Tag Archives: DWV

The day job

It’s no secret that I have both amateur and professional interests in bees, bee health and beekeeping.

During the weekend I sweat profusely in my beesuit, rushing between my apiaries in Central and Eastern Fife, checking my colonies – about 15 at the autumn census this year – averting swarms, setting up bait hives, queen rearing and carrying bulging supers back for extraction.

Actually, not so much of the latter in 2017¬† ūüôĀ ¬†I did get very wet though, much like all the other beekeepers in Fife.

The BSRC labs

The BSRC labs …

During the week I sit in front of a large computer screen running (or sometimes running to keep up with) a team of researchers studying the biology of viruses in the Biomedical Sciences Research Complex (BSRC) at the University of St. Andrews. Some of these researchers work on the biology and control of honey bee viruses.

During the winter the beekeeping stops, but the research continues unabated. The apiary visits are replaced with trips in the evenings and weekends to beekeeping associations and conventions to talk about our research … or sometimes to talk about beekeeping.

Or both.

This weekend I’m delighted to be speaking at the South Devon Beekeepers Convention in Totnes on the science that underpins rational and practical¬†Varroa¬†control.

Which came first?

I’ve been a virologist my entire academic career, but I’ve only worked on honey bee viruses for about 6 years. I’ve been a beekeeper for about a decade, so the beekeeping preceded working on the viruses of bees.

However, the two are inextricably entwined. Having a reasonable amount of beekeeping experience provides a unique insight into the problems and practicalities of controlling the virus diseases that bees get.

Being able to “talk beekeeping” with beekeepers has been very useful – both for the communication of our results to a wider audience and in influencing the way we approach our research.

Increasingly, the latter is important. Researchers need to address relevant questions, using their detailed understanding of the science to deliver practical solutions to problems1. There’s no point in coming up with a solution if there’s no way it’s implementation is compatible with beekeeping.

Deformed wing virus

DWV symptoms

DWV symptoms

The most important virus for most beekeepers in most years is deformed wing virus (DWV). This virus¬†“does what it says on the tin”¬†because, at high levels, it causes developmental defects in pupae that emerge with shrivelled, stunted wings. There are additional developmental defects which are slightly less obvious, but there are additional (largely invisible) changes which are of greater importance.

DWV reduces the lifespan of worker bees. This is probably not hugely significant in workers destined to live only a few weeks in midsummer. However, the winter bees that get the colony through from September through to March must live for months, not weeks. If these bees are heavily infected with DWV they die at a faster rate. Consequently, the colony dwindles and dies out in midwinter or early Spring. At best, it staggers through to March and then never builds up properly. It’s still effectively a winter loss.

Our research focuses on how¬†Varroa influences the virus population. There’s very good evidence now that DWV transmission by¬†Varroa leads to a significant increase in the¬†amount of virus, and a considerable¬†decrease in the diversity of the virus population.

So what?

Well, this is important because if we want to control the virus (i.e. to¬†reduce DWV-associated disease and colony losses)¬†it must help to know the proper identity of the virus we are trying to control. It will also help us¬†measure how well our control works. We know we’re measuring the right thing.

We’re working with researchers around the world to define the important characteristics of DWV strains that cause disease and, closer to home, with entire beekeeping associations to investigate practical strategies to improve colony health.

Chronic bee paralysis virus

CBPV symptoms

CBPV symptoms

We’re about to start a large collaborative project on the biology and control of chronic bee paralysis virus (CBPV). This virus is becoming a significant problem for many beekeepers and is increasing globally. It’s a particular problem for some bee farmers.

CBPV causes characteristic symptoms of dark, hairless, oily-looking bees that sometimes shiver, dying in large smelly piles at the hive entrance. It typically affects very strong colonies in the middle of the season. It can be devastating. Hives that should be the most productive ones in the apiary fail catastrophically.

Why is a virus we’ve known about for decades apparently increasing in the amount of disease it causes? Are there new virulent strains of the virus circulating? Are there particular beekeeping practices that facilitate it’s spread? We’re working with collaborators in the University of Newcastle to try and address these and related questions.

I’ll write more about CBPV over the next year or so. It won’t be a running dialogue on the research (which would be crushingly dull for most readers), but will provide some background information on what is a really fascinating virus.

At least to a virologist ūüėČ

And perhaps to beekeepers.

Grow your own

As virologists, we approach the disease by studying the virus. Although we maintain an excellent research apiary, we don’t do many experiments in ‘the field’. Almost all the work is done in test tubes in incubators in the laboratory … or in bees we rear in those incubators.

Grow your own

Grow your own …

We can harvest day-old larvae (or even eggs) from a colony and rear them to emergence as adult bees in small plastic dishes in the laboratory. We use an artificial diet of sugar and pollen to do this. It’s time consuming – they need very regular feeding – but it provides a tightly controllable environment in which to do experiments.

Since we can rear the bees, we can therefore easily test the ability of viruses to replicate in the bees. Do all strains of the virus replicate equally well? Do some strains outcompete others? Does the route by which the virus is acquired influence the location(s) in the bee in which the virus replicates? Or the strains it is susceptible to? Or the level of virus that accumulates?

And if our competitors are reading this, the answer to most of those questions is ‘yes’ ūüėČ

We can even ask questions about why and how DWV causes deformed wings.

Again, so what? We suspect that DWV causes deformed wings because it stops the expression of a gene in the bee that’s needed to make ‘good’ wings. If we can identify that gene we might be able to investigate different strains of honey bee for variation in the gene that would render them less susceptible to being ‘turned off’ by DWV. That might be the basis for a selective breeding project.

It’s a simplistic explanation, but it’s this type of molecular interaction that explains susceptibility to a wide range of human, animal and plant diseases.

Bee observant

Bee health is important, and not fundamentally difficult to achieve. There are some basics to attend to … strong hives, good forage, good apiary hygiene etc. However, it primarily requires good powers of observation – does something look odd? Are there lots of mites present? How does the brood look?

If things aren’t right – and often deducing this means comparisons must be made between hives – then many interventions are relatively straightforward.

Not long for this world ...

Not long for this world …

The most widespread problems (though, interestingly, this doesn’t apply to CBPV) are due to high levels of¬†Varroa infestation. There are effective and relatively inexpensive ways to treat these … if they’re used properly.

More correctly, they’re relatively inexpensive whether they’re used properly or not. However, they’re pretty ineffective if not used properly ūüėČ

Regular checks, good record keeping, comparisons between hives and informed observation are what is needed. Don’t just look, instead look for specific things. Can you see bees with overt symptoms of DWV? Are there bees with¬†Varroa riding around on their backs? The photo above has both of these in plain view. Are some hairless bees staggering around the top bars with glossy abdomens, or clinging to the side bars shaking and twitching?

Don’t wait, act

I’ve no doubt that scientists will be able to develop novel treatments to control or prevent virus infections of bees. I would say that … I’m a scientist ūüėČ ¬†However, I’m not sure beekeepers will be able to afford them, or perhaps even want to use them, or that they’d be compatible with honey production or of any use in Warr√© hives¬†etc.

I’m also not sure how soon these sorts of treatments might become available … so don’t wait.

If there are signs of obvious DWV infection you need to do something. ‘Obvious’ because DWV is always present, but it’s usually harmless or at least tolerated by the bees. My lab have looked at thousands of bees and have yet to find one without detectable levels of DWV. However, healthy bees have only about 1/10,000 the level of DWV present in sick bees … and these are the ones that have obvious symptoms.

I’ve discussed¬†Varroa control elsewhere, and will again.

Unfortunately, if your colony has signs of CBPV disease then Varroa control is not really relevant. The virus is transmitted from bee to bee by direct contact. This probably accounts for the appearance of the disease primarily in very strong colonies.

At the moment there’s little you can do to ‘cure’ a CBPV-afflicted colony. I hope, in 2-3 years we will have a better idea on what interventions might work. We have lots of ideas, but there are a lot of basic questions to be addressed before we can test them.

Field work

Field work

Business and pleasure

The half of my lab that don’t work on bee viruses study fundamental mechanisms of virus replication and evolution. They do this using human viruses, some of which are distant relatives of DWV. They work on human viruses as it’s only these that have excellent model systems to facilitate the types of elegant experiments we try to do. They’re also relatively easy to justify in funding applications, and it allows us to tap into a much bigger pot for funding opportunities (human health R&D costs probably total ¬£2 billion/annum, bees might be ¬£2 million/annum).

And no, my lab don’t get anything like that much per year for our research!

Importantly, the two activities on human and honey bee viruses are related. Our experience with the human viruses related to DWV made us well-qualified to tackle the bee virus. They replicate and evolve in very similar ways, we quantify them in the same way and there may be similarities in some ways we could approach to control them.

And with the bee viruses I can mix business with pleasure. If I’m going to the apiary I’ll get to see and handle bees, despite it being officially “work”. It doesn’t happen as much as I’d like as I’m usually sat behind the computer and all of the ‘bee team’ have been trained to work with bees by the ESBA.

However, at least when I talk to collaborators or to the beekeeping groups we’re fortunate to be working with we – inevitably – talk about bees.

And that’s fun¬† ūüėÄ


1¬†Several years ago I delivered an enthusiastic and rather science-heavy talk at a Bee Farmers Association meeting. I thought it had gone reasonably well and they were kind enough to say some nice things to me … and then I got the question from the back of the room which went something like¬†“That’s all very well young man … but what have you made NOW that I can put into my hives to make them healthy?”.

I’m sure my answer was a bit woolly. These days the presentation would have had a bit less science and bit more justification. We’ve also made some progress and it’s possible to now discuss practical strategies to rationally control viruses in the hive. It’s not rocket science … though some of the science it’s based on is reasonably fancy.

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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 Р2 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¬ß.

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 Р£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 …


‚Ƭ†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.

‚Ä°¬†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.

¬ß¬†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

Peaceful easy feeling

The 6-8 week period between late June and harvesting the summer honey is a quiet period in the beekeeping calendar. At least, it is in mine. My colonies aren’t going to the heather, so there’s nothing to prepare for that. Swarm control is complete and many colonies are now headed by new queens, so the chance of swarming is minimal.¬†The spring honey – what little there was of it on account of the incessant rain – was extracted in late June. It’s now easy going until the summer honey is taken off and the colonies are prepared for winter.

Inspect, or just observe?

The 7 day cycle of inspections that are so important as the season builds up become much less critical. If there’s a new mated, laying queen in a box with ample space, sufficient supers and enough stores (for adverse periods of weather) there’s actually little to be achieved by rummaging through the box on a weekly basis.

Instead, I generally just observe things from the outside. If pollen is being taken in by foragers, if there are good numbers of bees on orientation flights during warm mornings and if the hive is reassuringly heavy, then there’s probably no need to inspect weekly. A peek through a perspex crownboard can give a pretty good idea of how much space the colony has and whether they’re fully utilising the super. With experience,¬†hefting the hive (gently lifting the back an inch or two and judging the weight) is a good indication of whether they might need an additional super. And that’s it … I generally leave these strong, healthy colonies to simply get on with things during July and into August.

But inspect when appropriate

Of course, some hives will need checking. For example, any hives that are clearly below-strength for an unknown reason should be carefully checked for signs of disease. Varroa levels can be readily, albeit pretty inaccurately, determined by putting a Correx Varroa tray below the open mesh floor and the colony should be inspected for obvious signs of deformed wing virus (DWV) symptoms.

High levels of DWV

High levels of DWV …

If there’s any doubt about the health of the colony consult a good book on the subject (Ted Hooper’s¬†Bees and Honey is a reasonable start though some of the more comprehensively illustrated newer books might be better), ask your mentor or an experienced local association beekeeper and contact the local bee inspector if necessary.

Chronic Bee Paralysis Virus (CBPV) is a high-season problem for big, strong colonies. Sick bees exhibit characteristic shaking or shivering symptoms, look oily or greasy and accumulate in a large smelly pile below the hive entrance. A very distressing sight. I’ll be discussing CBPV in more detail over the next few months as it appears to be an increasing problem.

Queen problems

The other colonies I keep a close eye on are those with known or potential queen problems. These include colonies where the queen may not have mated, or those in which the queen appears to have got mated but the colony shows signs of early supercedure, suggesting that all is not right.

Hopalong Cassidy ...

Hopalong Cassidy …

The queen in the (rather poor) photograph above has a paralysed left rear leg. She’s a 2017 queen and emerged in early/mid June during a period of very poor weather. I found her as a skittish virgin very soon after emergence (quite possibly the day of emergence) then left the colony to get on with things. She was mated by the first week in July. Eggs were present but I didn’t see her in the colony. However, she wasn’t laying particularly well, either in terms of number or pattern.

Since I was disappearing to Malaysia on business for 10 days in late July I thoroughly inspected the colony before leaving. I discovered her hobbling around the frame, clearly with very severely impaired abilities. There was very little open or sealed brood in the colony. In the several minutes I watched her she didn’t lay any eggs despite checking lots of cells that looked polished and ready to me (but I accept she’s probably a better judge of a suitable cell than I am). She clearly¬†could lay, and you can see an egg at the tip of her abdomen. I suspect that, although her walking wasn’t grossly impaired, she was unable to properly ‘reverse’ into the cell.

Not a bee ...

Not a bee …

Don’t delay, act today

Mid-July, a strongish colony with almost no brood, a crippled queen and no means of checking things for a fortnight meant that prompt action was needed. I removed the queen and united the colony over the top of another strong colony. The alternative was to wait and see if the colony disposed of her, or tried to supercede her. Either would have imposed a delay of about a month after my return, there were limited numbers of larvae for the colony to start from, a rapidly ageing worker population and little chance of the colony building up strongly through the autumn to overwinter successfully. This was a case of using them or potentially losing them.

I’ve no idea how the queen came to have a gammy‚Ć leg. I’d not seen her since she’d been mated. One possibility is that two queens emerged at or near the same time, duelled in the hive leaving one dead and the other partially crippled. Although damaged, the queen still managed to leave the hive to mate successfully, but then struggled to lay properly.

We’ll never know.

Late evening

Finally, if you’ve not visited your apiary late on a warm, calm summer evening then you really should. Strong colonies can be heard from some distance away, a sort of low humming sound. There’s the heady smell of warm honey in the air as they evaporate off water from stored nectar in preparation for capping stores off for the winter ahead. Highly recommended.


‚Ƭ†Gammy meaning¬†(especially of a leg) unable to function normally because of injury or chronic pain … in contrast to the fictional cowboy Hopalong Cassidy used to label the image. Hopalong Cassidy had a wooden leg.

Colophon

Peaceful easy feeling was the title of a song by the Eagles released in 1972 on their debut album (Eagles). The band, or what’s left of them after the recent death of Glenn Frey, continue to play live with four concerts last month.

Don Henley has just turned 70 and should really Take it Easy ūüėČ

Apistan resistance

Apistan

Apistan

In an earlier article I discussed what Apistan is Рa pyrethroid miticide Рand the consequences of using it. These include decimation of the mite population if it is susceptible, coupled with the accumulation of long lasting residues in wax. These residues may adversely effect queen and drone development. I also discussed ways to avoid build-up of Apistan residues in comb.

The key phrase in the paragraph above is ‘if it is susceptible’. Unfortunately, resistance to Apistan and the related tau-fluvalinates develops very quickly. To understand why we’ll need to look in a little more detail at how Apistan and other pyrethroids work.

How does Apistan work?

Apistan, like other pyrethroids, works by blocking the activity of voltage gated sodium channels (VGSC) resulting in paralysis because the axonal membrane cannot repolarise.

What on earth does that mean?

Action potential

Action potential

Nerve transmissions – like the signal from the¬†Varroa brain to tell the¬†Varroa legs to move – travel along axons. These are usually very long thin cells. In the adjacent image¬†the ‘brain’ is on the left and the leg muscles on the ‘right’. The nerve impulse (the moving arrow) travels down the axon ‘driven’ by¬†a change in polarity (charge) across the membrane of the axon. In the resting state, when there is no impulse, this is positively charged on the outside and negatively charged on the inside. Sodium – remember the ‘S’ in the acronym VGSC – is positively charged and¬†crosses the¬†membrane (out to in) via a small pore or hole as the impulse passes. This makes the inside of the axon transiently positive‚Ć. The pore or hole is the VGSC.

Top view of a VGSC

Top view of a VGSC

The VGSC is a transmembrane protein. It actually crosses the membrane multiple times and assembles to form a very narrow channel through which the sodium passes. The cartoon on the right shows the top view of a VGSC, looking “down” the pore into the inside of the axon. The blue bits can move to open or close the pore, allowing sodium to traverse – or not – the membrane into the axon. Apistan binds to the transmembrane protein and prevents the pore¬†from closing. As a consequence, sodium continues to pass from the outside to the inside of the axon, the nerve cannot repolarise and no further impulses can be transmitted. As a consequence,¬†Apistan paralyses the¬†Varroa.

But I don’t suppose many beekeepers will feel much sympathy for the mite ūüėČ

Why isn’t the beekeeper paralysed as well?

Nerve impulses in¬†Varroa and humans are transmitted in essentially the same way. We also have VGSC’s that operate¬†in a similar manner. Why doesn’t Apistan also paralyse careless beekeepers? More generally, why are pyrethroids the most widely used insecticides, available in all garden centres and supermarkets?

Two factors are at work here. The first is the specificity of binding. The VGSC is a protein. Proteins are made from building blocks termed amino acids. The precise sequence, or order, of amino acids is usually critical for protein function. However, two proteins with a similar function can exhibit differences in the amino acid sequence. Although the¬†human and mite VGSC have a similar function¬†they have a¬†different amino acid sequence. Apistan binds much better to the mite VGSC than the human VGSC (this also explains why bees aren’t also paralysed by Apistan … the miticide is specific for the mite VGSC and binds poorly to the honey bee VGSC). In addition, many mammalian species have a number of detoxifying enzymes which deactivate pyrethroids, rendering them ineffective. Together, this explains the specificity of Apistan and other pyrethroids, and the low level of toxicity to humans.

So now you know how Apistan works we can address the much more important question …

Does Apistan work?

Unfortunately, usually not. Since the late-1990’s there have been a large number of publications¬†of Apistan- or fluvalinate-resistant mites from many countries, including the¬†USA (1998, 2002), Israel (2000), UK (2002), Spain (2006), Korea (2009) and Poland (2012). The National Bee Unit used to report¬†Varroa resistance¬†test results by geographic region in England and Wales.¬†Resistance was first reported in mites from Cornwall and Devon (in 2001 and 2002). By 2006 resistance was very widely distributed throughout England. By then approximately a¬†third of all mite samples tested were resistant. The number of tests conducted (or at least reported) then dwindled and there have been none reported since 2010. Not no resistance … no tests. Presumably it’s no longer worth reporting as resistance is so widespread.

The most up-to-date map on the distribution of Apistan resistance I could find is in the NBU booklet on Managing Varroa [PDF; page 28 of the 2015 edition], though the data presented is from 2009.

However, bee equipment suppliers continue to sell Apistan (even Vita, the manufacturer, states that resistance is widespread) and beekeepers continue to use it. Many do so without first testing whether the mite population in their colonies is sensitive to the miticide. How should this be done?

Testing for resistance

Vita suggest two tests. Their first (the “rule of thumb test”) is deeply flawed in my view. It suggests simply looking for a drop of 100’s of mites in the first 24 hours after treatment starts as indicative of a sensitive population.

This isn’t good enough. What if there were thousands of mites present? Perhaps 20% of the population are sensitive, with the remainder resistant‚Ä°. 20% of 5000 mites is 1000 … so you might expect a drop of 100-200 (the majority of the phoretic population) within the first 24 hours. Some might consider this drop indicates a sensitive population … it doesn’t.

It’s not sufficient to¬†count the corpses … you need to know how many mites were unaffected by the treatment.

The second Vita-recommended test is a cut-down version of the “Beltsville” pyrethroid resistance test which is fully described in an¬†NBU pamphlet (PDF). This is much more thorough. Essentially this treats ~300 bees with Apistan, counts the mites that are killed in 24 hours and then¬†counts the unaffected mites remaining on the bees. It’s only by knowing the total number of mites at the start and by determining the percentage of mites sensitive that you can be sure that the treatment is effective.

What is the molecular basis of resistance?

We’re almost there … specific pyrethroids, like Apistan, bind to specific parts of the VGSC. The VGSC is a protein made up of a long connecting chain of amino acids. The binding of the pyrethroid requires an interaction with a small number of¬†specific amino acids in the VGSC. If these particular amino acids change – through mutation for example – then the pyrethroid will no longer bind. If the pyrethroid does not bind the VGSC can open and close again, so the axon repolarises and the mite is not paralysed. The mite is resistant and can then go on to rear lots more resistant baby mites … which, in due course, transfer the viruses that kill your bees.

And that’s exactly what happens.

Leucine

Leucine

A single mutation that causes a substitution of amino acid number 925 in the Varroa¬†VGSC, which is usually a leucine, to either a valine, a methionine or an isoleucine, is sufficient to prevent Apistan and other tau-fluvalinates from binding. At least 98% of mites resistant to¬†Apistan have one of these substitutions. Apistan resistant mites with substitutions at¬†position 925 have been found in the UK, eastern Europe and several sites in South-Eastern USA. It wouldn’t be surprising if the remaining ~2% of resistant mites had a mutation at one of the other amino acids involved in pyrethroid binding. Further studies will confirm¬†this (there are alternative mechanisms that cause¬†resistance, but the one described here is the most frequently seen).

Why aren’t all¬†Varroa mites resistant to tau-fluvalinates?

Apistan resistance has clearly been demonstrated for the last two decades. Resistance is easy to acquire and selection Рin the presence of the pyrethroid Рis effectively absolute. Without the necessary mutation the mites die, with the mutation they survive.

Bees Рand the phoretic mites that are associated with them Рare moved around the place all the time, by migratory beekeepers, by importers and through robbing and drifting between colonies.

Why therefore aren’t all¬†Varroa mites now resistant to Apistan and other tau-fluvalinates?

The answer to that is interesting and suggests strategies that could make Apistan an effective treatment again¬†… but I’ll save that for another time.


‚Ć Only transiently as the charge is reversed shortly afterwards by a¬†similar, though not identical, ¬†mechanism that does not use the VGSC. However, life is simply too short to describe this bit as it’s not needed to understand pyrethroid – or Apistan – activity and resistance.

‡ The incestuous life cycle of the Varroa mite is important here. This post is already too long to fully elaborate on this but the size of the mite population relative to available open brood (and whether you get single or multiple occupancy of cells) will likely influence the proportion of resistant, partially resistant and sensitive mites in a population.

Credits Рthe action potential GIF was created by Laurentaylorj from Wikipedia.

 

CSI: Forensics in Fife

This is a long post. If you can’t be bothered to read it in its entirety the conclusion is …

It’s the viruses wot done it …¬†probably.

But the take home message is that you can learn from colonies lost in midwinter.

Introduction

I always have mixed feelings about midwinter hive losses, or deadouts as they’re called in the US. Of course, I regret losing the colony and wonder whether I could have managed them differently, or prepared them better, to increase their chances of survival. At the same time I’d much prefer a weak colony perishes in midwinter rather than having to mollycoddle them through the spring.

Winter colony losses in the UK vary from year to year but have averaged about 20% over the last decade (BBKA figures and SBA data). Whether these accurately reflect real losses is unclear to me Рthere are no statistics and they are usually by self-selected beekeeper reporting, so possibly unreliable†.

Mollycoddling weak colonies in the Spring … a¬†wasted effort?

The reality is that weak colonies in the spring require a lot of support¬†and still may not survive. Even if they do, there’s little chance they will be strong enough to exploit anything other than the late season nectar flows.

If the¬†colony is¬†weak because of queen problems then they are likely to need re-queening. This requires a spare queen early in the season – not impossible, but it needs planning or is likely to be expensive. In my view you’d be better off using the ‘spare’ queen to make up a nuc from a prolific colony, rather than trying to rescue what might be a basket case.

If the colony is weak because of disease then having them limp on through the spring is a potential disaster for your other colonies. If it doesn’t recover quickly it’s likely¬†that neighbouring colonies will rob it out, both destroying the weak colony and transferring whatever it was ailing¬†from around the apiary.

Finally, the colony might be weak due to poor management e.g. insufficient stores in the early spring when the queen was gearing up to lay again. In this case you might be able to rescue the situation by boosting it with syrup, brood and bees. However, care is needed not to weaken your other colonies. Two half-strength colonies are more work and much less use Рthey will collect  less honey Рthan one full strong colony.

Learning from your losses

So, rather than pampering weak colonies in Spring – particularly if they’re struggling because of disease or queen problems – I’d prefer they expired in the winter. That sounds cruel but isn’t meant to. The reality is that a proportion of all colonies are likely to be lost in the winter … on average ~20%, but significantly more in long hard winters (or perhaps with more accurate surveys!). As beekeepers, all we can do is manage them in ways to minimise these losses – keep strong, healthy colonies and provide them with sufficient stores – and learn from those that are lost.

How do you learn from the losses? By examining the ‘deadout’ and trying to work out what went wrong. You then use this information in subsequent seasons to try and avoid a repeat performance.

For example …

A life in the year of a June swarm

Sometime in early/mid January a colony of mine died.

The colony was alive in early December when treated for mites. It was suspiciously quite at the end of that month when other colonies were flying. It looked moribund by mid-January on a quick visit to the apiary.

I took the hive apart on the 30th of January to see what might have gone wrong.

But before the autopsy, here’s the history of the deceased …

  • 7th June – a small to medium sized swarm arrives in a bait hive. The bait hive had foundationless frames so it¬†was¬†difficult to estimate the amount of bees in terms of ‘frames covered’. My notes state ” … 4-5 frames of bees (ish) …”.
  • 8th June – very brief inspection, two frames nearly drawn. Queen not seen.
  • 9th June – vaporised¬†with an oxalic acid-containing treatment. 21 mites dropped in the first 24 hours. Not monitored after that as I replaced the solid floor of the bait¬†hive with an open mesh floor.
  • 19th June – unmarked queen laying well. My notes state¬†“… suspect this is a 2015 Q on account of the lousy weather we’ve had …”. There was already sealed brood present.
  • 27th June – clipped and marked the queen blue. At this point there were over¬†7 frames of brood in all stages – eggs, larvae and sealed brood – present.
  • Between then and mid-August the colony continued to build up¬†very well … so well I ‘harvested’ three¬†frames of brood and bees to make up nucs for circle splits.
  • In mid/late August I treated three¬†times at five day intervals with a vaporised oxalic acid-containing miticide. My notes in August state¬†” … KEEP AN EYE ON THIS ONE … very high mite levels …” and¬†(after a second round of treatment)¬†in late September,¬†” … mite levels still high …”. Actual mite counts weren’t recorded.
  • In late September/early October the colony was fed with fondant. An additional block of fondant was left on into the late autumn.
  • Further miticide treatment was added in early December. Mite drop was high but not outrageous¬†– about 44/day averaged over the first 5 days, dropping to 3/day over the subsequent five day period.
  • By late December the mite drop was less than one per day … however, by this time I was beginning to be concerned as there was very little activity from the colony on the warm days around Christmas.

The autopsy

I took the roof off the hive and removed the remaining fondant. Some of the fondant had dripped down between the frames but, in taking these apart, it was clear there were sufficient stores present.

The frames were clean. There were no sign of Nosema, which usually appears as distinctive faecal smearing and marking on the top bars, the face of the frames and Рin a heavily infected colony Рthe front of the hive.

The frames were almost devoid of bees. There were a hundred of so clinging to the middle pair of frames. I brushed these away to reveal a dozen or so corpses stuck headfirst down in the cells. This is characteristic of starvation. These particular bees likely died of starvation, but the majority did not (or they would have also been wedged headfirst into the comb).

Having removed the frames the few hundred dead bees lying on the open mesh floor could be seen. Amongst these was the blue marked and clipped queen. The bees on the floor weren’t showing any obvious signs of disease – no characteristic shrivelled wings seen with overt deformed wing virus¬†infection for example.

I’d walked to the apiary so couldn’t take the hive away with me. I therefore sealed up the entrance to prevent any robbing just in case there was¬†disease present that could be transmitted to another colony. In due course I’ll burn old frames, I’ll treat some of the good drawn comb with acetic acid fumes and I’ll clean and sterilise the hive.

Elementary, my dear Watson‡

There’s no really obvious smoking gun, but there are some reasonably¬†strong clues. I’m pretty sure why and how this colony succumbed.

But first, what didn’t kill off the colony? Well,¬†Nosema didn’t and nor did starvation. Sure, a handful of bees in the middle frame died of starvation, but the majority were on the floor and there were ample stores in the hive and some fondant remaining. It had also been warm enough to move about within the colony to get to these stores.

It’s not possible to deduce much about the queen. The colony was strong in late August but not fully inspected after that. My notes state that brood levels were low in late September, but they were in all the colonies I peaked in at that time.¬†She could have failed catastrophically soon afterwards. If she had I might have expected to find signs of attempted replacement¬†e.g.¬†a queen cell, as there were a few warm periods in the autumn. The fact that she was still present is far from conclusive, but suggests to me that she didn’t fail outright. The colony wasn’t full of drones late in the season suggesting she was poorly mated, though there are plenty of other ways the queen can fail. At least until late August she was laying very well.

I think the two main clues are the Varroa levels in autumn and December, coupled with the small number of bees present on the floor of the colony. Taking those in reverse order. There were far fewer bees than I would have expected from a colony that entered the autumn with about 8 frames of brood. This suggests to me that the bees were dying off at a faster rate than expected. Many bees that died off earlier in the winter would have been carried out and discarded on the warmer days.

The Varroa levels were very high in autumn¬†and quite high (at least for my colonies) in December. In the autumn¬†I didn’t¬†record the numbers. A couple of hundred dropped after treatment in December isn’t huge … but I suspect that the colony was much reduced in size by now meaning the percentage infestation was likely significant.

The damage was already done …

Miss Scarlett in the ballroom with the lead piping

I think this colony died due to the viruses transmitted by Varroa, in particular deformed wing virus (DWV). DWV is known to shorten the life of overwintering honey bees Рsee this study by Dainat et al., for full details.

DWV symptoms

DWV symptoms

Why are there no symptomatic bees visible in the carpet of bees littering the floor of the hive? That’s easy … you only get these symptoms in very young bees that have emerged from¬†Varroa-infested brood. In the winter there’s little or no brood (and there certainly wasn’t for some time in this colony). Any bees in this colony that had emerged with DWV symptoms would have been discarded from the colony months earlier. The colony was inspected every 7-10 days¬†from mid-June to late July but there were no obvious signs of DWV symptomatic bees. They might have been missed, but I’m reasonably experienced at spotting them.

My interpretation is that the colony arrived with high¬†Varroa levels and that – despite treatment shortly after¬†arrival – these persisted through to mid-August. The mites transmitted the usual cocktail of pathogenic DWV strains within the colony. High¬†Varroa levels are known to result in the massive amplification of virulent DWV strains in exposed bees. This late summer/early autumn period is a critical time for a colony. It’s when the overwintering bees are being reared. I discuss this at length in¬†When to treat?. These overwintering bees, now infected with virulent strains of DWV, subsequently died off at a higher rate than normal. Despite the colony appearing reasonably strong in late August, many of the bees were carrying a lethal viral payload.

Bees that died in late autumn would have been carried out of the hive and discarded in the usual manner. Overall bee numbers continued to dwindle, leaving just a few hundred and the queen by the year end. We’ve had some hard frosts in the last month. The expired colony is in the same apiary as the bee shed¬†which has a¬†max/min thermometer inside. The lowest temperature seen was -6¬įC during this period. This probably finished them off.

So no crime scene … just another reminder that the viruses will get you if the Varroa levels are allowed to get too high.

Learning from my mistakes

I think I made one big¬†mistake with this colony … way back on the 10th of June, just three days after it moved into the bait hive. I treated for mites, monitored mite drop after 24 hours and then left the colony with an open mesh floor. I should have monitored for longer (mite drop after vaporisation is often greater¬†after the first 24 hours). I would have then realised how badly infested they were and could have taken greater care to reduce mite levels. By mid/late August mite levels were probably¬†catastrophically¬†high. They were hammered down with miticides but the damage was already done. I suspect that this is also a good example of why the timing of treatment is critical.

It’s sobering that an apparently minor oversight in midsummer probably resulted in the loss of the colony in midwinter.

If you got this far, well done. It wasn’t my intention to write so much. Swarms are a significant source of potential disease and carry a disproportionately high mite load … something I’ll discuss¬†in the future.


‚Ƭ†They are not unreliable because they are reported by beekeepers ūüėČ ¬†Not entirely anyway. They are unreliable because they are generally a self-selecting group that report them. The BBKA or SBA ask for beekeepers to complete a survey. Some do, many do not. The BBKA do not report – at least in their press releases – the number of respondents. Self-selecting bias in surveys means they may not be entirely (or at all) accurate. The SBA surveys by Magnus Peterson and Alison Gray are more thorough. For their 2014 report for example the sample size was 350, with a total of 213 respondents (for comparison, there are about 4000 beekeepers in Scotland). With this information, coupled with some additional data – for example, knowing that only 87% of respondents were actually keeping bees during the survey period! – you can determine how representative the survey is.

‚Ä°¬†Sherlock Holmes never uses this phrase in any of the books by Conan Doyle though he does use a number of similar expressions. The phrase¬†“Elementary, my dear Watson” was first used by PG Wodehouse in Psmith, Journalist which was published contemperaneously (1909). The actor Clive Brook used the phrase in the 1929 film¬†The return of Sherlock Holmes.

2016 in retrospect

The end of another year and another season’s beekeeping. Now¬†is a good time to review what went well and what went badly.

The bee shed in autumn ...

The bee shed in autumn …

In terms of my¬†beekeeping year in Scotland, the end of December isn’t even half way through the winter. Although I didn’t open many hives after mid-September (three and a half months ago), unless we get a warm, early Spring I don’t expect to do any inspections until mid-April. That’s another four and a half months to ruminate on the year passed¬†and plan for the season ahead.

The high points

The great escape ...

The great escape …

This was the first full season using the¬†bee shed and I’m already convinced¬†of the advantages it offers. Colonies built up well in the late Spring, appreciably faster than colonies in the same apiary that didn’t benefit from the protection the shed offers. I was able to inspect whatever the weather. Only really warm days were¬†a problem, and that was because it gets uncomfortably hot. The Up-and-Out‚ĄĘ¬†windows (the bees crawl up and fly out) clear the shed very quickly, making it a good environment for grafting larvae when¬†queen rearing without getting buzzed with bees all the time. It would benefit from power, better lighting, a kettle and an armchair … perhaps something to plan for 2017? It’s never going to resemble the palatial setups¬†in some of those German bee houses, but in terms of secure, weatherproof and sheltered accommodation, it’s hard to beat.

Varroa control has worked well this year. A combination of timely applications of treatment and a significant brood break in the middle of the season, meant that colonies went into the winter with low to very low Varroa levels. Some broodless colonies dropped less than 20 mites after midwinter treatment which is very encouraging.

OSR ... can you believe it?!

OSR … can you believe it?!

I’ve also been pleased with the honey flavour this year. By missing the OSR – too cold (the photo above was taken at the end¬†of April) – the early season honey was a heady mix of goodness knows what, and all the better for it. Great flavour and it has sold well. The switch to square jars¬†with distinctive black lids looks good and, coupled with a very simple DIY label, it’s been popular with repeat customers. My honey is currently available – assuming they haven’t sold out over Christmas – from Mellis¬†Cheese¬†in St. Andrews and Edinburgh, and Luvians in Cupar.

The low points

The most significant problems were all related to queens. Firstly, queens from 2015 were poorly mated (as predicted way back in June 2015) and several gave up (stopped laying) or simply disappeared in May/June. Secondly, my own queen rearing coincided with shortfall and an extended period of very poor weather for queen mating. As a consequence, several hives developed laying workers and needed some significant interventions to rescue them.

Drone laying workers ...

Drone laying workers …

All of these problems – some of my own making, but some unavoidable – meant that production colonies weren’t really strong enough to exploit the summer nectar flow. Honey yields from the summer were the worst I’ve had for half a decade, though the flavour was outstanding. I’ve a couple of¬†30lb buckets left that I’m hoping to eke out over the next few weeks in the smallest possible portions. To add insult to injury … it was apparently one of the best years for heather honey and, because of the problems detailed above, I was singularly unprepared to take advantage of it. In all honesty, I’m not wildly disappointed about this as I’m not a great fan of heather honey. However, since I’m in Scotland and heather honey is considered by many as the cr√®me de la cr√®me, I feel I’ve missed a golden opportunity.

The new season

With the winter solstice now passed it’s time to make plans for the coming season.¬†I’ll deal with these¬†in the Spring as this article is already longer than intended.

www.theapiarist.org

It’s been a busy year with posts almost every Friday. This was more than I’d¬†intended at the beginning of the year, but seems to have happened without too much contrivance. Although posted on a Friday, they’re written in the days and weeks preceding (hence explaining the butchered tenses often used).

Keeping it regular

Keeping it regular

I’ve always tried to avoid the diary-like cataloguing of what goes on in the apiary (as there are others who do this much better), instead focusing on a balance between topical items and more expansive posts – often written as separate linked articles (like on¬†Varroa control or queen rearing) – that both reflect my interests and¬†might help others improve their beekeeping … if only by avoiding my mistakes ūüėČ

Page views and visitors

Page views and visitors

Other than a slightly odd dip in July – a belated “June gap”? – visitor numbers and page views showed the expected pattern of increasing interest in mid/late Spring, tailing off again as the season draws to a close. The peak figures in October reflect the interest in feeding fondant and mite treatments. Clearly there’s still some work to do … treating for mites in October is likely to be too late to protect the winter bees from the ravages of deformed wing virus. Over the entire year the original 2014 posting about honey warming cabinets remained the most popular, with articles on feeding fondant, vertical splits, steam wax extractors and foundationless frames getting lots of attention as well.

Search and ye shall find …

Google and most other¬†search engines ‘hide’ the search terms used by viewers to reach a website. This is nominally valuable information, though looking at the terms that do get through the filters makes you wonder … each of the terms below led the viewer to this site (the typos are original) :

circular large 200 frame honey extractor plans … as opposed to a small 200 frame extractor?

wellies with honey bee pucturers on …¬†puctures?

using laser printer in unheated wooden shed …¬†electric heater needed I think

square drones frame homemaking striping images …¬†random word generator?

foundationless sheds …¬†understandable considering foundationless frames and bee sheds

poly queen beekeeping pdf …¬†article on poly queen¬†beekeeping in preparation for 2017

plastic nuc boxes for sale in manitoba …¬†perhaps a little too geographically specialised

simple label design for honey sales in nigeria …¬†see Manitoba

do i feed bees with apiguard¬†…¬†not exactly

is dettol effective against varroa mites¬†…¬†rigorous testing needed and possibly tainted honey?

how to treat a double brood hive with api bioxal¬†…¬†article on beekeeping bankruptcy to follow

houney bees kb shed bnati h or kb kha jays h …¬†yes, that really was a search term

save humanity a topic covered in detail earlier this year

humanity save …¬†there’s a theme emerging here

how do bees save humanity …¬†by pretending to be wasps

Unsocial media

It’s clear that there are whole communities of beekeepers out there with very different online activities – some interchangeably use old-fashioned websites (like this site) and¬†various¬†types of social media, others restrict themselves to Twitter¬†and¬†Facebook.¬†Posts to this site are now also ‘announced’ on Twitter (@The_Apiarist) and Facebook.¬†I still have to get the hang of Facebook as I’ve not previously used it … I¬†don’t even know how to properly link to it ūüôĀ

Anyway … enough for the year. As I write this the¬†winter solstice has now¬†passed, the days will be getting longer and lighter, queens will – particularly now with the warmer winter weather – be starting to lay and mites will be starting to reproduce. There’s very little to do in the apiary, but the new season is definitely on its way …

For 2017 I hope your bees are gentle, your queens are prolific, your supers are heavy and your swarms end up¬†in my bait hives ūüėČ

Happy New Year

Frosty apiary

Frosty apiary

 

Get dribbling

There has been a prolonged spell of cold weather in Eastern Scotland. Temperatures have rarely risen above 5¬įC, with hard frosts overnight. However, a¬†warm front moved in on Tuesday night and¬†the¬†last few days have been¬†significantly warmer‚Ć. The lack of activity at the hive entrances and a quick peek under the insulation through the perspex crownboards¬†(where fitted) indicated the bees were all tightly clustered during the cold spell.¬†Furthermore, the absence of debris¬†on the removable¬†Varroa monitoring trays fitted to many of the open mesh floors, suggested that¬†little or¬†no brood was being reared.

Ridiculous to the sublime

Ridiculous to the sublime

Varroa counts

Varroa trays ...

Varroa trays …

There¬†was another clue that the colonies are likely broodless. I had been recording the natural¬†Varroa drop of a few colonies over the last month. I did this by simply counting¬†Varroa¬†at each¬†visit, calculated on a mites/day basis.¬†Although generally low (and very low in a few colonies), it had been steadily increasing. This is a good indication there were more phoretic mites in the colony … again, presumably due to the absence of suitable brood for them to parasitise.

It’s worth noting that the natural mite drop is a notoriously unreliable method of accurately determining mite levels in a colony. For example, it’s dependent upon the amount of sealed brood in the colony. With no sealed brood all mites must be phoretic. In contrast, with limitless sealed brood 80-90% of the mites are within cells. However, although estimates from¬†mite drop are not¬†hugely accurate, they are¬†a lot better than doing nothing. The National Bee Unit has published a¬†Varroa calculator. This¬†allows you to use a combination of the mite drop per day, the time of year, length of season and level of drone brood to predict the total numbers of mites in the colony. For some inexplicable reason this¬†asks for the level of drone brood in December … with 0% not being an available option¬† ūüôĀ

Time to treat

With little or no brood in the colonies,¬†now is a perfect time to treat with an oxalic acid-containing preparation to hammer down the remaining mite population.¬†I’ve previously discussed¬†the importance of this midwinter treatment (see Two treatments … a double whammy). In many ways it’s preparation for the season ahead, rather than for the protection of the bees already present in the colony. The lower the mite levels are at the beginning of the season, the longer it will take for the¬†mite population to reach dangerously high levels.

BEEHAVE ...

BEEHAVE …

You can model these events using BEEHAVE. This is an interesting in silico model of a beehive. With mite numbers of ~10 at the beginning of the year, maximum levels reached are low to mid-hundreds by late summer, reducing to a couple of hundred the following winter. This assumes no intervening treatment and runs the model using all the default settings. In contrast, using the same parameters but starting the year with ~100 mites, levels peak at between 3000 and 4000 mites, returning to about 1800 in December.

Remember that the National Bee Unit recommends mite levels should¬†not exceed 1000 or there is a risk of “significant adverse effects on the colony”. Therefore, the midwinter treatment is an important preparation for the year ahead, delaying the point at which these dangerously high mite levels are achieved.

Have your hives got less than 100 mites in them now?

Remember also that, with no sealed brood, midwinter is also the ideal time to expose as many mites as possible to the treatment. With the exception of prolonged treatment with hard chemicals like Apistan or Apivar, it’s probably the only time you’ll achieve greater than 95% reduction in mite numbers. With little or no brood present there’s nowhere for the mites¬†to hide.

Dribbling or vaporisation?

An oxalic acid-containing treatment is recommended in midwinter. This can be delivered by dribbling or sublimation (vaporisation). Under optimal conditions, efficacy of the two methods is broadly similar (90%+) though there is some evidence that dribbled oxalic acid is slightly detrimental to colonies (when compared with sublimation, but not when compared to doing nothing).

Sublimox in use

Sublimox in use …

Api-Bioxal is the VMD-approved oxalic acid-containing treatment. If used for dribbling be aware that the suggested concentration on the side of the packet is higher than conventionally used in the UK. It’s also worth noting that it’s not available pre-mixed so has to be made up from powder. In this regard it’s a less useful product¬†than the pre-mixed oxalic acid solution that Thorne’s (and possibly other suppliers) sold each winter. The one- or two-hive beekeeper needs to weigh out very small amounts accurately, or get together with others to make a large batch. Hardly what I’d call progress. Furthermore,¬†the inclusion of glucose and powdered silica (as an anti-caking agent) in Api-Bioxal means it leaves a caramelised mess if used for vaporisation. Although¬†a scouring pad and elbow grease will get rid of this mess, it’s another example of how the “approved” commercial product is actually less good – and no more effective – than the oxalic acid dihydrate that beekeepers have been using for 20 years or more.

Notwithstanding these negative comments, Api-Bioxal works well and is less expensive (per treatment) than most of the other VMD-approved Varroa treatments.

Don’t delay, get out and get dribbling …

The forecast for the next 7-10 days is for significantly warmer temperatures. This means that the queen – if she was having a break from egg-laying – will start laying again. There will be open¬†brood by this weekend and sealed brood in your colonies by¬†about the 15th of December‚Ä°. Dribbled oxalic acid is detrimental to – and may kill –¬†open¬†brood so if this is your preferred method of treatment then don’t delay. If you sublimate you’ve got a few days leeway, but don’t delay any longer than that.

Here are a couple of old videos showing trickling (dribbling) oxalic acid onto a large and small colony in the middle of winter. The Trickle bottle from Thorne’s makes administering the treatment very quick and easy.

Of course, sublimation using an active vaporiser like a Sublimox is even faster and doesn’t involve opening the colony. Here’s an example showing treatment of a recently hived swarm in midsummer … I could have removed the Sublimox after about 30 seconds.

The¬†Daily Mail may be predicting the coldest winter since the last ice age (so perhaps there will be another broodless period¬ß) but I wouldn’t rely on them to influence something as important as the midwinter treatment for reducing¬†Varroa levels.


‚Ć Here’s a perfect example of the problems encountered by the ‘topical blogger’. I wanted to write about midwinter¬†Varroa treatment in the middle of winter, at a time when others – particular new beekeepers – should be treating their own colonies. Typically these treatments are made in late December or early January. However, the long-range (10 day) forecast in late November suggested the second week of December might be suitable. Some of this was therefore written in very late November, the¬†Varroa drop comments added once I’d completed counting around the 4th to¬†the 6th, and the post finished off the following day once I’d treated my own colonies.

‡ This assumes that the queen started laying on the 7th, the first full day with elevated temperatures.

¬ß¬†I didn’t open any colonies to confirm they were broodless. I was happy enough to take the clues from the increased mite drop on the¬†Varroa trays and the absence of debris indicating uncapping of brood cells. However,¬†I was told by friends that¬†other colonies they opened on the 7th¬†were broodless.

 

Helensburgh & District BKA talk

DWV symptoms

DWV symptoms

I’m very pleased to be speaking on the 24th of November (this Thursday) to members of the Helensburgh and District BKA. The talk will be at the rather splendid looking Rhu Parish Church¬†at 7.15pm. The title of the talk is¬†“Bees, viruses and Varroa: the biology and control of deformed wing virus (DWV)”. I’ll discuss aspects of the biology of DWV, particularly relating to its transmission by Varroa, and will then explore potential ways in which bees could be ‘protected’ using either high-tech or low-tech approaches. If you’re attending please introduce yourself when we’re all having¬†a cuppa at the end of the evening … don’t leave it too late though, I’ve got a 2 hour drive home afterwards.

Update

The drive from the east coast to Helensburgh was stunning, with a fantastic pink-tinged sunset lighting up the snow-covered hills around Crainlarich (Stuc a’ Chroin, Ben Vorlich and Ben Ledi). It was bitterly cold and clear.

Stuc a' Chroin and Ben Vorlich ...

Stuc a’ Chroin and Ben Vorlich …

There was a slight delay due to an absentee projector. During this we discussed oxalic acid-containing treatments for¬†Varroa control and the problems caused by the lack of a ready-mixed preparation of Api-Bioxal. Once the projector arrived we were up and running and I covered viruses and Varroa, why we treat when we treat (or perhaps more correctly ‚Äėwhen should we treat for maximum effect?‚Äô) and the influence of drifting and robbing on parasite and pathogen transmission between colonies. That‚Äôs quite a lot to get through in an hour ‚Ķ and I didn‚Äôt. The audience were rewarded for their patience with a well-earned cup of tea and¬†a question and answer session.

The return trip was less visually pleasing other than a great view of a barn owl ghosting along the verges of the A977 near Rumbling Bridge. With thanks to Cameron Macallum and colleagues for their hospitality and a very enjoyable evening.

Those pesky mites

DWV symptoms

DWV symptoms

If¬†you haven’t yet treated your colonies to reduce¬†Varroa levels before the winter arrives it may well be too late‚Ć. High¬†Varroa levels are known to result in the transmission of virulent strains of deformed wing virus (DWV). These replicate to very high levels and reduce the lifespan of bees. If this¬†happens to the ‘winter bees’ raised in late summer/early autumn there’s a significant chance that the colony will die during the winter.

Mite levels in most of my colonies have been very low this year. Partly due to thorough Varroa management in the 2015/16 winter (the only thing I can take credit for), partly due to the relative sparsity of beekeepers in Fife, partly due to the late Spring and consequent slow build-up of colonies and partly due to an extended mid-season brood break when requeening. Most colonies yielded only a small number of mites (<50) during and after a 3 x 5 day treatment regime (to be discussed in detail in a later post) by sublimation.

Infested arrivals

The low mite drop definitely wasn’t due to operator error or vaporiser malfunction. At the same time I treated a swarm that had moved into a¬†bait hive¬†in early¬†June …

Out, damn'd mite ...

Out, damn’d mite …

This is ~20% of the Varroa tray. Have a guess at the number of mites in this view only. Click on the image to read the full legend which includes the mite count.

The image above was taken on the 18th of September, a day or two after starting the¬†second round of 3 x 5 day treatments. The colony really was riddled. When a colony swarms 35% of the mites in the colony leave with the swarm (or, in this case, arrives with it). For this reason the swarm was treated for mites shortly after it arrived in June. It did have a reasonably high mite load but subsequently built up very quickly and didn’t experience the mid-season brood break my other colonies benefitted from.

The colony now has an acceptable¬†mite drop (<1 per day). Similar colonies are still rearing brood – I’ve not checked this one, but they¬†are¬†bringing in some pollen from somewhere – so there’s a possibility the majority of the remaining mites are tucked away in sealed cells. I’ll keep a close eye on this colony through the next few weeks and will be treating again midwinter to further reduce the parasite burden.

Treat ’em right

If you are treating this late in the season make sure you use a miticide that is appropriate for the conditions. Apiguard¬†(a thymol-containing treatment) is almost certainly unsuitable unless you’re living in southern France¬†as it needs a temperature of 15¬įC to be effective. MAQS has a recommended temperature minimum of 10¬įC which¬†may be¬†achievable.

Hard chemicals such as Apivar and Apistan can be used at lower temperatures but there’s little point in treating with Apistan unless you’re certain¬†all your mites are sensitive. They almost certainly are not as Apistan/Bayvarol resistance is very widespread in the UK mite population. Just because you get an increased mite drop in the presence of Apistan does not mean treatment has been effective. Perhaps all you’ve done is killed the sensitive mites in the population, leaving the remainder untroubled. This is what’s known as a bad idea … both for your bees next season and for your neighbours.


‚Ƭ†I’m posting this now due to the large number of searches for, and visits to, pages on use of Apiguard or other¬†Varroa treatments. These are currently running second to ‘fondant‘ in one form or another.

Bee lining for Christmas

Bee hunting

Bee hunting

Following the Wild Bees‚Ƭ†by Tom Seeley is an entertaining little book that would make an ideal Christmas present for a beekeeper. It describes the methods used to locate feral colonies (or any colonies actually) by bee hunting or bee lining, so called because you follow the line or direction they return to the colony from a nectar source you provide. It’s an ideal Christmas book for two main reasons; it’s a summer activity, so will remind the reader that balmy sunny days will – finally – replace the cold, dark days of winter and, secondly, it will allow the enthusiast the time to build the essential two-chambered ‘bee lining box’ which is used to trap, feed and mark the bees being ‘lined’.

I don’t intend to provide a pr√©cis of the method … you should buy and read the book for that. However, as a taster, you can visit the companion website to the book or watch a short video of Tom Seeley bee hunting …

Tom Seeley is a Professor in the Department of Neurobiology and Behaviour at Cornell University. He is a highly respected entomologist and, unlike many scientists, writes in an engaging and accessible manner. He explains complicated experiments in layman’s terms and makes parallels between his observations on honey bees and wider societal issues. Anyone who has read his book “Honeybee Democracy” will appreciate how simple and elegant his description¬†of the science is.

His explanation of bee hunting is no less clear. Following the Wild Bees¬†is really a ‘how to’ guide, rather than a popular science book, though each chapter does contain a separate section on the science behind the ‘how to’, together with lots of anecdotes. The book is subtitled “The craft and science of bee hunting”. If you’re not aware of feral colonies in your own area this book might help you find them … however, if you live in an area with lots of other beekeepers it will probably just help you find their apiaries (and you can also do that with Google maps).

Wild? They’re livid feral.

The most up-to-date review of feral colonies in the UK can probably be found in Catherine Thompson’s 2012 doctoral thesis¬†(brace yourself … this links to PDF of the 173 page¬†thesis!). Catherine surveyed a number of feral colonies in the UK and showed that, although there were limited¬†but significant genetic differences between feral colonies and managed colonies, the feral colonies were no more ‘native’. Catherine also neatly demonstrates the limitations of studying wing veination (morphometry) as an indicator of genetic purity – it usually isn’t. Feral colonies are essentially relatively recent swarms lost by local beekeepers.

Why ‘relatively recent’?

High levels of DWV

High levels of DWV …

The feral bees Catherine studied had much higher levels¬†of deformed wing virus (DWV), both indicative of – and as would be expected of – uncontrolled¬†Varroa infestation.¬†Therefore, whilst it might appear appealing to have colonies of wild bees in the local church tower they’re almost certainly riddled with DWV and¬†Varroa. This presumably explains why so many of the feral colonies Catherine¬†analysed¬†died during the study period (2.5 years). The swarms lost by beekeepers (that occupy the church tower for example) quickly succumb to the detrimental effects of uncontrolled Varroa¬†replication and the consequent transmission of viruses.¬†Furthermore, through the activities of robbing and drifting¬†that feral colony is likely to act as the generous donor of viruses and mites to the¬†local managed beekeepers hives.

Perhaps not so appealing after all.

Conclusions

I recommend you¬†read¬†Following the Wild¬†Bees. Do so sitting in front of a roaring log fire in mid-winter. Plan and build¬†a ‘bee lining box’ (or buy one) and consider where you might go prospecting for ‘wild’ bees once the long summer days return.

But also plan to put out bait hives to catch swarms (yours or others) and clip your queens …¬†every one ‘lost’ is an opportunity to establish a¬†future source of¬†Varroa and virus infestation.

Under offer ...

Under offer …


 

‚Ƭ†ISBN-10¬†0691170266 … it’s worth shopping around for a copy as the prices vary widely (at the time of writing). WH Smiths had it for well under a tenner recently.