly and may well harm your bees.

Please re-read the comments above about the toxicity of oxalic acid. If you are going to store it in the fridge it must be very clearly labelled and there must be no chance that children can reach or open the container.


Api-Bioxal is the least expensive VMD-approved miticide and powdered oxalic acid is much, much cheaper. Both contain the same active ingredient, oxalic acid, which is highly effective against phoretic mites.

In midwinter, with very low levels (or no) of brood, a single oxalic acid-containing treatment minimises mite levels for the coming season.

Oxalic acid-containing solutions are easy to prepare. I recommend you make sufficient for your own colonies and those of your beekeeping friends and association members. My previous BKA used to distribute litres of the stuff for use in midwinter. Use this solution in midwinter and then discard any that is unused.

Oxalic acid-containing solutions are inexpensive and easy to administer by trickling. As I shall demonstrate next time.

Please re-read the safety instructions highlighted in red above.

Michelle Dubois

Michelle Dubois

† Listen very carefully, I shall say zis only once was a catchphrase used by “Michelle of the Resistance” in the 1980’s comedy ‘Allo ‘Allo! Michelle (Dubois) was rarely seen without a trench coat and beret, had a corny French accent and was played by Kirsten Cooke.

‘Allo ‘Allo! ran for 85 episodes in the decade from 1982 on BBC one. It was about a café in Nazi-occupied France and the French Resistance, just about. It mixed bawdy humour with gross stereotypes (posh British twits, sex-obsessed French) and was a parody of ITV’s series Secret Army (’77-’79).

Early episodes had obvious and rather dull titles. In the later series the individual episodes had some quite good puns like Awful Wedded Wife.

Michelle – Listen very carefully, I shall say zis only once

René – Well, in that case, could you please speak slowly?

You had to be there … 😉

‡ Oh alright then, since you insist. The 175 g pack of Api-Bioxal (~£39) needs to be made up in 3.459 litres of 1:1 syrup and the 350 g pack (~£65) 6.919 litres of 1:1 syrup. Determining how much water and sugar to mix to make these amount is, as they say, an exercise for the reader. Assuming a 3.2% solution and 8 seams of bees per colony Api-Bioxal costs between 63p and 41p per hive (see note below), depending upon the pack size you purchase. I know that beekeepers moan on and on about the outrageous cost of Api-Bioxal (as do I), but is 63p per colony really an unreasonable amount to spend on VMD-approved medicines to keep your colony as clear of Varroa as possible? I don’t think so.

Note – the costs in the paragraph were calculated using the lowest prices I could currently find for Api-Bioxal. C Wynne Jones has the 35g packets for £9.50 and Maisemores have the 350g packets for £64.79. Prices correct on 9/10/17.

1 Jachimowich T., El Sherbiny G., Zur Problematik der verwendung von Invertzucker für die Bienenfüttering, Apidologie 6 (1975) 121-143.

2 Bogdanov S., Kilchenman V., Chamere J.D.. Imdorf A. (2001) available online.

3 Prandin, L., Dainese, N. , Girardi, B., Damolin, O., Piro, R., Mutinelli, F. A scientific note on long- term stability of a home-made oxalic acid water sugar solution for controlling varroosis Apidologie, 32:) 451-452


Kick ’em when they’re down

Out, damn'd mite ...

Out, damn’d mite …

Why bother treating colonies in midwinter to reduce Varroa infestation? After all, you probably treated them with Apiguard or Apivar (or possibly even Apistan) in late summer or early autumn.

Is there any need to treat again in midwinter?

Yes. To cut a long story short, there are basically two reasons why a midwinter mite treatment almost always makes sense:

  1. Mites will be present. In addition, they’ll be present at a level higher than the minimum level achievable, particularly if you last treated your colonies in late summer, rather than early autumn.
  2. The majority of mites will be phoretic, rather than hiding away in sealed brood. They’re therefore easy to target.

I’ll deal with these in reverse order …

Know your enemy

DWV symptoms

DWV symptoms

The ectoparasite Varroa feeds on honey bee pupae and, while doing so, transmits viruses (in particular DWV) that can completely mess up the development of the adult bee. Varroa cannot replicate anywhere other than on developing pupae. It’s replication cycle, and the resulting mite levels in the colony, are therefore tightly linked to the numbers and availability of hosts … honey bee pupae.

If developing brood is available the mite can replicate. Under these conditions, newly emerged adult, mated, female Varroa spend a few days as phoretic mites, riding around the colony on young bees. They then select a cell with a late-stage larvae in, enter the cell and wait until pupation occurs. If developing worker brood is available each infested cell produces 1 – 2 new mites (drone cells produce 3+) and mite numbers increase very rapidly in the colony.

In contrast, if there’s no developing brood available, the mites have to hang around waiting for brood to become available. They do this as phoretic mites and can remain like this for weeks or months if necessary.

Therefore, when brood is in abundance and the queen in laying freely mites can replicate to very high levels. In contrast, when brood is limiting and the queen has reduced her egg laying to a   v  e  r  y     s  l  o  w     r  a  t  e     the mite cannot replicate and must be predominantly phoretic.

When does this happen?

Lay Lady Lay … or don’t

Ambient temperature, day length and the availability of nectar and pollen likely influence whether the queen lays eggs. When it’s cold, dark and there’s little or no pollen or nectar coming into the hive the queen slows down, or even stops, laying eggs.

About 8 days after she stops laying there will be no more unsealed brood in the colony. About 13 days after that all the sealed brood will have emerged (along with any Varroa). Therefore, after an extended cold period in midwinter, the colony will have the lowest level of sealed brood … and the highest proportion of the mite population will be phoretic.

Under normal (midsummer) circumstances about 10% of the mite population is phoretic. It’s probably unnecessary to state that, if there’s no brood available, 100% of the mites must be phoretic.

All licensed miticides work extremely well against phoretic mites.

Caveats, guesstimates, global warming and the Gulf Stream

Global warming

Global warming …

Whatever the cause, the globe is warming (irrespective of what Donald Trump tweets). Long, hard winters are getting less common (or perhaps even rarer, as they were never particularly common in the UK). In Central, Southern or Eastern Britain it’s possible that the colony will have some brood present all year. In parts of the West, warmed by the Gulf Stream, I’d be surprised if a colony was ever broodless. Only in the North is it likely that there will be a brood break in midwinter.

Most of the paragraph above is semi-informed guesswork. I don’t think anyone has systematically analysed colonies in the winter for the presence of sealed brood. Sure, many (including me) have opened colonies for a quick peek. Others will have peered intently at the Varroa board to search for shredded wax cappings that indicate emerging brood. The presence of brood will vary according to environmental conditions and the genetics of the bees, so it’s not possible to be dogmatic about these things.

However, it’s safe to say that in midwinter, sealed brood – within which the mites can escape decimation by miticides – is at a minimal level.

Reducing mite levels and minimal mite levels

Within reason, the earlier you apply late summer miticides, the better you protect the all-important overwintering bees from the ravages of viruses, particularly deformed wing virus. This is explained in excruciating detail in a previous post, so I won’t repeat the text here.

However, I will re-present the graph that illustrates the modelled (using BEEHAVE) mite levels.

Time of treatment and mite numbers

Time of treatment and mite numbers

The gold arrow (days 240-300 i.e. September and October) indicates when the winter bees are being reared. These are the bees that need to be protected from mites (and their viruses). Mite numbers (starting with just 20 in the hive on day zero) are indicated by the solid coloured lines. The blue, black, red, cyan and green lines indicate modelled mite numbers when the colony is treated with a miticide (95% effective) in mid-July, August, September, October or November respectively.

The earlier you treat, the lower the mite levels are when the winter bees are being reared. Study the blue and black lines.

This is a good thing.

In contrast, by treating very late (the cyan and green lines) the highest mite numbers of the season occur at the same time as the winter bees are being reared. A bad thing.

But … look also at mite numbers after treatment

Look carefully at the mite numbers predicted to remain at the end of the year. Early treatment leaves higher mite levels at the start of the following year.

This is simply because mites escaping the treatment at the end of summer have had an opportunity to reproduce during the late autumn.

This is why the additional midwinter treatment is beneficial … it kills residual mites and gives the colony the best start to the new calendar year§.

Kick ’em when they’re down

Early treatment protects winter bees but risks exposing bees the following season to unnecessarily high mite numbers. However, in midwinter, these residual mites are much more likely to be phoretic due to a lack of brood in the colony. As I stated earlier, phoretic mites are relatively easy to target with miticides.

So, give the mites a hammering in late summer with an appropriate and effective miticide and then give those that remain another dose of the medicine in midwinter.

But not another dose of the same medicine

Since the majority of mites in a colony with little or no brood will be phoretic, you can easily reduce their numbers using a single treatment containing oxalic acid. This can be administered by sublimation (vaporisation) or by trickling (dribbling).

There’s no need to use any treatment that needs to applied for a month. Indeed, many (Apiguard etc.) are not recommended for use in winter because they work far less well on a largely inactive colony.

Trickle 2 - £1

Trickle 2 – £1

I’ve discussed sublimation previously. However, since this requires relatively expensive (£30 – £300) specialised delivery and personal protection equipment it may be inappropriate for the two hive owner. In contrast, trickling requires almost no expensive or special equipment and – reassuringly – has been successfully practised by UK beekeepers for many years. I did it for years before I bought my Sublimox vaporiser.

Therefore, in two further articles this autumn (well before you’ll need to treat your own colonies) I’ll describe the preparation and storage of oxalic acid solutions and its use.

Be prepared

If you want to be prepared you’ll need to beg, borrow or steal the following – sufficient oxalic acid (or Api-Bioxal), a Trickle 2 bottle sold by Thorne’s, a cheap vacuum flask (Tesco £2.50), granulated sugar and a pair of thin disposable gloves.

Do this soon. Don’t leave it until midwinter. You need to be ready to treat as soon as there’s a protracted cold spell (when brood will be at a minimum). Over the last few years my records show that this has been anywhere between the third week in November and the third week in January.

More soon …

† Only MAQS is effective against mites sealed in cells. This is why most miticides are used for extended periods in the late summer or early autumn … the miticide must be present as Varroa emerge from sealed cells.

‡ I’ll repeat the caveat that this is an in silico simulation of what happens in a beehive. Undoubtedly it’s not perfect, but it serves to illustrate the point well. It’s freely available, runs on PC and Mac computers, and is reasonably well-documented. In the simulations shown here the virtual colony was ‘primed’ with 20 mites at the beginning of the year. BEEHAVE was run using all the default settings – climate, forage etc. – with the additional application of a miticide (95% effective) in the middle of the months indicated. Full details of the modelling have already been posted.

§ The National Bee Unit recommend Varroa levels are maintained below 1000 throughout the season. Without treatment, 20 mites at the start of the season can easily replicate to ~750 in the autumn. If you start the season with 200 mites then levels are predicted to reach ~5000 in the following summer. The colony will almost certainly die that season or the next. There’s a more detailed account of the consequence of winter brood rearing and the level of mite infestation written by Eric McArthur and reproduced on the Montgomeryshire BKA website that’s worth reading.

¶ The cumulative (year upon year) effect of late summer treatment with no midwinter treatment has been discussed previously. I’ll simply re-post the relevant figure here – 5 years of bee (in blue, left axis) and mite (in red, right axis) numbers with only one treatment per season applied in late September. Within two years the higher mite numbers that are present at the start of the year reproduce to dangerously high levels.

Mid September

Mid September

Landing boards

I’ve bought and used a number of Abelo poly hives this season. I’m going to review these once I see how the colonies perform overwinter. However, one of their ‘features’ is an integral landing board that forms part of the removable floor (colonies 1 and 3, facing, below).

Abelo poly National hives ...

Abelo poly National hives …

Landing boards are great. They provide a large flattish or gently sloping ramp that leads to the hive entrance. There’s something mesmerising about watching heavily-laden foragers performing an inelegant ‘tail-down’ crash-landing several inches short of the entrance, righting themselves, and marching purposefully forwards into the gloom of the hive.

During a heavy nectar flow this happens dozens of times a minute, with a strong colony making about 35,000 foraging trips per day. It’s great to rest your elbows on the hive roof, peer over the top and watch hundreds of foragers bringing the nectar back, 40 milligrams at a time.

Integral landing boards and DIY

Mine's bigger than yours

Mine’s bigger than yours

Landing boards must be popular with other beekeepers as well as they regularly feature in commercially available hives. The Abelo implementation is relatively neat, projecting perhaps 5cm from the front face of the hive.

Other variants are rather more in-your-face. The version in the image on the right is on an early variant of a Maisemore’s poly National hive (I think – please correct me if I’m wrong – Matt Harris helpfully corrected me here … they’re Paynes hives). Frankly, I think it looks pretty ghastly, but at least returning foragers could crash-land some distance away and still walk the last few hundred yards unimpeded 😉

If your hives are cedar you can easily add a flat or sloping landing board to the front of the floor. If you’re going to do this use reasonable quality wood – the exposed edge of a strip of plywood tends to delaminate pretty quickly. Alternatively, build something cheap, functional and easily replaceable from Correx.

Thorne's budget hive ...

Thorne’s budget hive …

The bee shed houses up to 6 colonies, each with a simple short ‘tunnel’ ending in a 1-2″ aperture in the vertical shed wall. I’ve built simple Correx landing boards on these and they’ve performed extremely well over the last two years. Each piece of folded Correx is a distinctive colour to aid the bees returning to the correct hive.

Landing boards ...

Landing boards …

If you take advantage of abandoned ‘For Sale’ signs you can get Correx in a wide range of contrasting colours which saves having to spray paint them before use.

Take a stand

Landing boards don’t need to be attached to the hive front or floor. Some of our early research colonies were housed in lovely cedar hives built by Pete Little of Exmoor Bees & Hives. He provided stands with integral sloping landing (‘alighting’) boards. These are great, though they extend the need for compatibility from the hive itself to the stand as well.

Stand and integral landing board

Stand and integral landing board …

Nice, but not needed

Despite the pleasure to be gained from watching bees return to the hive entrance, landing boards aren’t really necessary and they can get in the way.

Feral colonies generally don’t have the benefit (or need) of a nicely sloping landing board. They cope admirably with a simple unadorned hole through the soffit, with nothing more than the painted boards to cling to … upside down. Crevices or holes in trees, or the church tower, probably have ‘grippy’ surfaces that aid arrival, but there’s no evidence they’re selected on any criteria other than the volume and overall location of the potential new ‘home’.

I used to build my preferred floor – the kewl floor with a mouse-proof and wasp-resistant ‘L’ shaped underfloor entrance – with a shallow integral Correx or plywood landing boards.

Original design

However, over time these all got damaged in transit, or I got sick of bees wandering underneath the floor if they landed on the stand, not the landing board. I’ve recently described a modified entrance to these kewl floors, again made from Correx, that is a marked improvement.

Correx landing board ...

Correx landing board …

There’s a very short video on the page describing these modified entrances showing bees landing and entering the hive perfectly well.

Damaged in transit … or in a pile (up)

The main problem with any sort of protruding landing board is that, by definition, it protrudes.

It therefore gets in the way.

It makes strapping hives up during transport more difficult and means the hives don’t stack together quite as neatly. I only move small number of colonies about, so it’s the inconvenience, not the space, that is the issue.

Abelo hives in transit ...

Abelo hives in transit …

Similarly, during the winter or after uniting colonies in the season, spare floors and other pieces of kit need to be neatly stacked out of the way. Protruding landing boards prevents them being placed on the top of the stack (because the roof fouls the landing board) and – in certain orientations – stops stacks being pushed close together.

Stacked boxes

Stacked boxes …

As an aside, you probably don’t want these floors at the bottom of the stack. Firstly, you’ll inevitably need one when putting together a new hive and it’s easiest not to have to remove the entire stack to access the floor. Secondly, unless blocked off with a sheet of polythene or Correx, they’ll allow wasps and bees access to the stack … or even encourage a swarm to move in.

So … over the years landing boards on my hives have evolved or, more accurately, atrophied. They’re now only present on the outside of the bee shed, on purchased poly hives and, in a rather truncated version, at the cavernous mouth of the Thorne’s Everynucs that I favour.

No landing boards here ...

No landing boards here …

Asian hornet 2017

Last month I wrote about the discovery and predicted spread of the Asian hornet (Vespa velutina) once (if) it gets established in the UK.

New Asian hornet isolation in North Devon

The National Bee Unit (NBU) and DEFRA have today (26th September 2017) reported the identification of an Asian hornet in the Woolacombe area of North Devon. This is about 100 miles from the Tetbury site (near Stroud) where the Asian hornet was isolated in September last year. There was an additional isolation in North Somerset in autumn 2016, though the precise location was not publicised.

Asian hornet

Asian hornet …

Genetic analysis by the NBU will determine whether the new isolate is related to previous isolates. This would imply, though not prove, that the hornet may be established and breeding on mainland UK.

I’m speaking at the Devon Beekeepers Convention in Totnes next month and expect to hear more about efforts to track down and destroy the (or nests) at the meeting.

The Asian hornet appears to now be established on Jersey in the Channel Islands.

Light my fire

If something is described as a “A triumph of form over function it looks better than it works. Here’s the diametric opposite – something that works really well, but looks a bit rubbish.

Re-using dark wax

Wax extracted from old brood frames is often too dark to use for candle making. You can exchange it for cash or new foundation at Thorne’s – either at one of their regional stores or at the big beekeeping conventions. However, if you use a lot of foundationless frames you’re unlikely to need much foundation (by definition 😉 ). If you have the patience of a saint you could consider making your own starter strips. As an alternatively you use can this old, dark wax to prepare perfectly good firelighters for a wood burning stove. With British summer time ending in a couple of days sooner than you think§, now is as good a time as any to prepare a stock for the winter.

Guess which are handmade ...

Guess which are handmade …

There are lots of suggested ‘recipes’ for these on the web. Many of these combine wax with pine cones, sometimes with the addition of a wick. By adding a few drops of essential oils to the melted wax you can create both an attractive and fragrant item to decorate your home.

Note I said “decorate your home”, not “light your wood burning stove”. Take it from me … they’re pretty hopeless as firelighters. Been there, sent a postcard. I’ve collected pine cones, dried them for weeks in the boiler room, wrapped a wick around them, dipped them in scented wax and been wholly unimpressed at how poor they are as firelighters.


Flamers …

Don’t bother.

Commercial firelighters for wood burning stoves are usually composed of a wax-dipped, twisted wood shavings. Flamers work very well. However, at £24 for 200 they’re not inexpensive – particularly for something that’s going to just sit next to the stove in a bowl and then, in the space of a few minutes, literally disappear in a ball of flame.

Roll your own

Elm bowl ...

Elm bowl …

You’ll need some wood shavings, egg boxes and molten beeswax. You can buy the coarsest animal bedding material or – better still – find a friendly wood-turner and ask them to save some of their discarded shavings (which will also work well in your smoker). Melt the beeswax in a slow cooker or Bain Marie. Stuff the wood shavings reasonably tightly into the wells of the egg box and dribble liberally with melted wax.

Job done.

If you want to make them slightly fragrant then add a few drops of juniper or patchouli essential oils to the melted wax before pouring it over the wood shavings. They’ll smell nice but they’ll still look rubbish.

Come on baby ...

Come on baby …

Tear and share

These are not the sort of things you’ll see featured in Homes and Gardens or Country Living. They are a triumph of function over form. Hide them away somewhere close to the stove. When needed, simply tear a ‘cell’ off the egg box, stack it onto the pile of kindling and logs (I’m an advocate of the ‘top down’ or Swiss style method of firelighting), light the blue touchpaper and retire to an armchair to enjoy the fire.

I claim no originality for this idea. There are loads of websites with similar suggestions, using everything from sawdust to the lint from a spin-dryer as the flammable material. Some of them look even worse than mine 😉

Ugly but fully functional ...

Ugly but fully functional …

This phrase is a bastardisation of the term form follows function originally used by the architect Louis Sullivan in an 1896 paper The Tall Office Building Artistically Considered. It became widely associated with modernist and industrial architectural design in the early 20th Century, essentially meaning that the shape of a building should reflect its primary purpose.

§ This post was written in the chilly early Spring with the intention of publishing it sometime in October (when BST ends). However, an extended period of travelling in late August and much of September meant I had to bring the date forward to post something vaguely useful (I hope) and  topical when I’d been doing no practical beekeeping for 3+ weeks. Coincidentally the date this appeared (22nd September 2017) is the autumn equinox … the date at which day and night are of approximate equal duration everywhere. About the time I’ll get the wood-burning stove going regularly.

 This phrase used to be the safety instructions on fireworks (and may still be for all I know) and became widely used as doing something incendiary. ‘Touchpaper’ was the paper fuse soaked in potassium or sodium nitrate.


Light my Fire was a 1967 song by The Doors that first appeared on their self-titled debut album.

But you knew that.

Counting Varroa

It’s that time of the season again. With the exception of readers in the Southern Hemisphere, Colonsay, the Isle of Man or a few favoured locations in the Highlands of Scotland, miticide treatments should be on to reduce Varroa levels.

For reasons explained elsewhere, it’s important that this is done before the winter bees are exposed to the smorgasbord of viruses that Varroa trasmits when it feeds.

It’s not sufficient to just treat. You also need to have some idea that the treatment is reducing the numbers of Varroa in the colony.

Counting by numbers

It has been determined that only 10-20% of mites in a colony are phoretic i.e. attached to emerged workers. The majority of treatments (MAQS is the current exception) only target these mites. Therefore, treatments are usually applied over a period of several weeks to ensure that mites newly emerged from capped cells are also exposed.

There are a couple of obvious ways to determine the mite load before and after treatment. These include:

  • conducting an alcohol wash test, or a sugar-roll equivalent, of workers to quantify the phoretic mites.
  • uncap a known amount of worker brood (drone brood is almost certainly absent from colonies this late in the season) to quantify mite infestation.

However, both are pretty intrusive and – with the exception of the sugar-roll – involve the sacrifice of bees or brood, so perhaps not ideal at this stage of the season. However these are the most accurate way of measuring things.

Counting the corpses

Out, damn'd mite ...

Out, damn’d mite …

Alternatively, and this is what most beekeepers do, apply the treatment and count the mite drop.

To count the mites you need some way of catching the mites. Open mesh floors (OMF) can easily be fitted with a sheet of closely-fitting (most usefully white) Correx onto which the mites drop. Restrict the access of ants and other creepy crawlies to the tray or they may steal some of the corpses. Check these on a regular basis during treatment and you have a simple way of determining whether the treatment is working.

The treatment may be working, but has it been effective?

The scores are on the floors

If you count thousands of dropped mites and that number doesn’t diminish during treatment i.e. the drop per day early and late in treatment is broadly similar, then the treatment is working, but it’s not effective or finished as there are loads of mites still left.

What you need to observe is a reduction in mite drop when comparing early and late counts.

Depending upon the treatment, the first days’ drop isn’t necessarily indicative of whether the miticide is working (or of the phoretic mite load of the colony). It may take a day or two for the treatment to achieve maximum kill. Vaporised oxalic acid often gives a better drop after 24-48 hours, and continues to work over about 5 days.

As indicated in the footnote, the numbers of brood emerging per day will expose ‘new’ mites to the miticide, increasing the count. If emerging brood levels vary, so will the mite drop … but also remember that the efficacy of the miticide also varies over time.

What you’re looking for is a hugely reduced count of mites dropped per day at the end of the full treatment period when compared with the beginning.

I usually carefully monitor the first week or two and the last week. Simples.

Objective vs. subjective counting

Easy counting ...

Easy counting …

Some beekeepers count each and every mite that appears on the trays. Others just look for ‘lots’ at the beginning and ‘almost none’ at the end. I consider >50/day is ‘lots’ and only count smaller numbers.

The less frequently you count the more difficult it is to discriminate dead mites from all the other detritus that accumulates on the trays. The cell cappings, the pollen that’s being dropped, the wax scales and various other bits of bee, all make spotting the mites more tricky.

The larger the area you’re counting the more likely it is to either double-count or miss mites. Make life a bit easier by ruling a simple grid onto the tray and counting square by square.

Scrape the tray clean after counting the mites … if you leave the tray dirty you’ll end up double counting and struggling to spot mites that are knee-deep in the crud that’s fallen through the OMF.

Don’t try this at home

Varroa are a pretty regular size and shape. And colour for that matter. At least adult mites are. This raises the possibility – though perhaps only to those with a tendency towards geekiness – to try and count mites automagically§.

Rather than stand around the apiary squinting through myopic eyes at tiny reddish ovals you could simply photograph the tray and then process the image later.

Been there, done that … or at least tried to.

Fiji ...

Fiji …

There’s a freely-available, well-supported, image analysis package called ImageJ (also distributed sometimes as the auto-referential Fiji … Fiji is just ImageJ). It’s possible to count objects using ImageJ having set criteria that define them.

As an exercise in near-futility I’ve attempted to do this for Varroa. You first need to ensure the Varroa are of a standardised size and shade by scaling the image appropriately and correcting the colour. This can be done by using a photographers grey card of a known size, placed to the side of the Varroa tray. You then use this as a reference to scale the image and define the white balance.

Finally, you define the size, roundness and shade of a Varroa and process the image in ImageJß. It counts the mites and provides an overlay with each identified mite numbered. You’re then able to check whether it’s missed any.

It does.

Consistently variable

This is the point I’ve got stuck at … the accuracy is all over the place but it’s clearly not impossible. Problems include:

  • It overlooks mites lying on their ‘edges’, perhaps propped up on a speck of pollen or fragment of wax. Better colour definition and a wider range of ‘ovality’ might sort this out.
  • It misses mites lying immediately next to another mite – these look like 8 or ∞ rather than a simple solid oval. I’ve no clear solution to this other than counting lower densities of mites.
  • It ignores some mites that appear as ‘doughnuts’ because of reflection from the shiny carapace. Don’t use flash for the photography.
  • It counts some ovalish, reddish lumps of pollen that are about the right size as mites. D’oh!

At best the accuracy is above 80%, but it’s variable. The lack of consistency is the major issue. If it was always 80% it would be perfectly acceptable and a very fast way to record mite numbers. At worst – usually when the tray is messy and mite numbers are relatively low – it’s well below 50%.

This is an intriguing beekeeping-related task for long winter nights. If you’re a geek. My ambition is to take a quick smartphone photo, scrape the Correx tray clean and then (automagically!) do the counting at home with a cup of tea and piece of cake.

I’ll keep persevering … particularly with the tea and cake 😉

† It’s currently Spring in the Souther Hemisphere, so the wrong time to treat. The remaining locations (and Australia) have no Varroa so have no need to treat. Lucky blighters.

‡ This is a gross oversimplification. Obviously, a broodless colony will only have phoretic mites. Swarms that issue from colonies take 35% of the mites with them, leaving 65% on the remaining bees (or capped in cells). The actual number of phoretic mites likely depends upon the prior history of egg laying by the queen. It also is probably influenced by the overall level of mites in the colony (or ratio of uncapped brood to mites perhaps). I’m not sure if anyone has modelled this successfully, though it might be possible to do this with BEEHAVE.

§ Automagically is pretty obviously a concatenation of automatic and magic. It is usually defined as “(especially in relation to the operation of a computer process) automatically and in a way that seems ingenious, inexplicable, or magical”. Interestingly, the term was first used in the 1940’s, well before the advent of computers.

ß Once I’ve got this working better I’ll provide some instructions … in the meantime the menus that you need to use are Analyse … Set Measurement and Analyse … Count Particles. Image scaling needs to be done first in ImageJ. Currently I do the white balance in Adobe Lightroom (which is overkill, but convenient as all my images go through this software).


Integrity …



… make sure your stored broods and supers have it. For that matter, your hives need it as well.

Early autumn is when wasps appear in droves. They gatecrash picnics and pester our bees as they search for carbohydrates. This year, after a pretty poor summer, they’re a bit later that usual … at least in this part of the UK. Queen wasps have now stopped rearing brood – which requires a protein-rich diet for the colony – and they’ve now switch to carb-bingeing.

My apiaries are away from my house, so the first thing I become aware of is the increased numbers of wasps investigating the stacked up piles of broods and supers. ‘Wet’ supers containing residual honey after extraction are very attractive to the wasps. They look for any structural weakness in the stack … a poorly fitting roof, a warped crownboard or gaps at the joints in the boxes.

If any of these provide access there will be a never-ending stream of wasps making return trips from their nest site – which may be up to a mile away – and the source of the honey. When you walk past the boxes you can sometimes hear the rustling or scratching of the wasps as they look for additional routes out once they’re laden with honey.

They can even chew through poly boxes where there’s a hint of  structural weakness to gain entry or subsequent exit from the pile. In the picture (above) the corner of the upper Swienty poly super – at the point where the hive tool had slightly indented the relatively soft polystyrene – was mercilessly attacked, leading to a neat chewed hole large enough to give the wasps access.

Structural integrity

Maintain neat stacks of equipment, securely sealed at the base and the top. Try and avoid having an open mesh floor at the bottom of the stack, even if the entrance is sealed up. The scent of honey will still attract wasps from far and wide … and once they’re there they are very persistent.

I use sheets of spare Correx or solid split boards with all the entrances closed up tightly on the bottom of the stack. If you don’t have anything suitable a sheet of thick polythene forms a reasonably impenetrable barrier – to scent and wasps.

If there are gaps, and there probably will be as equipment ages and warps or gets bashed about, seal up the gaps as soon as you notice them. Waterproof gaffer tape is as good as anything for this as a temporary fix.


It’s not only the integrity of empty stacks of equipment that is being tested at this time of the season. Wasps will show similar levels of interest in colonies of all sizes – from double-brood monsters bulging with bees to mini-nucs containing only a cupful of workers and a queen.

Life’s a lot easier for the colony if they only have a single entrance to defend. Check the joints and junctions between boxes and seal any up where wasps might gain access. This includes the – entirely unnecessary in my view – ventilation holes in the roof. Unless these have well-fitted mesh there’s a chance the jaspers can get in and from there to the honey supers if your crownboard also has another – entirely unnecessary – ventilation hole.

Kewl floor entrance slot

Kewl floor entrance slot

Life’s easier still for the colony if the entrance is small and/or easy to defend. The kewl floors I favour, with an “L-shaped” entrance tunnel, provide ample opportunity for the guard bees to challenge any inquisitive wasps – at the entrance per se, or where the tunnel opens into the brood box. I don’t think I’ve ever had to provide additional protection to full-sized colonies using one of these floors.

Unbalanced or nearly-colonies

Small colonies, recently created colonies or colonies that are otherwise weakened are a different matter altogether. In all of these the colony is either understrength or lacking a full complement of worker types.

Reduced entrance ...

Reduced entrance …

Or both.

For example, newly created nucs containing a late-mated queen and a couple of frames of brood and adhering bees, may well not be up to defending themselves properly against the determined attention of wasps (which is the only sort of attention wasps are capable of).

Mini-nucs or queenless colonies are particularly susceptible and regularly succumb to attacks by wasps.

Maximise the opportunities these colonies have to defend themselves by restricting the entrance to a very narrow gap. The gaping maw of Thorne’s Everynucs definitely needs reduction, either by closing off 80% of it with grass stuffed into the gap (in an emergency) or using foam or Varroa mesh offcuts to achieve the same end.

Don’t be sloppy

Slopping large quantities of sugar-rich syrup about the apiary is a sure-fire way to attract the striped hordes. Make sure feeders are watertight (syrup-tight) and don’t leak. Pour carefully and mop up any spills that do occur.

I almost exclusively use fondant for late-season feeding. Spills are non-existent. The block is cut in half with a spade (or breadknife) and placed inverted on top of the colony. It takes seconds and works well. As an aside, you can feed fondant and treat with Apiguard at the same time – I’ve been asked about this recently.

Don’t leave offcuts of brace comb lying about in the apiary. Tidy up after you, don’t conduct unnecessary inspections or leave unattended frames propped up against the hive stand while you slowly go though a colony.

All of the above help the colonies avoid the attention of wasps … they also reduce the likelihood of colonies being robbed out by other bees, a topic I’ve mentioned before and will discuss in the future as it has very significant implications for disease transmission.

† Jasper is a slang name for wasps I was aware of as a boy in North London. The origin of the term appears unknown, but QI has an interesting discussion on it. It’s variously ascribed to Dorset, Lincolnshire (East Midlands), Yorkshire and Glasgow. It’s also not clear the derivation of the word … ‘jasper’ sounds like the genus Vespa which our common wasps belong to. Alternatively, there’s a striped mineral called Jasper which (potentially, though not to me) resembles the striped abdomen of wasps.

That’s all folks

That's all Folks

That’s all Folks

It’s late August and the end of my least successful beekeeping year ever. That sounds very negative, so perhaps it should be qualified. It’s the end of my least successful beekeeping year in terms of honey production.

However, in terms of the satisfaction I’ve got from my beekeeping, it’s been a pretty good year. Let’s examine these two things separately, dealing with the bad news first.

Tell ’em about the honey, mummy

My production colonies only generated about 25lb each of Spring honey. Some of this was clearly oil seed rape (OSR) as there were fields just about in range, but much of it was essentially mixed hedgerow and tree nectar, and none the worse for that. This was all extracted in late May or early June and is now stored, set, in buckets. Later in the year, once the temperature drops, I’ll prepare soft set honey for sale or distribution to friends and family.

25lb is firmly at the bottom end of the averages over the last few years though – in fairness – It’s only my second Fife Spring, so I don’t have much recently to compare it with. Colonies were doing well when I first inspected them, but in some cases that wasn’t until early May. The active beekeeping season is only 4-5 months long here (latitude 56.3° N).

June started well, with clear weather and high temperatures.

And then it started to rain. And continued for almost the entire month.

Lime can yield well in July

Lime can yield well in July …

None of my full-size colonies needed feeding, but most reduced their brood rearing. July nectar flows were poor. The lime yielded a small amount of very high quality honey, but for whatever reason – poor weather, colonies not strong enough, patchy flows – pretty-much nothing else. The summer honey was extracted in mid-August and is already disappearing fast.

I didn’t take any colonies to the heather as I was abroad for a chunk of July when I’d need to be preparing and shifting them to the moors. And, in all likelihood, they probably weren’t strong enough anyway.

And that was it … like last year, all over much sooner than expected.

There’s some balsam in central Fife along the River Eden that might give some late-season nectar and there’s ivy (but that is some way off flowering yet) but I usually let the bees keep anything they collect once the summer honey is extracted.

Flowering ivy

Flowering ivy

And the good news is

Beekeeping isn’t all about honey. There’s also tremendous satisfaction to be gained from working with the colonies, improving your stock and feeling that – although perhaps not in complete control – you’ve got a pretty good grasp of what’s happening and how things are going.

In this regard, 2017 was a success.

I know I lost one swarm (actually a cast from the queenless half of a split). I got a call to say that the apiary was thick with bees but they’d long gone by the time I extricated myself from meetings and got home. In itself this wasn’t a success. However, I learned my lesson and managed to hive a second cast that issued from the same colony a day or two later. I also had success with my bait hives.

With a couple of exceptions my vertical splits went well, with the resultant queens both laying well and heading well-behaved colonies. The couple that didn’t work developed into (drone) laying workers and were dealt with successfully by uniting.

In retrospect, considering the weather in early/mid-June I’m astounded any queens managed to get out and mate. By late July colonies headed by these newly mated queens were developing well, with frame after frame of brood exhibiting a pretty respectable laying pattern.

That'll do nicely

That’ll do nicely …

Throughout the season I had a pretty good idea what was happening in most of my colonies. There were no big surprises … “Oops, a virgin queen, where did she come from?”, or “Grrrr … no queen, no eggs and no swarm cells, I’m stumped”.

Colonies behaved in a thoroughly predictable manner. Strong ones were caught before they swarmed, split and were merged back to a double brood box. Nucs developed pretty well, though they needed close attention and some emergency feeding through June. No drama, no panic.

The end of the summer season, other than the truly woeful honey yield, has left me with a good number of nicely behaved and generally very strong colonies. As always there’s one exception, but I’ll unite that weakling late this week if things haven’t picked up.

All the gear, no some idea

Split board ...

Split board …

Gradually equipment standardisation is starting to pay dividends. I ran out of almost nothing (I certainly didn’t run out of supers 🙁 ) and managed to mix’n’match as needed to leave colonies secure, watertight and with the proper bee space when needed. Homemade split boards ended up being pressed into service as floors and it’s clear I’ll have to make some additional kewl floors this winter.

Bamboo-strengthened foundationless frames were a great success. Furthermore, I prepared a second batch mid-season and never got round to using them, so have plenty to start the season next year. Result! However, it’s sobering to realise that one of the reasons they weren’t used was that the nectar flow simply wasn’t strong enough to get them drawn properly.

Finally, whilst we’re on the subject of equipment, I’ve used about half a dozen Abelo poly hives this year in addition to the usual Swienty boxes with homemade floors and roofs. First impressions of the Abelo boxes are pretty positive and I’ll write something up later in the year on them.

Season’s end … or the start of the new season?

Late summer and autumn is an important time in the beekeeping year. Some even consider it the start of the next season, as success in the subsequent year is very dependent upon the preparation in the preceding autumn.

Feed'n'treat ...

Feed’n’treat …

All my colonies are scarfing down large quantities of fondant at the moment. They’ll all get another few kilograms as the autumn progresses. Unless there’s good reason to, it’s unlikely any colonies will be inspected again until Spring.

Varroa treatment is ongoing and the mite drop from most colonies is reassuringly low. I count the mites from each colony over a two week period. Over the first 5 days, some dropped just single figures …

All colonies are coordinately treated to maximise decimation of the mite population at a time when bees have a tendency to drift more and/or rob adjacent colonies – both being well-documented routes by which Varroa can be transmitted between hives. I’ve also helped a neighbouring beekeeper (with colonies within range of my own apiary) by loaning out my Sublimox so that, together, the mite population at a landscape-scale is reduced.

This is simple common sense. I don’t want my (nearly) mite-free colonies infested from neighbouring apiaries and I also don’t want the colonies I do have with appreciable mite levels (~50+ after 5 days treatment) to infest others.


It’s far too soon for much serious thought about 2018. However, I already know there are going to be some major changes to my beekeeping. The local Council have just announced that they will shortly (Spring next year) build a new road literally through the middle of my bee shed and apiary … finding a new location and getting things rebuilt is my major focus at the moment.

And finally … it’s harvest time and raining again …

Mainly dry ...

Mainly dry …

† Tell ’em about the honey, mummy was a catchphrase from a TV advert for Sugar Puffs breakfast cereal. The advert aired from 1976 to ’85 and featured the Honey Monster and Henry McGee (from the Benny Hill show).

Henry is the one on the right.

They don’t make advertising like that any longer. For obvious reasons.

‡ Scarf is American slang meaning to ‘eat voraciously’. It’s probably a bastardisation of the word scoff. Scarf has other meanings and I strongly suggest you don’t look these up.


That's All Folks

That’s All Folks

The phrase That’s all folks dates back to 1930 when it was used on the closing screen of a Warner Bros. Looney Tune cartoon.

Over the years many different characters used this line on both Looney Tunes and Merrie Melodies cartoons. Mel Blanc (1908-’89), the actor who voiced (stuttered) the most famous version … Th-th-th-that’s all folks! has the engraving That’s All Folks on his gravestone.

There’s a 1949 Merrie Melodies cartoon called The Bee-Deviled Bruin with the Three Bears, a colony of bees and a shortage of honey for breakfast. Typical slapstick ensues. It ends with That’s all folks”.

Right here, right now

In February 2016 I posted an article on When to treat colonies with miticides. It was read by subscribers, generated a bit of discussion – in particular on Apiguard use – and then disappeared into the howling wilderness that is the interwebs …

Google hides the searches that drives most of the website traffic to this site. However, it has been found … as is clear from the access stats (below), it is now being accessed extensively.

This reflects the change in the seasons as beekeepers turn their thoughts from harvesting honey to protecting their colonies from the ravages of Varroa and the viruses it transmits.

'When to treat' stats ...

‘When to treat’ stats …

It’s worth reiterating it here, though this won’t be news to regular readers, Varroa itself is probably not the problem. The problem is the smorgasbord of viruses that Varroa transmits when feeding on the haemolymph (blood) of honey bee pupae.

Benign and virulent

Most important of these viruses is deformed wing virus (DWV). This virus has a sort of Jekyll and Hyde personality. It’s probably present in all honey bees, transmitted between bees while larvae are being reared and during trophylaxis (the regurgitation of liquid food between bees). Under these conditions, and in the absence of Varroa the virus is probably benign.

DWV symptoms

DWV symptoms

Of course, it’s difficult to test whether it is really benign as there probably aren’t any bees that lack DWV. Even bees that have never been exposed to Varroa, such as the black bees on Colonsay, have DWV. Let’s assume that, even if not benign, it has minimal detrimental effect on the bees.

Varroa changes the route by which DWV is transmitted. Instead of being orally transferred – a route the bees have probably evolved to cope with – Varroa bypasses any defence mechanisms by ‘injecting’ DWV directly into the blood. Under these conditions DWV reproduces rampantly – for reasons that have yet to be determined – causing the ‘deformed wing’ symptoms most beekeepers are familiar with.

Symptomatic adult, or recently emerged, bees can contribute little or nothing to the colony.

Live fast, die young

But there’s more bad news. Asymptomatic adult bees with high levels of DWV have a shorter lifespan and die prematurely. This is perhaps not an issue during the heady days of summer when the turnover of worker bees is at its height – the queen is laying well, perhaps 1500-2000 eggs per day, the colony is bulging and individual workers “live fast and die young” after about 6 weeks.

Formally, I don’t think it’s been shown that mid-season workers have a shorter life span when they have high levels of DWV. What is known, and what is much more important, is that winter bees die prematurely if their DWV levels are high.

Winter bees are the ones with high levels of fat in their bodies. These are the bees that get the colony through the winter. Some might live for 5-6 months in the UK, and it’s known they can live for up to 9 months. If these bees die early, in the absence of any significant brood rearing, the colony dwindles and dies.

Game over.

Preventing the inevitable

Varroa transmits DWV and results in high levels of DWV. High levels of DWV in winter bees shortens their lifespan and results in colony losses. How can you prevent the inevitable?

In the absence of ways to directly control DWV levels (these are in development but you’re then tackling the symptom, not the cause) the only way to do this is to prevent the transmission of DWV to the winter bees by Varroa in the first place.

And you do this by applying effective miticides early enough that the winter bees are protected from exposure to Varroa, and the viruses it transmits.

How early is early?

I discussed this in the earlier article and am working on a more nuanced version at the moment. Essentially – and I’m writing this in mid-August – the answer is now or very soon.

In the definitive publication demonstrating the premature death of winter bees by DWV, Peter Neumann and colleagues detected a measurable reduction in longevity as early as November in the colonies they studied. These bees were age-marked and had emerged 50 days earlier. The eggs had therefore been laid in the first week of September … and been capped (together with any Varroa) as pupae in mid-September.

Therefore, treatments to reduce Varroa should be completed by mid-September to protect the winter bees. Since many treatments take ~4 weeks the time to treat is right now.


There’s climatic variation between parts of the UK and Bern, where the study by Peter Neumann was conducted. There’s also seasonal variation year on year.

In the balmy South the dates will be later than in the frigid North. In cool years with an early autumn they will be earlier, whereas an Indian summer will delay the need to treat.

Treatments are generally incompatible with a honey flow. If you take your bees to the heather you have to balance collecting a late heather crop with protecting the bees from the ravages of Varroa.

it’s not possible, or wise, to be dogmatic about precise dates … other than to say that miticide treatment is generally required earlier than you think to protect the winter bees from DWV.

Better late than never?

Well, yes, but the damage may well have been done.

The annual survey of beekeepers in Scotland regularly includes significant numbers using Apiguard in October. Close, but no cigar (actually, not even close) … it’s probably too late to reduce Varroa levels in a meaningful way, and it’s unlikely to be effective anyway as Apiguard needs average temperatures around 15°C.

All of the comments above on the timing of treatment make the assumption that the treatment is effective – the right dose, the right duration, the absence of resistance etc.

Finally, it’s worth noting that starting treatment in mid/late August does not reduce Varroa levels to the lowest achievable levels. Treating later in the year does this, because more mites are phoretic and ‘reachable’ by the treatment. To reduce mite levels to the minimum you also have to also treat midwinter … something for another post.

† Live fast, die young was the title of a biography of the actor James Dean by James Gilmore. It’s a popular phrase, being used for a movie and several song titles. The extended version Live fast, die young and have a good looking corpse, often wrongly attributed to James Dean, actually came from the 1947 book Knock on Any Door by Willard Motley.

‡ Close but no cigar is a mid-20 phrase from the USA. It dates back to the time when fairground stalls gave out cigars as prizes.


Right here, right now is a song released in April ’99 by Fatboy Slim (Norman Cook) from the album You’ve come a long way, baby‘. If you appreciate evolution you’ll enjoy the video …

… but you’ll need to like beat/dance music to appreciate the track.

Extrapolating Asian Hornets

Extrapolation in mathematical terms means “the extension of a graph, curve, or range of values by inferring unknown values from trends in the known data”. There’s a rather poor scientific joke which involves ‘extrapolating the line’ from a single data point.

Here’s the same joke from the incomparable

Extrapolating (with thanks to

… which brings us neatly to the Asian hornet (Vespa velutina). This invasive species predates honey bees and other pollinators and is a threat to beekeeping for two reasons:

  • by killing honey bees (which comprise > 50% of the diet) it can destroy colonies
  • by hunting at hive entrances it prevents bees from foraging, so reducing honey yields
Vespa velutina

Vespa velutina …

As many will be aware, at those who members of a beekeeping association or internet-savvy, an Asian hornet nest was discovered in Tetbury, near Bristol, in September 2016. Although the nest was destroyed (and other nests were not found) there remains the concern that the Asian hornet may be established here. If that’s the case, or if when it arrives again, how far and how fast will it spread in the UK?

A recent publication by Matt Keeling and colleagues has attempted to to address this. You’ll appreciate the relevance of the cartoon above … August 2016, no hornet nests, September 2016, one hornet nest. How many can we expect in the future?

A long way from home

Asian hornet distribution ...

Asian hornet distribution …

Unsurprisingly (the clue is in the name) the Asian hornet comes from Asia. The native distribution includes tropical South East Asia where it exists in a number of different colour morphs or sub-species. However, it spreads – naturally on its own and with the inadvertent help of man – and is now established in Korea, Japan and North West Europe.

The Asian Hornet appeared in South West France in 2004. It was thought that overwintering queens were imported with a shipment of pottery from China (it is the V. velutina nigrithorax subspecies – see map for native distribution). Since 2004 the Asian hornet has spread widely across France, Spain, Belgium, Portugal and Italy. You can view a dynamic Google map showing location and time of detection here.

It’s a short hop across the Channel from Northern France for an insect that flies strongly and disperses widely, so there was every expectation that the Asian hornet would appear in the UK in due course. Remember that bluetongue virus of sheep was introduced to the UK in 2006 by tiny Culicoides midges wafted across the Channel on the prevailing South Easterly winds.

Brexit or not, the Asian hornet can easily get to Southern England.

Closer to home

Asian hornets were first found in Tetbury, Gloucestershire, in September 2016 and subsequently in North Somerset. A nest was found in Tetbury and destroyed. Haplotype analysis demonstrated that, unsurprisingly, the hornets were related to those in Northern France. Worryingly, this analysis also demonstrated that the hornets were related, but no closer than at the grandparent level.

This suggests one of two scenarios. Either there were two separate incursions from France by hornets that were closely related or the Asian hornet was established in the UK before 2016 and the Somerset and Gloucestershire finds represent progeny (two generations later) of this initial invasion.

There have been no further reported Asian hornet finds on the mainland (as of early August 2017 and remembering that absence of evidence doesn’t mean evidence of absence) though additional nests have been found on Jersey and it’s possible that the hornet is established in the Channel Islands.

How far, how fast?

Whether or not the Tetbury hornet incursion has been contained there remains the question about how far and fast will the Asian hornet spread in the UK.

This is the sort of thing that can be modelled by epidemiologists. Taking account of a variety of factors such as the numbers of queens produced per nest, the environmental suitability for the hornet, the dispersal distances and – importantly for a species originating in tropical regions – the latitude (and hence temperature).

Much of the real numbers for these various factors come from studies of the spread of the Asian hornet in France. For example, the mean dispersal distance of new queens is about 18 miles i.e. Tetbury to central London in about 5 generations.

Predicted spread of the Asian hornet in UK …

In the figure above A-D are the early years (<5), E and F are the predictions for 10 and 20 years hence. Remember, this is an inexact science as the predictions are being made from a very small founder population. G shows the confidence limits which, at 90% (the palest shading) are very broad.

Is Scotland safe?

As a beekeeper in Scotland the potential to spread North is a concern … those of you living further South can simply jump ahead to the conclusions.

A key feature of the prediction Keeling and colleagues made was that increasing latitudes (and possibly altitude going by the pale shading of North Wales and the Pennines, though this could also be lack of suitable nesting environments – the Asian hornet prefers oak trees apparently) will restrict breeding success and hence spread due to reduced temperatures.

They modelled this by assuming reproductive success/spread (actually queens/nest) was 100% in Andernos-les-Bains, France (where much of the data used for the modelling was derived) and 0% in the North of England. This mirrors the situation for the European hornet which is much less common in Northern England. Assuming a linear decrease in queens per nest over this distance they reproductive success in Tetbury is only 38% that in Andernos-les-Bains. 

With these assumptions, Scotland is safe. I should add that I’m talking about natural distribution and spread. A single Asian hornet was discovered at a “retail warehouse in the central belt of Scotland” in March 2017. Although there’s no further official news about this discovery it seems likely it was imported ‘on the back of a lorry’ (and the SASA/NBU people will be able to tell where from after genetic analysis) to one of the giant distribution warehouses in Motherwell or Livingston. If the assumptions made about reproductive success at increasing latitudes are correct, this type of introduction is unlikely to result in the Asian hornet getting established in Scotland.

All of the modelling discussed so far assumes no intervention by FERA or by protective and vigilant beekeepers. The impact of nest destruction will be discussed in the future … but don’t get your hopes up 😉


Asian hornet nest

Asian hornet nest …

With only one (or two?) incursions and no further reports in 2017 it’s possible that the Asian hornet is yet to become established in mainland UK. Once here – and I think it’s pretty certain it will get here and become established – the speed with which it spreads may look like the model proposed here. If the underlying assumptions on reproductive success, dispersal distance etc. are representative of the situation in the UK then – without effective intervention – we can expect it to be widespread within a couple of decades.

However, a feature of all epidemiological modelling is that they are subject to revision and reinterpretation … inevitably leading to further publications.


STOP PRESS and related …

Asian hornet isolation confirmed in Woolacombe, North Devon, late September 2017

Full analysis of 2016 isolates published in PLoS One. Budge GE, Hodgetts J, Jones EP, Ostojá-Starzewski JC, Hall J, Tomkies V, et al. (2017) The invasion, provenance and diversity of Vespa velutina Lepeletier (Hymenoptera: Vespidae) in Great Britain. PLoS ONE 12: e0185172.

† Don’t mistake the Asian or Yellow-legged hornet (Vespa velutina) with the Asian giant hornet (Vespa bloodyenormousandterrifying). The latter has a wingspan of 7.5cm and its proper scientific name is Vespa mandarinia. A number of newspaper articles in autumn 2016 made this mistake. Many also chose to use images of the European hornet (Vespa crabro) or other large stingy-looking insects … none of which are likely to help the public correctly identify the invasive Asian hornet.

Vespa mandarinia

Vespa mandarinia …