Perhaps surprisingly if the weather is still very wintery, inside your hives brood rearing has probably started 1. It’s about half way through the winter, there’s no forage available and the colonies are surviving on the stores they laid down in the autumn last year.
But now they have a few more mouths to feed … as a consequence, they’re likely to start using the stores at a higher rate.
I’ve recently written about the importance of hefting hives in the winter to judge (very approximately) how much stores they have remaining. It’s an imprecise science at the best of times, but it is important to ensure they don’t run out.
If they do, the colony will starve to death.
If the colony is feeling a bit light you need to give it sugar as soon as practical and as close to the clustered bees as possible. The most convenient type of sugar to give is bakers fondant. This is the same stuff you get on Chelsea buns. You can buy fondant in 12.5 kg blocks for about a tenner (in bulk … one-off purchases are likely to be more expensive) from wholesale suppliers.
Fondant keeps well for several years and so it’s worth stockpiling some for emergencies. Since I use fondant for all my autumn feeding as well I buy in bulk (200+ kg) every year or two and stack it somewhere safe, dry and protected from vermin (and other beekeepers 😉 ).
Feeding fondant can be as simple as cutting a thick slice of fondant off the block and laying it across the top bars of the hive. You’ll need an eke or a reversible crownboard to provide the ‘headspace’ over the colony. Replace the roof and any insulation and the colony should be OK … but don’t stop checking for the rest of the winter.
Fondant block …
Don’t be stingy and don’t delay
It’s not worth adding a measly few ounces of fondant. If it’s midwinter and the colony is already light, a couple of hundred grams is going to only last a few days.
Don’t be stingy. Add at least a couple of kilograms.
Don’t wait for a balmy midwinter day to add the fondant. Add it as soon as you realise they’re light. It won’t harm the colony to open it up for the few seconds it takes to add the block.
Wear a veil … some colonies can be semi-torpid, others can be quite feisty. How would you feel about having the roof ripped off on a grey midwinter afternoon? You might be trying to save them from starvation, but their reaction might be something a little less than appreciative 😉
Add the fondant as close to the clustered bees as possible. A small cluster cannot move far in very cold weather. Even inches is too much. There are few sights more tragic than a cluster of starved bees just a few centimetres from lashings of sealed stores or a large lump of fondant.
Finally, don’t spend ages clearing bees off the top bars with little puffs of smoke. The colony will be getting chilled and the disturbance will be worse than the loss of the few bees you might inadvertently squash under the fondant block.
Think of the greater good … speaking of which.
When I feed colonies in the autumn I simply slice a complete block of fondant in half with a spade, open it like a book and lay it on top of the colony. With smaller amounts you can use a breadknife to (carefully … mind your fingers!) cut the block up. It’s a lot easier if the block is at room temperature.
For real convenience you can pack plastic food trays with fondant, wrap them in clingfilm and take a couple with you when you visit the apiary. If needed, simply unwrap them and invert them over the top bars of the hive. Large takeaway food containers or one of the many semi-solid types of plastic packaging used by supermarkets are ideal. Tortellini packets are good and just about fit the ekes I’ve built.
Preparing fondant …
Wash them thoroughly before use rather than subjecting your bees to last nights Chef’s Special Chow Mein 😉
Finally, remove the clingfilm completely before use. Bees tend to chew through clingfilm and drag it down into the broodnest, even incorporating it into the bits of brace comb they build. Getting rid of the traces of clingfilm during the first spring inspection is a pain, and best avoided.
During irregular midwinter visits to the apiary you need to check if the hive entrances are clear and to determine whether the colony has sufficient stores for the remaining winter. The rate at which stores are used depends upon the number of bees in the colony, the strain of bees, the temperature and whether they’re rearing brood or not.
The apiary in winter …
The easiest way to ‘guesstimate’ the level of stores is to gently lift the back of the hive an inch or two, and to judge the effort required. Beekeepers call this ‘hefting‘ the hive. Colonies should feel reassuringly heavy. After all, you’re only actually lifting half the weight of the hive – the front remains on the hive stand – and if that feels light it might indicate a problem.
The hive will be full of torpid bees on a freezing cold winter day. On really cold days the wooden floor of the hive might actually be frozen onto the stand. Don’t force it and jar them. And if you can gently lift one side, don’t just drop the hive back onto the stand afterwards. Ideally you want to judge the weight of the colony without the bees being disturbed at all.
Be gentle …
However, judging the weight takes experience. Is it a lot less than last week? Is it less than it should be? In the picture at the top there are 5 hives, only two of which (those on the closest stand, and above) are comparable. You can’t easily compare hives if you have only one or if they’re not made of the same material.
But that doesn’t mean you shouldn’t try. Over time you will get experience for what feels OK, and what feels a bit light.
And if any do feel dangerously light then you need to intervene and give them more stores – in the form of fondant – as soon as possible. At least, you need to intervene if you don’t want to risk them starving to death. I’ll discuss topping up the fondant in a future post.
Technology to the rescue
You can get a much better insight into changes in the weight of a colony by, er, weighing it. Luggage weighing scales are widely available, cheap and accurate. With a little ingenuity you can fashion a means of attaching them to the side of the floor. I drilled a 6mm hole through the side runners of the floor and securely tied an eye bolt to some strong polypropylene attached to the scales.
Winter cluster …
Friendly scales …
Weighing a hive …
In a similar way to hefting a hive, lift each side carefully, but this time note the weight and add them together. It’s helpful to use scales which automagically record the maximum stable weight. Note the weight down in your hive records and see how it compares over time.
As before, be gentle with these colonies in winter. Don’t go bouncing them up and down. The bees will not appreciate it. With care you can weigh the colony and barely disturb them at all.
What? You want even more accuracy and even less work? Look at the hive monitoring equipment from Arnia, SolutionBee or others. These use under-hive scales hooked up to a mobile phone to upload weights (and lots of other data) for analysis from the comfort of your armchair.
At a price 😯
Frugal bees are better bees
Different strains of bees use their winter stores at different rates. ‘Black bees’ (Apis mellifera mellifera, or Amm) are well known for being frugal. In contrast, some Italian strains chomp through their stores like there’s no tomorrow (and if you don’t feed them, there won’t be).
My Heinz strain 1 of locally-reared bees exhibit variation in the amount of stores they use. The two comparable hives on the same stand in the top picture both started the winter packed with stores. By Christmas one of them remained reassuringly heavy, whereas the other one was feeling light and was given a fondant supplement.
All things being equal, I’d prefer my bees use less rather than more. When the time comes to rear queens later in the season the thrifty colony will be favoured.
Some beekeepers take a harder line than this … if a colony can’t store enough to get it through the winter they let it starve and so allow ‘natural selection’ to operate.
I’d prefer to have the luxury of an additional colony in Spring. I won’t rear queens from it and I’ll minimise drone brood to prevent it contributing to the next generation. Instead, I’ll build it up in the spring and then split it for nucleus colony production in late May or early June.
Unnatural selection perhaps, but it’s a solution I’m comfortable with.
Given the choice, I suspect it’s what the bees would prefer as well 😉
It’s midwinter. There’s very little to do in the apiary. Time is probably better spent planning and preparing for the coming season (and drinking tea in the warm).
However, there are a few jobs that shouldn’t be forgotten.
Let the undertakers do their work
The first job is to ensure that the hive entrances are clear. This allows bees to readily exit and re-enter the hive for ‘cleansing’ flights during warmer days. During these days the bees will also remove some of the many corpses that accumulate during the winter. If the hive entrance is clear these can be removed easily. If the entrance is blocked they continue to build up and – on warm days – you can hear a panicky roar of trapped bees from inside the hive.
Corpses at hive entrance …
Don’t worry about the loss of these bees. It’s what happens. The colony goes into the autumn with perhaps 30,000 adult workers. Four months later, at the end of December, there may be only about one third of this number remaining. Brood rearing is limited during this period (and at times non-existent), but picks up in early January.
Even assuming no brood rearing, this means that 150-200 bees a day are expiring. If they are rearing brood, even at a significantly diminished rate, it means that more than 200 bees a day are dying.
For comparison, 300 bees is about a ‘cupful’ … the number you’d do a Varroa count on. Imagine dropping a cupful of dead bees on the hive floor every day for a fortnight. Unless these corpses are cleared away the hive entrance gets blocked. This is what the ‘undertakers’ clear.
On calm warm days you can find the corpses littered on the hive roof, or in front of the entrance, dropped there by workers carrying them away from the hive.
Since ‘flying’ days may be infrequent at this time of year and/or bees have other jobs to do, like go on cleansing flights or collect water, they may not carry the corpses very far … don’t be alarmed by the numbers of corpses around the hive entrance.
Don’t count the corpses …
A bent piece of wire to the rescue
I mainly use kewl floors with a dogleg entrance slot (see the top image on this page) that reduces robbing by wasps and negates the need for a mouse guard. I’ve fashioned a simple piece of bent wire to keep the entrance slot clear of corpses on my irregular visits to the apiary during this time of the year.
Kewl floor unblocker …
I’ve only ever had problems with large, double-brood colonies after very extensive cold periods (~4 weeks with hard frosts every night) when the entrance has got blocked. One colony I managed to save despite it showing signs of Nosema after the bees were trapped for several days.
It takes just seconds to check that the entrance is clear and gives considerable peace of mind. If you use mouseguards it’s worth checking the holes aren’t all blocked after an extended cold period.
Next week I’ll discuss the other important winter check … are there enough stores remaining to stop the colony starving?
Anyone familiar with Monty Python will recognise the post title.
This was one of the well-known scenes from Monty Python and the Holy Grail, a 1975 film parody about the Arthurian legend and a low-budget quest for the Holy Grail. The film usually ranks close to the top in surveys of the best comedies of all time, with another Monty Python film (The Life of Brian) often topping the tables.
In the film there’s a further scene (A self-perpetuating autocracy) which involves a political argument with interesting parallels between the public perception 1 of a colony of bees and the biological reality. This is topical, with the recent Deloitte report on women in leadership roles holding back the careers of other women they perceive as a threat.
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 …
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‘.
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.
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 …
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 …
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 bêtenoire 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 …
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.
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 …
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 …
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? 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 …
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 😉
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.
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
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.
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.
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
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.
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 …
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.
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.
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.
We’re in the hiatus between the end of the beekeeping season and the start of the beginning of the planning for the preparation for the next. Or, I am.
Of course, if you’re reading this from Australia (G’day … the 5th largest readership globally) or Chile (Hola … 62nd in the list) then things are probably just getting really busy.
Inevitably things here are going to be a bit quiet for a few months. Have patience.
Getting ready for winter
Here in the Northern hemisphere, at a latitude of about 56°N, the nights are rapidly getting longer and the temperature is tumbling. We’ve had several sharp frosts already. I checked my bees yesterday through the perspex crownboards – where present – and most were pretty tightly huddled together. In the very warmest part of the day there were a few flying in the weak sunshine, but the majority of colonies were quiet.
Since many of the most recent posts have been rather long (and I’m pressed for time with work commitments) I’m going to restrict myself to a few brief comments about this tidy – and tiny – little hive tool from Thorne’s.
Pocket hive tool
One of the final tasks of the year is to slice off the brace comb built in places along the tops of the frames while feeding colonies. I only use fondant, usually adding 12.5 kg to start with and then a further few kilograms if I think the hive is a bit light. All this fits nicely under one of my inverted, insulated perspex crownboards. However, as the fondant it taken down and stored, the bees tend to build little pinnacles of comb under or around the plastic bag.
Before closing the colony up for the season all these bits of brace comb need to be tidied away. I simply run a sharp hive tool along the top bars of the frames, remove the wax and – eventually – melt it down in my steam wax extractor. If you leave the wax in place you can’t put the crownboard back the right way up … or, when you do, you risk crushing bees.
Bargains in the sales
In the Thorne’s summer sales this year I bought the usual range of stuff I have almost no use for, together with half a dozen of the cheapo copies of their claw hive tool to replace those I’ve lost or lent during the year.
In addition I bought a couple of their ‘pocket hive tools’ (shown above) for a quid each.
These are small and neat, have a simple frame lifter at one end and a very good, sharp, chisel tip at the other. They are made of stainless steel. They fit neatly into the palm of the hand, don’t project too far and yet are enough to provide the leverage to separate all but the most stubbornly propolised frames.
For tidying up the top bars of my hives before closing them up for year this little hive tool was just the job.
‘Pocket hive tool’ is a bit of a misnomer though. It’s certainly small enough to fit into your beesuit pocket, but just about sharp enough it won’t be staying there long. Any serious pressure, for example as you get back into the car/van/truck risks either a nasty injury ( 😯 ) or it will eventually escape through a neatly sliced-through seam.
It might be better to keep it in your bee bag, or – as I do with other hive tools – store it in a bucket of soda in the apiary.
The phrase small, but perfectly formed is at least 200 years old. Google Books first lists it in the Gentleman’s Magazine and Historical Chronicle of 1779 (though in those days they used a medial or long ‘s’ so the title was the Gentleman’s Magazine and HiſtoricalChronicle) where it appears in an article by Mr Rack describing (or deſcribing) a new found aquatic animal. Whether ‘small, but perfectly formed‘ is now an idiom or a cliche is unclear. The usually excellent Brewers Dictionary of Phrase and Fable (2014) defines the idiom as meaning “something noticeably small but compensating for this by a perfection of quality”. Their first reference to the phrase occurs in a letter written in October 1914 by Duff Cooper to Lady Diana Manners, later his wife, and quoted in Artemis Cooper’s Durable Fire (1983): ‘Your two stout lovers frowning at one another across the hearth rug, while your small, but perfectly formed one kept the party in a roar’. The expression was probably not original to Cooper but drawn from the fashionable talk of the period. The usage is often tongue-in-cheek or journalistically formulaic for anything small … which is exactly how I’ve used the term in the title of this post.
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 …
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
… 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.
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.
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 😉
1 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 😉
2 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.
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.
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:
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
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 …
Looking down on the colony from above, a seam of bees is the row visible between the top bars of the frames.
Remember to prepare ~10% more than you think you need. You’ll inevitably spill some when using the Trickle 2 bottle to administer it to the colony. It’s not that expensive, so don’t risk running out.
And the how strong? The recommended concentration to use oxalic acid at in the UK has – for many years – been 3.2% w/v (weight per volume) in 1:1 syrup. This is less concentrated than is recommended in continental Europe (see comments below on Api-Bioxal).
My advice – as it’s the only concentration I’ve used – is to stick to 3.2%.
Listen very carefully, I shall say zis only once†
A bit of basic chemistry coming up. Skip to the warning in red below and then the recipes if you want, but this explains some important things about working out how much to use.
The molecular formula of oxalic acid is C2H2O4. The molecular weight of oxalic acid is 90.03 g/mol. However, the oxalic acid you purchase – including Api-Bioxal – is the dihydrated form of oxalic acid.
Di as in two, hydrated as in water.
The molecular formula of oxalic acid dihydrate is C2H2O4.2H2O and oxalic acid dihydrate has a molecular weight of 126.07 g/mol.
Therefore the weight of oxalic acid in 1 g of oxalic acid dihydrate is 90.03/126.07 = 0.714 g.
Oxalic acid is toxic
The lethal dose for humans is reported to be between 15 and 30 g. It causes kidney failure due to precipitation of solid calcium oxalate.
Clean up spills of powder or solution immediately.
Take care not to inhale the powder.
Store in a clearly labelled container out of reach of children.
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
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
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 …
HMF is toxic to honey bees at high concentrations. Studies from ~40 years ago showed that HMF concentrations below 30 mg/l were safe, but above 150 mg/l were toxic1. HMF buildup is one way overheated honey is detected.
At 15°C HMF levels in OA solution can reach 150 mg/l in a little over a week. At room temperature this happens much faster, with HMF levels exceeding 150 mg/l in only 2-3 days. In the dark HMF levels build up slightly less quickly … but only slightly 2,3.
Only make up OA solutions when you need them.
If you must store your oxalic acid-containing syrup for any length of time it should be in the fridge (4°C). Under these conditions HMF levels remain well below toxic levels for at least one year. However, don’t store it for this long … use it and discard the excess. Don’t use discoloured oxalic acid solutions as they’ve been stored incorrectly and may well harm your bees.
Please re-read the comments above about the toxicity of oxalic acid. If you are going to store it in the fridge it must be very clearly labelled and there must be no chance that children can reach or open the container.
Api-Bioxal is the least expensive VMD-approved miticide and powdered oxalic acid is much, much cheaper. Both contain the same active ingredient, oxalic acid, which is highly effective against phoretic mites.
In midwinter, with very low levels (or no) of brood, a single oxalic acid-containing treatment minimises mite levels for the coming season.
Oxalic acid-containing solutions are easy to prepare. I recommend you make sufficient for your own colonies and those of your beekeeping friends and association members. My previous BKA used to distribute litres of the stuff for use in midwinter. Use this solution in midwinter and then discard any that is unused.
Oxalic acid-containing solutions are inexpensive and easy to administer by trickling. As I shall demonstrate next time.
Please re-read the safety instructions highlighted in red above.
† 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.
1Jachimowich T., El Sherbiny G., Zur Problematik der verwendung von Invertzucker für die Bienenfüttering, Apidologie6 (1975) 121-143.
3Prandin, 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
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:
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.
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
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 …
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.
However, I will re-present the graph that illustrates the modelled (using BEEHAVE) mite levels‡.
Time of treatment and mite numbers
The gold arrow(days 240-300i.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
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.
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.
Kewl floors (sometimes called Dartington-inspired floors) have an ‘L’ shaped entrance that I think offers advantages to the colony when defending against wasps (or robbing by nearby colonies) and negates the need for mouse guards. However, the very feature that provides these advantages – the ‘L’ shaped gap about 9mm high – also makes them liable to get blocked with bee corpses during late winter.
During the depths of the winter, with a relatively quiescent colony and winter bees that are only a couple of months old, this isn’t usually a problem. However, as the winter turns to spring and the colony starts to become active again the attrition rate increases. As the weather improves and the winter bees expire the corpses can block the entrance, trapping the remaining colony inside.
Blocked Kewl floor …
This is the sort of thing that should only happen once†. Early in the season you go and visit the apiary on an unseasonably warm and calm day. With one exception the colonies look reasonably active. Foragers are returning with pollen and there are bees setting off on orientation flights.
If you listen carefully at the hive with no activity you might be able to hear the bees panicking inside. Splitting the brood box from the floor reveals the scale of the devastation. It’s a distressing sight. If you’re lucky there will be good numbers of flying bees. If you’re unlucky the colony will have already perished or there will be obvious signs of Nosema.
Kewl floor unblocker …
With reasonably regular visits to the apiary this is a situation that can easily be avoided. Insert a piece of bent wire – I use an old bicycle spoke – in the entrance slot, turn through 90° and drag it across the full width of the entrance. The ‘vertical’ piece of the wire needs to be longer than the depth of the entrance slot on the floor, but not so long that it fouls the bottom of the frames.
† But, do we always learn from our mistakes? I’ve had this happen a couple of times. In both cases the colony was strong going into the winter and on a double brood box. The first time the colony perished, though it’s not actually clear whether they died from being trapped or from a midwinter virus overload. The second time, April 2015 (shown in the hive photo above), the colony survived. When I discovered the blocked entrance there were still lots of flying bees. I swept the floor clean and cleared the entrance, reassembled the hive and left them to it. On checking a couple of days later they were taking in pollen and I found the laying queen, none the worse for wear, at the first full inspection the following week.