Tag Archives: Varroa

Bait hive location

We’re fast approaching the time of the season when colonies will attempt (and manage) to swarm. Swarming is the way bees increase their colony numbers.

Inevitably, because it means the loss of many of the foragers – the honey-gathering workers – beekeepers try and prevent or control swarming. Prevention is better than control, but it can be difficult or impossible to achieve.

Inevitably, a very large number of swarms are therefore lost.

The swarming process has been well-studied by eminent scientists like Martin Lindauer in the early 50’s and Tom Seeley more recently.

Swarming in a nutshell

The colony ‘decides’ to swarm. They rear one or more new queens in queen cells. On the 9th day after the egg is laid the cells are capped. Then or shortly afterwards the colony can be expected to swarm, with the original queen and up to half of the workers leaving with her. Swarming tends to happen on a warm, calm, sunny day (but not always). Casts may follow.

The swarm leaves the hive and settles nearby, in a tree or on a fencepost. Usually this initial ‘staging post’ is a short distance (perhaps 5-20 metres) from the hive. Scout bees fly from this swarm, surveying suitable locations in the area to set up a more permanent residence.

Swarm of bees

Swarm of bees

Actually, the scouts have been hard at work already. Once the swarm issues from the hive they set about persuading all the other scouts that they’ve found the ideal location. This ‘persuasion’ is the topic of the excellent book Honeybee Democracy by Tom Seeley.

Once a consensus is reached (which might take hours or a few days) the swarm leaves its temporary staging post and flies directly to the final location … a hollow tree, the church tower or above your neighbours soffit. There they set up home.

Most swarms do not survive. They get caught in a storm before relocating, they succumb to disease or they eventually starve to death. Since most strong colonies can – unchecked – be expected to swarm every year, the fact we’re not inundated with colonies indicates that most die.

One beekeepers loss can be another beekeepers gain.

Swarms can also be an annoyance to non-beekeepers. ‘Normal’ people. This always surprises me because a swarm is a stunning site and usually totally unthreatening and unaggressive 1.

Nevertheless, they can be an irritation, both when swarming or if they become established in the church tower or a hollow tree. And, without Varroa treatment they will act as a source of disease for other colonies in the locality through robbing and drifting 2.

So, rather than just let swarms disappear over the hedge or horizon, far better to capture them, put them in a hive and manage them properly 3.

There are essentially two ways to achieve this. Get them when they’re at their temporary staging post, drop them into a box and subsequently hive them. I’ve discussed this process before.

Captured swarm in 8 frame poly nuc

Captured swarm in 8 frame poly nuc …

Alternatively, set up one or more bait hives and entice a swarm to choose this location rather than the church tower or a hollow tree. Again, I’ve discussed how to set up a bait hives several times before.

Bait hives in a nutshell

Honeybee Democracy contains the definitive guide to the desirable characteristics of a bait hive. Conveniently it’s a dark box the size of a National brood box (~40 litres) with a small entrance (~12.5cm2) at the bottom. It helps a lot if it also smells of bees. This can easily be achieved by placing an old black brood frame up against one wall. Fill most or all of the rest of the box with foundationless frames 4 and place it in a suitable location.

Bait hive ...

Bait hive …

Which is – finally – what this post is all about.

Location, location, location

Seeley studied the desirable characteristics of both the bait hive and the location in which it is sited. By location I really mean height from the ground and orientation. However, he and others have also investigated how far from the original temporary staging post the swarm are prepared to fly to occupy a ‘des res’.

So, once you’ve prepared your bait hive(s), the three features of the location you need to think about are their a) orientation, b) height above ground, and c) distance from your bees (or other apiaries 5).

The first two are straightforward as Seeley describes in Honeybee Democracy. In the mid-70’s he conducted a series of experiments which showed that bees prefer bait hives that a) faced South and b) are located higher (5m from the ground) rather than lower (~1m) 6.

Most of the studies in Honeybee Democracy use artificially prepared swarms. Seeley would place these on a post and then observe where they relocated to … essentially he was circumventing the natural process of swarming by ‘starting’ them from the staging post. Many were conducted on an island where there were limited options to relocate to … and at limited distances.

These studies weren’t ideal to determine how far a swarm will relocate from its temporary staging post.

This is important in deciding whether to place bait hives in, near or distant from established hives.

Go forth and multiply, or vice versa

It might be logical to expect swarms to choose distant final destinations rather than nearby ones. For example, this might ensure less competition for forage. That would suggest that bait hives should be situated a long way from your own – or other – apiaries.

However, it turns out that when bees multiply they usually choose not to go forth very far. Although there is some contradictory evidence, it appears as though swarms prefer to relocate to nearby sites, rather than distant ones.

  1. Seeley and Morse (1977) demonstrated that swarms chose a nearby (~20m) site rather than a distant site (~400m) 80% of the time 7.
  2. Jaycox and Parise (1981) showed that swarms always chose sites less than 200m from the artificial swarms prepared for their study 8.
  3. Schmidt (1995) demonstrated that artificial swarms chose to relocate from as little as 0.5m to at least 1 km (average ~400m, i.e. much further away than the other studies) 9.

Why they prefer to set up home near to the original colony is unclear. At least one paper speculates it leaves the option to rob a genetically-related (and possibly less defensive) colony more easily.

Pragmatism and practical beekeeping

I set up bait hives every year. I’ve never failed to capture swarms. I’ve also – inadvertently – had swarms occupy stacks of stored brood boxes or supers. The entrances have faced almost every direction, with South East and South probably being the most often occupied.

However, this is a biased survey … I usually use the same site that worked in previous years.

Under offer ...

Under offer …

Although I’ve located bait hives high up on the top of greenhouses or sheds, the majority are on normal hive stands. This is pragmatism, not because they are more attractive to the bees at knee height 10.

I simply don’t want to climb a ladder to retrieve them 😉

Finally, I put them where I can see them and check them. I locate one in the corner of each apiary, as far from my other hives as possible, but probably never more than 10m away.

Pleasure and practical beekeeping

I also always have a bait hive in the garden where I can observe it on a daily basis. It’s great to see the first scouts appear, to watch their numbers increase day upon day, to keep an eye on the weather for a hot calm day … and to try and predict when the swarm will arrive.

Scout bees are not aggressive. They fly in a characteristic manner, checking the bait hive and the immediate vicinity from all directions.

If the numbers of scouts builds up to dozens or hundreds and they all disappear … either they’ve chosen somewhere else or the swam has been captured.

Or they’re guiding the swarm to your bait hive at that very moment.

Wait a few minutes. A swarm arriving is one of the really great sights in beekeeping 🙂


 

2017 in retrospect

The end of the year is a good time to look back at the highs and lows of the season. What worked … what didn’t work … what on earth happened to our weather in June?

Early June 2017 ...

Early June 2017 …

June is an important month here in Fife. Early season colony buildup should be pretty much complete, most colonies will have had some sort of swarm control measures in late May, virgin queens may well be present in many hives, the OSR is over and colonies need to consolidate for the main summer flows.

But instead it just rained.

Rainfall in Fife was 225% the 40 year average, access to apiaries was problematic due to flooding and queens could only get out to mate if they were wearing ‘water wings‘.

Big mistake

Many colonies needed to be, or should have been fed, during June. Mine had reasonable levels of stores as I’d not taken much early season honey. I therefore chose not to feed them. In retrospect I think this was a big mistake.

Although not monitored carefully, I suspect brood rearing slowed, so reducing the colony size to effectively exploit the July/August flows. It was my worst summer honey crop in years.

Lesson one … If this happens next season I’ll continuously feed thin syrup to keep the queen laying strongly.

Doing the splits

Notwithstanding the incessant rain, swarm control – and the inevitable associated queen mating – went pretty well. I generally use splits of one form or another and most queens got out to mate, albeit a little slower than I’d have liked. If swarm control is needed for colonies in the bee shed we can’t do vertical splits (because of the way entrances are organised) and instead just take a nucleus colony away and let them rear a new queen.

Only ‘pretty well’ though because I suspect I lost a cast from a vertical split that went calamitously wrong. I’d left the queenless half far too strong and inadvertently also left multiple developing queen cells.

D’oh!

This wasn’t going to end well  🙁

I did manage to capture and hive another cast from the same colony, but the first virgin queen and well over half the workers were long gone.

So, lesson two (which I’ve been taught many times before 😥 ) is to be decisive when there are multiple queen cells in a split. Either knock them back appropriately (which I’ll explain next year) or split the box up into multiple nucs. Don’t dither. Don’t prevaricate and don’t – as I think I did this year – simply forget to check.

All the gear, some idea

I blatantly poached how to build foundationless frames with bamboo skewers from the internet. I claim zero originality here. It isn’t my idea. However, I’m pleased to say it was a great success. Simple wooden starter strips were also a roaring success. It’s very satisfying when you realise you don’t need to spend £1 per frame on foundation.

Nearly completed ...

Nearly completed …

I’ve used quite a few Abelo poly hives this season. They’re a strident colour – blue and yellow – but reasonably well made. Colonies checked this winter are doing well in them, with bees right up to the side walls on sub-zero days. This suggests to me that they are well insulated.

An Abelo/Swienty hybrid hive ...

An Abelo/Swienty hybrid hive …

There are some aspects of these hives I have yet to be fully convinced by; upper entrances, the crownboard, high condensation levels and a small Varroa tray. I’ll review them more fully when I’ve been using them for at least a full year.

Old invasives …

The bête noire of most beekeepers, the Varroa mite, has featured heavily throughout the year. In print, though thankfully not in my colonies. I’ve tried to emphasise the need to treat appropriately, using the right miticide at the right time. Since most approved (and even some unapproved 😉 ) miticides are all pretty effective, the timing of treatment is probably the most important point.

2016 temperature data and OA treatment ...

2016 temperature data and OA treatment …

In three recent posts I presented the importance of midwinter treatment, how to prepare the oxalic acid-containing miticide and how to administer it. These should probably be read in conjunction with an earlier article on when to treat, which I’ll come back to in a minute. Finally, as far as Varroa is concerned, I discussed potential ways to optimise the timing of the winter treatment by watching the weather. I suspect that most beekeepers treat too late in the winter.

If you have yet to treat this winter … get a move on!

… and new ones

The new invasive that got some coverage was, inevitably, the Asian hornet. Having first arrived in 2016 I think we’ll be subjected to annual incursions until it gets established here. Constant vigilance is going to be needed to help postpone what might be inevitable. Just because it is inevitable doesn’t mean we shouldn’t try and delay it’s permanent arrival.

Devon beekeepers got some first-hand experience of how vigilant you need to be to both spot and photograph Asian hornets in September. Martin Hocking has written about his experience in the Devon Beekeeper (pp172 and also in November’s Bee Craft)  which should be required reading for beekeepers, with a follow up article about his experience in December (see pp196). There’s an open meeting on the 20th of January at Harberton Parish Hall, TQ9 7SD where the threat posed by the Asian hornet – and how to mitigate it – will be discussed.

Although rarely mentioned this year, Small Hive Beetle now appears to be established in the Calabria region of Southern Italy. Data updated in late September and November indicates that positive wild colonies and sentinel nucleus colonies are still being found, indicating that attempts to eradicate the beetle have failed. Infested colony numbers are perhaps a bit lower than previous years, but since there’s no readily-available data on the level of surveillance, it’s not clear whether this shows that control is having an effect, or if people are just not looking as hard.

www.theapiarist.org

Posts have been made every Friday of the year, with a few additional ones when something important happened (Asian hornets or I was ‘advertising’ a Convention I was speaking at … OK, my talk wasn’t important, but the Welsh Beekeepers Convention was 😉 ).

Regular as clockwork ...

Regular as clockwork …

The Friday posts are intentional. It’s when most of us have time to read stuff. The regularity was not and, frankly, it’s a bit of a surprise I’ve achieved it. However, there it is. No promises it’ll continue like that. You can register to receive email notification of new posts in the right hand panel.

Visitor numbers to the site are markedly increased from last year. Page views per visit are down fractionally, but not significantly. It’s clear that more are finding the site as it becomes better indexed by the search engines, and as pages are referenced by other sites.

24 months on www.theapiarist.org ...

24 months on www.theapiarist.org …

My attempts at generating a presence on Facebook was an abject failure. I simply don’t have time to do anything other than automagically post updates from here on Facebook (as I do on Twitter, which I’m a bit more familiar and competent with … follow me on @The_Apiarist). Apologies if you tried to ‘Friend’ me (or whatever) on Facebook. I’ve cancelled all the email updates as I simply couldn’t keep up. Or, when I tried, I didn’t know how to! I belong to the pre-FB generation, or the one before that.

Beekeeping is international, with different problems – but many shared ones – globally. I’m grateful to the visitors from 161 different countries and the European Union 🙂 Less than 50% of the readers are from the UK, despite the UK-centric bias I inevitably exhibit (°C, colour, no mention of queen castles or slatted racks, precious little discussion of Langstroth hives etc.). Southern hemisphere beekeepers don’t even do things at the same time of the year, so many of the posts aren’t even topical for readers in Australia, New Zealand and South America. Whatever, I’m grateful people took the time to visit and read stuff.

And the winner is …

I don’t publish visitor numbers, but I do comment on the popularity of particular pages. For several years a post on my honey warming cabinet has been the most popular. It was originally posted ‘way back’ in 2014. Frankly, it was useful, but not particularly challenging or exciting.

But it’s all change this year. Aside from the homepage, the archive and blog pages, all of which people arrive at to to get the most recent posts, the honey warming cabinet post was a distant fourth in the 2017 rankings.

Above it were posts on vertical splits and making increase, feeding fondant and – particularly pleasingly and top this year – when to treat colonies with miticides against Varroa. I say particularly pleasingly as the When to treat? post is a serious article on an important subject, underpinned by scientific arguments. The timing of the late summer treatment is probably one of the most important events in influencing the health and overwintering success of the colony. This post was almost twice as popular as any other post this year which – because it originally appeared in early 2016 – suggests it is finally being widely cited and accessed by beekeepers.

When to treat?

When to treat? Finally getting read when it should be.

And what does the future offer?

Frankly, as I write this in mid-December with a streaming cold, a box of tissues and slathered in Vicks VapoRub (really, it’s not a pretty sight) I don’t know. I have two priorities at the moment; getting the new bee shed properly setup and (with my researcher hat and lab coat on)  starting studies of Chronic Bee Paralysis Virus. Both will get coverage here.

Bee Shed 2 ... the windows still need some work.

Bee Shed 2 … the windows still need some work …

In terms of the website I’m acutely aware there’s no proper indexing or rational list of articles on particular subjects, perhaps other than Varroa. I hope to bring some order to the chaos, allowing me to not repeat myself, to develop some themes more fully and to not repeat myself 😉 . I also know I have a load of unwritten stuff on queen rearing.

Winter time is also DIY time … dabbling with wood, perspex, Correx and Elastoplasts. Something will surely result from this, in addition to the blood loss and bad language.

If there are things you’d particularly like to read drop me a note. I’m interested in the science underlying beekeeping and have little patience with some of the dogma and That’s the way we’ve always done it stories. I’ve already written about the importance of training and the responsibilities of beekeepers. I’ve got some more on these areas planned as I think they’re too often ignored by beekeepers in the UK.

With Best Wishes for 2018. May your colonies be docile, your supers unliftable, your queens well-mated and your swarms (again) in my bait hives 😉

Happy New Year


 

 

If Carlsberg did vaporisers …

… they’d make the Sublimox sublimator.

I wonder how many beekeepers have one of these on their wish list for Santa?

Sublimox vaporiser

Sublimox vaporiser …

From being a bit of an imported oddity (I had to import mine from Icko Apiculture in France three years ago) they’re now becoming mainstream … over the last year or so they’ve been sold by an independent importer, then Abelo and – just this month – the ‘Big Daddy’ of UK beekeeping suppliers, E. M. Thorne (Rebecca at Thorne’s kindly asked if they could include links in their December newsletter to previous posts here on the Sublimox and vaporising Api-Bioxal).

The Sublimox is also now being discussed more widely on the online forums, with much of this discussion emphasising the price (they are expensive). Aside from this disadvantage, I think there are a number of significant advantages of this design of sublimator (vaporiser) which are worth emphasising.

The general principle of active and passive sublimators

Sublimators (vaporisers) are designed to heat oxalic acid (OA) crystals sufficiently that they sublimate i.e. go through a phase transition from a solid into a gas without an intervening liquid phase. As readers of this site should know, oxalic acid is highly effective against the Varroa mite – both by sublimation and trickling in solution, which has recently been covered in excruciating detail so won’t be elaborated on here.

Varrox

Varrox

Many sublimators (vaporisers) are passive. You add the OA to a pan, slide it into the hive entrance, apply a current to heat the pan, allow the OA to sublimate, withdraw the pan and start again. You usually need to cool the pan in water before addition of the next dose. This heat, rinse and repeat cycle takes time, but is very effective and the pan-type vaporisers are relatively inexpensive (£35-£100).

The Varrox vaporiser is one of the original and best known models, though there are any number of much less expensive copies sold by beekeeping suppliers and on eBay. Most require a 12V supply of some kind.

In contrast to these, the Sublimox is ‘active’, as is the US equivalent machine, the ProVap 110. In these the pan is pre-heated, the OA is ‘dropped’ into the pan in such a way that the vapour is generated in an enclosed space which it then escapes under pressure through a nozzle.

Probably the best sublimator in the world …

In terms of speed, convenience and ease of use I’d argue that the Sublimox is hard to beat.

Quick

Delivery of a single dose takes no more than 45 seconds from inserting the Sublimox nozzle into the hive. It’s appreciably faster than the pan-type passive sublimators. There’s a preliminary warming up period before use, as the machine reaches operating temperature. After that it’s simply treat, refill, treat, refill ad infinitum. The rate-limiting step is sealing the hive and refilling the small plastic ‘cartridge’ with OA.

For one person, a hive-a-minute is just about possible – if you have 10-20 closely spaced hives, sufficient entrance blocks and buy additional white plastic cartridges. But, to achieve this you’ll be rushing about like a mad thing and it’s not realistically achievable1.

But speed isn’t the major benefit.

Convenient

Sublimox vaporiser

Sublimox vaporiser

It’s convenient because you can ‘squirt’ the gas through a small hole in hive. You don’t need to open the hive and so it works with any hive type or entrance. My favoured kewl floors cannot be used with a sublimator that needs to be pushed through the entrance. Instead, all my hives have a neat 6mm hole drilled through the sidewall of the floor which is usually plugged with a small foam bung or twist of grass2. Vapour quickly permeates throughout the hive, ensuring all surfaces are reached.

The only exception are the all-poly hives, such as the garishly coloured Abelo’s I’ve been using for work this season. The nozzle of the Sublimox gets hot and melts polystyrene (been there, done that 🙁 ). With poly hives I usually use a simple shallow eke with a Sublimox nozzle-sized hole in one side. In this case you do need to remove the roof and crownboard, add the eke, replace the roof (upside down), treat and then close up the hive.

Foam bung ...

Foam bung …

The alternative is to simply squirt the gas through the open entrance. This isn’t ideal as some of the gas will escape, potentially exposing the beekeeper and definitely not exposing the bees/mites. One way to avoid this loss of gas is to use a wooden block with a small hole through the middle held over the poly hive entrance.

It’s important to have a clear space into which the gas is ‘squirted’. If you don’t the OA tends to not permeate through the hive properly.

The Abelo hives have a hole in one face of the brood box. This is usually plugged. I think it’s intended as an upper entrance. I’ve yet to try poking the Sublimox nozzle through this hole to deliver the OA … this might not work as it may be too close to the frame, so impeding the spread of gas through the box. Time will tell.

Safety considerations

There’s an additional benefit of the way the Sublimox is used. Operator exposure to OA should be minimised. The gas isn’t generated until the machine is inserted and inverted and takes no more than ~45s to deliver. If the hive is sealed properly there’s very little exposure to the gas.

… but all this comes at a cost

The Sublimox is three-times the price of a Varrox vaporiserIs it worth it? That’s up to the purchaser to decide, based on the number of hives to be treated, the depth of their pockets, the perceived benefits of the speed, ease of use, convenience and safety etc.

Many will baulk at the cost. Some build their own. Others don’t bother vaporising, but solely dribble OA solution in midwinter. This is the cheapest and fastest way to treat colonies. I estimate it costs about 0.5p/hive to trickle treat if you buy OA in 25kg bags. Dribbling is probably even faster than using the Sublimox. However, dribbling is really only practical for broodless colonies – swarms and for midwinter use – and should only be done once per season. In contrast, repeated sublimation is tolerated well by colonies.

Would I buy another one?

Almost certainly.

Before you splash the cash

Generator

Generator …

Be aware … the Sublimox requires a 240V supply. One of my apiaries has mains power which is the best solution, but unlikely in the corner of a farmers field. You can use an inverter from a car battery which is fine if you can get your car close enough to the hives. Alternatively – and this is what I do – you can use a portable generator. I’ve got an 700W Impax one from Screwfix which works perfectly.

But that’s another £190  🙁

You’ll also need to periodically buy replacement sealing rings for the OA “cassette”. These wear out or perish rather fast. Icko sell them for a daft price, but they’re now available in the UK.

Single use ...

Single use …

You should also be aware that Api-Bioxal, the VMD-approved oxalic acid-containing miticide, has glucose in it which caramelises in the pan of the Sublimox (and other vaporisers) and is a bit of a nightmare to clean out properly. I’d go further and suggest that Api-Bioxal is unsuitable to use with a Sublimox. If the nozzle is blocked the gas has to escape and there could be inadvertent exposure of the operator.

Safety first

I’ve touched on safety above. However, just because OA vapour is generated for a very short and well defined time doesn’t make it safe. There are still exposure risks which must be taken seriously.

You’ll need PPE – personal protection equipment – to prevent exposure to the OA vapour when treating colonies. This includes eye protection and a suitable vapour mask. Don’t skimp on this and assume you’ll just stand downwind. If the hive is poorly sealed, swirling gusts of wind will expose you to vapour and it’s – at best – very, very unpleasant.

Entrance block

Entrance block …

Unlike passive vaporisers, the Sublimox generates a very large volume of gas immediately the OA is added. There’s no opportunity to ‘stand well back’ as the pan warms up as you can with the passive machines. You have to be holding the Sublimox to invert it and drop the OA into the pan. You’ll be bent over the hive and unable to avoid the swirling fog of acidic vapour if it escapes. To help minimise this seal the hive thoroughly. I use a full-width entrance block and tightly fitting Varroa tray. Even then, particularly on ageing cedar hives, there are all sorts of little gaps from which the OA vapour can be seen escaping.

Entrance block in use

Entrance block in use …

Finally, as if gassing yourself with an evil smelling acidic cloud of OA wasn’t enough, remember you’re using a 240V supply outside, probably on damp grass … or possibly even in the rain. Don’t get electrocuted. Make sure you use an RCD (residual current device) that’s been tested and you know works.

Take care.

Share the costs

At the time of writing the Sublimox costs over £300. Perhaps competition will force the price down a bit? When you consider that these machines are used relatively infrequently during the season it makes sense to consider purchasing them as an Association item (or with a group of friends), in the same way that some associations have extraction equipment available.

When compared to a reasonable extractor the Sublimox doesn’t seem so outrageously priced.

Of course, like an extractor, everyone needs it at about the same time of the season (at least in midwinter). However, unlike an extractor, it’s generally needed for a relatively short period, is easy to transport and easy clean after use. There should be no reason it couldn’t be shared by association members.

I appreciate that many associations don’t have shared equipment, or many beekeepers don’t belong to their local association. All I’m doing is suggesting a way in which a good quality and highly effective piece of equipment could be purchased so that many can benefit.

Whether you’ve got one of these on your list for Santa or not …

… Happy Christmas!


1 The rate-limiting step is probably having enough entrance blocks. If removed too soon you’ll lose lots of vaporised OA goodness. Leave it a good 5 minutes if at all possible, which is easily enough time to treat another 5 hives. See what I mean?

When treating a hive for the first time I’ve even drilled this hole through an occupied hive.

† Actually, this hole isn’t suitable. It opens onto the face (rather than end) of a frame, and the vapour is therefore restricting from spreading. Don’t bother.

‡ I’ve regularly treated colonies in the dark. Sometimes the only time I can get to the apiary is after work. The bees are all ‘at home’ but you can easily seal the hive up and treat them. Use a headtorch with a red bulb. Since bees can’t see red, any that escape won’t directly target your head and you can probably work safely without a veil.

Colophon

If Carlsberg did … is one of the most recognisable advertising campaigns of all time. Originally created in 1973 it has achieved near-universal recognition and remains in daily use, though predominantly these days as internet memes. The opening three words of the adverts were as recognisable as the closing seven … probably the best lager in the world.

There are any number of comedic If Carlsberg did ‘advertising’ campaigns, including some from Carlsberg itself … Probably the best poster in the world, featured the distinctive swirly underscore, colour scheme and font, together with a real tap dispensing lager installed in Londons Brick Lane.

If Carlsberg did ...

If Carlsberg did …

Carlsberg revamped the advertising campaign in 2015 (the poster above was part of this), over 40 years after it was first used. You can view these adverts on the Carlsberg website.

I’ve used a variant of the If Carlsberg did … phrase previously, when describing the large Dadant smoker. It’s still a great smoker.

Bee shed 2: the sequel

All good things must come to an end, though this particular one did sooner than I’d hoped.

Our research apiary – affectionately known as The Bee Shed – lies in the path of a recently announced new road development. Not close to, not within sight of, but actually underneath a proposed access road to the new Madras College site to the West of St. Andrews.

Under construction ...

Under construction (mid/late 2015) …

The timing stinks

There are actually two preferred access road routes to the new school, but the Council (who in their infinite wisdom drag everything out to the last possible minute before committing) won’t decide which will be used until about a month or so before development is expected to start. This is intended to be early in 2018 i.e. rather too close for comfort if we don’t want our research interrupted.

We’ve known about the possibility of the new road since June, but things never seem to move as fast if there’s not a deadline looming.

We therefore need to prepare a second research apiary, move all the bees across and then disassemble the original one … all within the next few weeks.

Time spent in reconnaissance …

… is seldom wasted. And we’ve spent quite a lot of time. We’ve considered a number of alternative sites, some better than others, but none truly ideal.

Given the choice we’d have selected a sheltered, East/South facing site, surrounded by mature open woodland, with water close by, protected from strong winds by the adjacent woodland or walling, with abundant local wildlife, early pollen and …

No, stop, wait!

The bee shed in autumn ...

The bee shed in autumn (2016) …

That’s a description of the current site.

In fairness, there were some issues with the original apiary location. It was low lying and prone to minor flooding. Access was across a rickety set of scaffolding planks that threatened to pitch us into the burn when wet and slippery. Crossing the burn with the hivebarrow – particularly in the dark – required some courage (or stupidity). There was no power in the shed, it was quite remote and it was a bit on the small side.

There were some wonderful orchids though …

Common spotted orchid

Common spotted orchid …

I suspect these will struggle to re-emerge through the tarmac of the new road 🙁

Bigger and better

We’ve had to compromise on the new location, but – in doing so – we’ve managed to correct some of the shortfalls of the original site.

We’ll now have much more space and better drainage. We’ve achieved the former simply by specifying a larger footprint, and the latter by building on an earth mound raised a few feet above the water table. We’ve invested in solar powered lighting systems and have excellent shelter from the cold Easterlies that sweep in off the North Sea.

It’s also better located for outreach activities and closer to the research labs.

The final plans include a 15m x 15m platform to house a new bee shed of 16′ x 8′. Once we’ve vacated the original shed (a tiddly 12′ x 8′) it will also be moved to the new apiary, giving us additional storage and colony space.

In total we should have capacity for about a dozen colonies under cover, with more outside if needed. I should have added earlier … the two primary goals of housing bees within a shed is to  provide greater protection, enabling both a slightly longer brood rearing season and allowing inspections and brood harvesting whatever the weather.

If we absolutely have to inspect/sample on a Monday morning during a downpour, we can. The beekeeper saunters over under an umbrella, dons his/her bee suit and does the work. The bees don’t react badly to inspections in inclement weather. They simply exit the shed via the windows and re-enter the hive by a short tunnel through the shed wall.

Landing boards ...

Landing boards …

Over the next few weeks I’ll document some of the developments as we start to prepare for the 2018 season.

Here’s what I prepared earlier

Here are a couple of photos of the apiary in the very early stages of preparation.

Dig and Dug build an apiary

Dig and Dug build an apiary

The compacted grit base and shed foundations are now complete, with the shed and the fencing due shortly … and then it’s my turn to have a dabble preparing the shed for the bees, installing the windows and entrances and the solar power lighting system.

Early/mid December foundations and base installed

Early/mid December foundations and base installed

More of the same.

Shed foundations

Shed foundations

And then there’s the small task of moving the bees in …


This quote (Time spent in reconnaissance is seldom wasted) is sometimes attributed to the talented and successful German Field Marshal of World War Two, Erwin Rommel. However, there are numerous other proposed sources … Sir MacPherson (Mac) Robertson (1860 – 1945), Field Marshal Arthur Wellesley The 1st Duke of Wellington (1769 – 1852) or Sun Tzu (544 BC – 496 BC) in The Art of War. Take your pick. The meaning is self-evident … when planning something it’s worth considering all the possibilities, in particular the environment.

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Weather to treat

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

Midwinter OA-based treatments

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

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

The beekeepers winter dilemma

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

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

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

Memories of midseason

Memories of midseason

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

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

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

An alternative approach is needed.

The annual brood rearing cycle

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

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

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

Of these, temperature probably has the greatest influence.

Probablyß.

Generalised annual brood and worker numbers ...

Generalised annual brood and worker numbers …

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

Temperate(ure)

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

And then there’s the year to year variation.

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

Watch the weather

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

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

Ho ho ho

Ho ho ho

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

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

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

The proof of the pudding

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

2016 temperature data and OA treatment ...

2016 temperature data and OA treatment …

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

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

And again …

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

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

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

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

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

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

A Hi tech solution?

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

Brood rearing starts ...

Brood rearing starts …

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

Stop press

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

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

It was broodless, as I’d hoped  🙂

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


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

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

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

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

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

Colophon

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

Anonymous

 

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Principles and practice

There’s a high level of ‘churn’ amongst new beekeepers. Beekeeping is relatively easy and inexpensive to start. The principles of beekeeping appear straightforward. But large numbers of beginners give up after a season or two.

Here I argue that the colonies and hives some of these beginners abandon pose a threat to other beekeepers, sometimes for years …

A better appreciation of the commitment required to successfully practice the principles of beekeeping might increase the success rates of beginners, though it might also dissuade some from starting in the first place.

Save the bees, save humanity

Supermarket bees

Supermarket bees …

Bees are popular. You only need to visit the supermarket, spend time on the High Street or browse the web, to find bees or pollinators mentioned. The plight of the honey bee is extensively documented in the press. In places some of these references are little more than thinly-veiled adverts … there are any number of beers or ales that now include ‘local honey’ to support bees and beekeeping.

So, public awareness is high.

A good thing

In some ways this is a good thing. The public are aware that, for a variety of reasons, our honey bees (and other pollinators, but I’m going to restrict myself to honey bees for the remainder of this post) are facing real problems. Habitat destruction, monoculture, disease, farming practices, global warming, mobile phone masts, parasites, imports and – the current favourite – neonicotinoids, are all/solely (delete as appropriate) to blame for the problems faced by our cute little bees.

Monoculture ... beelicious ...

Monoculture … beelicious …

It’s a good thing because you might get to sell more local honey which, as a consequence, means you’ll look after your bees carefully and manage them to make more honey next year. It’s a good thing – and I’ll declare a vested interest here – because the Government is encouraged to spend money on research to discover what the real threats to honey bees are (hint, it’s probably not mobile phone masts). This money will also help develop ways to mitigate these threats in due course.

There are a lots of other reasons why it’s a good thing. People are designing bee-friendly gardens, they’re planting wild-flower meadows, they’re reducing pesticide usage and favouring biological control or other pest management techniques. Farmers are being encouraged to leave wide field margins or build beetle banks … and some might even be doing this.

Too much of a good thing?

Some people are so concerned about the plight of the honey bee they decide to do the obvious thing and buy a hive and bees for the bottom of their garden. Obvious, because they’ve increased the number of hives and they’ll be getting lots of delicious honey at the end of the summer.

Some attend a winter ‘start beekeeping’ course (or fully intend to next year, once they’ve kept bees for the current season). Some think they’ll be OK with generous offer of telephone support from the person who sold them a midsummer nuc.

Others do this without any training, without any advice and without anyone to mentor them. 

What could possibly go wrong?

These new beekeepers are certainly well-intentioned. They fully intend to help bees. They really think they’re going to help. They love the idea of their own local honey.

Unfortunately, although many might think they appreciate the basic principles of keeping bees, they know very little about the practice of beekeeping.

Principles

Actually, the principles of beekeeping are a little more complicated than buying a hive, dumping a nuc into it and harvesting the honey at the end of the season.

The bees need to be fed when there’s a dearth of nectar, or in preparation for winter. They need to be protected from pests and diseases. They need space to expand. They need to be monitored in case they’re thinking of swarming. If they are, action is needed. And all this needs to be regularly and repeatedly checked throughout the Spring and Summer.

In short, they need to be properly managed. This management is the practice of successful beekeeping.

Without proper management I’d argue that one of the biggest threats to bees and beekeeping is the unmanaged colony (or hive) lurking in the corner of a field.

Practice

It’s easy to overgeneralise here. The following paragraphs are really describing beekeepers in their first few seasons. Experienced beekeepers can modify their management practices to one that suits their bees, environment, climate and strategy. Bear with me.

Inspections need to start before colonies build up too strongly in the Spring. Queens should ideally be found and marked (and clipped in my view, but some prefer not to do this). Inspections continue at 7 day intervals until the swarming season is well and truly over.

Not 11 day intervals … not when “the weather is better than today”, not when “I get back from the  fortnight in Crete”, not when “I can be bothered” … and certainly not only when “the neighbour is angry about the swarm clustered on their garden swing”.

Inspections have to be conducted thoroughly and with a purpose. It’s not a cursory glance in the top of the box. There’s a reason you’re doing it, so do it well.

Inspections must be done even if it’s 32°C in the shade and you’re melting in your beesuit, when the bees are stroppy as the OSR has just gone over and there’s no nectar coming in, when the weather is (again) miserable and all 50,000 will be ‘at home’ (and possibly tetchy as well) and even if you think “surely they’ll be OK for another day or two?”.

They probably won’t.

Hard labour

Beekeeping is hard work. If you’re lucky and the supers are bulging full it can be backbreaking.

You have to work reasonably fast and carefully. Manage only one of these two and, for different reasons, inspections can become tiresome.

You will get stung, though not often if you’re fast and careful and if you have well-tempered bees.

It can be hot as hell in summer and you can get wet, miserable and cold at any time of the season.

Uh oh ... swarming ...

Uh oh … swarming …

It’s not only physically hard, it is also mentally hard. Not like quantum physics, but it still requires quite a bit of thought. Bees are not ‘fit and forget’.

Using a combination of observation, experience and knowledge (and perhaps a little inspired guesswork) you need to determine what’s going on in a forty litre box containing over 50,000 bees. Is there disease present? Is it one you can do anything about? Is it notifiable? Is the queen present and laying well? Is the colony thinking of swarming (hint, a dozen sealed cells is usually an indication the colony has swarmed, not that it’s thinking of swarming 😉 ). Do they have enough stores? Do they need more space?

You need to be prepared for disappointment (and have a contingency plan). Despite your best efforts the colony may swarm. An extended period of lousy summer weather prevents the new queen from getting mated properly. The colony dwindles, is too weak to defend itself and is robbed out by another colony. Any number of things can go wrong.

Bees are managed, not domesticated.

That’s the reality of beekeeping. That’s the practice that underlies the principle of just dumping a nuc of bees in a box in late April and harvesting pound after pound of golden honey in early September.

If only it were that simple!

Beeless “beekeepers”

I regularly meet people who ‘once kept bees’. I’m sure you do to. Further discussion often shows that they certainly once had bees, but that they failed to keep them.

The colony died, was robbed out, repeatedly swarmed, absconded or – much more frequently – these beekeephaders simply lost interest.

Often they aren’t actually sure what happened to the colony. Have you ever asked them?

Their initial enthusiasm was tempered a bit by the first couple of inspections. The colony was getting much bigger, much faster than their experience made them comfortable with. They got a bit frightened but wouldn’t actually admit that. They missed an inspection (or two) as they were in Crete for the family holiday. The colony swarmed. They’d read somewhere that the colony shouldn’t be disturbed for a month, so they didn’t. They remembered again three months later but were then too late for the autumn Varroa treatment. Have you got any fondant to spare? They’ll have another go next year.

Definitely.

It’s not unusual for these hives to be simply abandoned. You find them in the corners of fields or tucked up against the hedge in a large sprawling garden.

Out of sight and out of mind.

Forgotten, but not gone

Forgotten, but not gone …

The gift that keeps on giving

Sometimes the colony limps on for a season or two. More often though it expires in the winter. The hive may then be repopulated the following year by a swarm. They flourish, or more likely perish and are repopulated again. Even if mice move in for winter and wax moth trashes the comb they still attract swarms.

duunnn dunnn ...

duunnn dunnn …

There’s a dozen or more hives like this on private land I know of. Some local beekeepers visit every year or so to collect any swarms that have moved in. I can’t imagine the state of the comb … or the colonies they collect.

But (queue Jaws music … duunnn dunnn… duuuunnnn duun… duuunnnnnnnn dun dun dun dun dun dun dun dun dun dun dunnnnnnnnnnn dunnnn) these abandoned and unmanaged hives mainly provide a great opportunity for Varroa to flourish. Together with both the foul broods, Nosema and goodness knows what else.

The abandoned hives effectively act as bait hives, attracting swarms which become established feral colonies. Most will eventually be decimated by Varroa and its viral payload, but many will chuck out a swarm or two first, or drones that drift from colony to colony. Some will get robbed out as they collapse – perhaps by one of your strong colonies – leading to a huge infestation with phoretic mites carried by the returning robbers.

They’re like a 40 litre cedar version of Typhoid Mary.


† And my extensive market research suggests they are very delicious too 😉

‡ After all, there’s no time like the present to start and the sooner you buy and populate that lovely cedar hive, the faster honey bee colonies numbers will increase. But they will definitely attend the beekeeping course next winter. Absolutely!

Telephone support. Really?! Have you ever tried to give telephone advice to a new beekeeper who’s standing by an open hive, mobile clamped to their ear, desperately looking for eggs, or deciding whether the queen cells are capped or uncapped? I’ve tried … don’t bother. Grab the beesuit and get to the apiary 😉

There are others I know of and have access to. The entrances to these have miraculously become stuffed tight with grass, so preventing their repopulation. How did that happen? 😉

A poor analogy, but it makes the point. Typhoid Mary (Mary Mallon) was an Irish immigrant  New York cook in the early part of the 20th Century. She was also an asymptomatic carrier of typhoid, a bacterial infection. During the period 1900-07 she infected at least 51 people, three of whom died. Investigative epidemiology traced a series of typhoid fever outbreaks to places where Mary Mallon worked. She was named Typhoid Mary in a 1908 article in the Journal of the American Medical Association.

Mary Mallon

Mary Mallon

Mary Mallon refused to accept that she was infected, was forcibly incarcerated (quarantined) twice and eventually died after three decades of isolation. The analogy is poor because Mary Mallon appeared in good health, whereas these abandoned hives (and the bees they contain) are often pretty skanky. However, the term “like Typhoid Mary” is often used to indicate a source of repeated infection … which is spot on.

 

 

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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  🙁  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 😉

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’ 😉

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 😉

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 😉  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 Warré 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  😀


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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Trick(le) and treat

Tools of the trade

Tools of the trade

This is the third and final post on why, with what, when and how to minimise mite levels in colonies in midwinter.

In the first post I explained why midwinter mite treatment makes sense. In the second I described how oxalic acid-containing solutions should be prepared and stored.

Oxalic acid-containing” solutions includes both Api-Bioxal, the VMD approved treatment, and the unadulterated chemical. All three posts focus on trickling or dribbling – I’ve covered sublimation previously and both are essentially equally effective. Sublimation or vaporisation is currently very fashionable … but trickling is simplicity-itself and requires almost no special equipment.

In this post I’ll discuss how to administer the oxalic acid-containing solution.

For readability I’ll use the term OA solution to mean any oxalic acid-containing solution. About 50% of the readers of this site are from outside the UK; local rules may determine what you are or are not allowed to administer to your bees.

Trickling or dribbling

You’ll hear both terms used interchangeably1. The general principle is that you directly administer 5ml of a 3.2% w/v solution of oxalic acid in thin (1:1) syrup per seam of bees in the colony.

Directly‘ because you administer the OA solution to the seam of bees. You don’t count the seams and then simply pour it into the hive. You don’t spread it across the top bars. The idea is that the bees at the top of the seam get coated in the solution and that it dribbles down through the colony, being passed from bee to bee as they feed and groom and move about.

Two seams of bees

Two seams of bees …

During this process any phoretic mites will also get exposed to the oxalic acid. Since mites are readily damaged by the OA solution they fall off and gradually drop out of the bottom of the cluster. Gradually, as it takes a few days for gravity to deliver all the corpses.

You can therefore determine whether mites were present and killed by placing a Varroa tray underneath the open mesh floor of the hive. Note that this doesn’t tell you how effective the treatment has been … for that you’d need to know the mite infestation level before treatment as well.

When to treat

In many ways this is the critical decision. As described previously, maximal benefit occurs when the colony is broodless. Ideally you want an extended cold period late in the calendar year. The colony will cluster tightly and brood rearing will slow down or stop completely.

If the cold period has lasted 2-3 weeks, even better. This will mean that some or all of the brood present will have emerged. The more sealed brood present, the less effective trickling OA solution is as a means of controlling mites.

Choose a calm, cool or cold day. I usually wait for a day with temperatures between 0 and 5°C. Much warmer than that and the cluster starts to break up or the bees are more likely to fly about as the crownboard is lifted. Windy or wet days disturb the bees (at least when you prise the crownboard off), so it’s best to avoid those.

I prefer to treat before the year end, rather than after, if I can. From a few irregular midwinter peeks into the cluster I think queens start laying earlier than most beekeepers think.

It pays to be prepared …

Trickle 2 - £1

Trickle 2 – £1

… Aesop (~620-560BC) was right, though he wasn’t talking about beekeeping. Before treating your colonies there is some preparation needed. Do this properly and it’s a doddle.

Purchase a Trickle 2 container from Thorne’s. These are a measly quid each. You’ll only need one.

Practice with the Trickle 2 container (see below).

Gently warm your pre-prepared OA solution to about 25°C. If you made it up in advance and stored it at 4°C in the fridge this will take an hour or two. The easiest way is to stand the container (preferably thin-walled … I use a well-rinsed milk carton) in a basin of warm water.

Pour the pre-warmed OA solution into a well-labelled vacuum flask. You can buy these from Tesco for £2.50 with a capacity of 1 litre. The aim here is to take everything you need ready-prepared to the apiary so the treatments take the minimum time possible.

Remember that OA is toxic. Label everything carefully, make sure children can’t get near it and don’t use it again for food/drink purposes.

That’s it … you’re ready. You’ll need a hive tool, a bee suit, thin gloves (to protect you from the OA, not the bees), your vacuum flask of OA solution and the Trickle 2 bottle. By all means take your smoker, but you shouldn’t need it.

I’ve got a 5 ml (or 25 ml) syringe … won’t that do?

Yes … but no.

A Trickle 2 bottle holds 100ml of prepared OA solution. It takes two hands to fill the bottle, but only one hand to use it. That 100ml is sufficient for 20 seams of bees i.e. two completely full colonies (assuming an 11 frame National box). In midwinter the colony is unlikely to occupy 10 seams. A Trickle 2 bottle is also pretty accurate, reproducibly dispensing about 4.6-4.8ml of liquid. That’s close enough to 5ml.

In contrast, a syringe also takes two hands to fill (and refill). However, unless it’s a 5ml syringe, it’s difficult to accurately and reproducibly dispense liquid without using two hands. A 5ml syringe gives you the necessary accuracy, but needs refilling for every seam of bees. This takes time … during which the crownboard is off and the colony is getting chilled.

I’ve done both and can assure you that the Trickle 2 bottle is much better. Just buy one. It’s only £1 and it’ll last ages if one of your association members doesn’t borrow it … or doesn’t return it.

How to use a Trickle 2 bottle

  • Remove the cap and fill to the top of the lower chamber with liquid (practice with water).
  • Replace the cap.
  • Hold the bottle with your thumb and fingers on opposite sides of the lower chamber, with the external ‘pipe’ to the upper chamber next to your palm.
  • Undo the spout about a turn.
  • Gently squeeze the lower chamber. Liquid is forced up the pipe into the upper chamber. Hold it against the light to observe this.
  • Once the upper chamber is full, stop squeezing. Excess liquid drains back into the lower chamber.
  • If you are right handed turn the Trickle 2 bottle anti-clockwise2 using your wrist and gently squeeze the bottle to dispense the liquid in the upper chamber from the spout. If you’re left handed you need to turn the bottle clockwise.

And in practice

The single-handed operation for the Trickle 2 container really pays dividends when treating a colony. You can gently prize up one side of the crownboard, hold it in one hand, administer the OA solution to each seam with the other hand and gently lower the crownboard back down … all in less time than it took me to write that.

Like this:

This is a reasonably sized colony being treated in the second week of January 3 years ago. The video is 1’45” long, but the crownboard is only open for about 50 seconds. And I was chatting with Mick Smith off camera, so could have perhaps gone a bit faster if I’d concentrated … 😉

Here’s a more detailed view of treating a small colony:

33 seconds of warmed, acidic goodness to slaughter the mites and give the colony the best possible start to the upcoming season.

Cautions and considerations

Discard any OA solution that’s not been used. Warming it will have raised the HMF levels and this may be toxic for your bees. However, read footnote 3 for another way to avoid HMF buildup3.

Wash everything carefully – the Trickle 2 bottle, the vacuum flask, gloves etc. Since the OA solution was in syrup everything gets sticky and gummed up. Clean stuff up, make sure it’s labelled and not going to be used in the kitchen and put it away until next year.

Oxalic acid kills mites, but it’s also toxic for unsealed brood. This is perhaps unsurprising considering it has a pH of 1 (i.e. very acidic) and ‘naked’ larvae aren’t protected by the tough exoskeleton that adult bees have. This is another reason to treat during a broodless period in midwinter.

In summer, swarms can also be treated with trickled oxalic acid-containing solutions before they have sealed brood. If a swarm arrives in bait hive, let it settle and start drawing comb on the foundationless frames. A day or so later treat it with oxalic acid by trickling. When I’ve done this I usually wait until late afternoon or early evening, so most of the bees are in the box. The colony obviously won’t be clustered, but the principle is the same – 5ml of syrup down each seam. Easy peasy. Effective.

Swarms have a significant mite load, so it’s well worth treating them before they rear brood and give the phoretic mites somewhere to breed.

Finally, it’s often recommended that a colony is only treated once per year with oxalic acid by trickling or dribbling. I’m not sure where this advice originates, but it’s probably wise.

‘Vaping’ vs. trickling

The discussion forums are awash with recommendations to ‘vape’ the colony, rather than trickle. Vaporisation, or more correctly sublimation, is a widely used method and has been in use for two decades. It’s currently very fashionable. I’ll write a more substantial comparison sometime in the future, but the following brief notes might be of interest.

Sublimation can be done repeatedly with brood present (though there’s no peer-reviewed evidence of efficacy) and is both well-tolerated by the colony and is not toxic to unsealed brood. It requires specialised and potentially expensive equipment, both for delivery and personal protection. You can build your own vaporiser, but shouldn’t skimp on protection for the operator. With a well designed vaporiser and hive there’s no need to open the colony to administer treatment.

In contrast, trickling requires only the Trickle 2 bottle and vacuum flask described here. Personal protection is a pair of latex gloves. It should only be conducted when the colony is broodless, should probably only be conducted once and does require the hive to be opened (albeit briefly).

You’ll be told that vaporisation is faster. It isn’t. Watch the videos above. Even my Sublimox – probably the fastest ‘active’ vaporiser on the market – takes well over a minute per colony if you take into account sealing the box, moving the generator about, unsealing the hive etc.

There are reports that sublimation is more effective, but the difference is marginal, and possibly not statistically significant. There is also a report that colonies are stronger in the Spring after sublimation, though this may be due to toxicity to open brood by trickled OA solution. If the colony is broodless this shouldn’t be an issue.

I’ve used both many, many times without a problem. Across the UK I suspect more beekeepers trickle OA, rather than ‘vape’ (a word I dislike), though the vocal ones on the discussion forums currently favour vaporisation.

What’s more important than how you deliver the oxalic acid, is that you do treat. Trickling OA solution is so easy and inexpensive that there’s no reason not to … and your colonies will be much healthier for it.

Get dribbling 😉


If the beekeeper is of a certain age you’ll hear these terms used in a different context. We’re restricting discussions here to delivering OA 😉

If you are left handed you need to turn the Trickle 2 bottle clockwise. Actually, to be pedantic, if you are left handed and holding the bottle in your left hand, turn it clockwise. It’ll make sense once you try.

3 In the previous article on preparing oxalic acid solutions Calum posted a comment on preparing the OA in water and only adding and dissolving the required amount of sugar just before use. This has the advantage that there will be no HMF buildup. OA solution in water should be perfectly stable. I’ve not done it this way, but it makes sense and might be worth trying.

Colophon

The title of this article is a twist on the term Trick or treat. This is not entirely inappropriate as Trick or treating is a Halloween (31st October … just a few days away) custom dating back – in various forms – centuries.

The modern usage, essentially North American, dates back to the 1920’s and refers to children in costumes going house to house threatening to play a trick unless the homeowner provides a treat, usually sweets or toys. In Britain these traditions date back to the 16th Century, both of children going house-to-house asking for food and of dressing up in costumes at Halloween.

Closer to home, ‘guising‘ – children in Scotland going from door to door in disguise asking for food, coins or chocolate  – dates back at least a century.

The term Trick or treat only entered common usage in the UK in the 1980’s.

 

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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.

Caution

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

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.

Conclusions

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