It’s the middle of the season 1. Hopefully, the timely application of swarm control measures such as a vertical split or Pagden’s artificial swarm, have maintained strong colonies and created additional colonies headed by new queens.
July is the month I review my stocks with the goal of:
replacing ageing queens that are unproductive
removing bad tempered colonies (though most have already been dealt with)
preparing strong colonies to exploit late season nectar flows
making up nucleus colonies for overwintering, either as backups or for sale
Of course, this type of taking stock should be a continuous process through the season, but it’s easier to start it now for the winter, rather than leaving it to the shorter days, more variable weather and less dependable nectar flows of late summer.
Two into one does go
A small hole …
Often the intention is to simply replace an old queen with a new queen. In a vertical split this is simplicity itself. Remove the queen that is unwanted and the split board, replacing the latter with a sheet of newspaper. Make one or two very small holes in the newspaper with the point of a hive tool and leave the colony to it.
Over the course of the next few days the workers will chew through the newspaper, unite amicably and set about building up the stores for winter.
A week or so after uniting I rearrange the frames, usually making space for the queen to lay in the top box with the brood below. If the colonies being united are smaller it’s sometimes possible to remove one box altogether.
There’s discussion online about quick ways to unite colonies by spraying both with air freshener. The smell – which is usually pretty awful 2 – masks the colony scent and so the colony does not fight. I’ve not done this so can’t recommend it (or, for that matter, criticise it).
Since I’ll be returning a week later to check the boxes and rearrange frames I’m happy to stick with newspaper uniting which rarely fails. Air freshener is also one less thing to carry in the bee bag.
Nucs for pleasure and profit
Five frame nucleus (nuc) colonies overwinter well if prepared properly 3. They are really useful in the early spring to make up for any winter losses, to replace colonies with failing queens 4 or to sell.
Overwintered nucs are often appreciably more expensive than those imported later in the season, or in the glut of bees that follows the swarming season.
The queen has proved herself and the nuc is available when demand is highest … at the very beginning of the season.
Whilst I would – and have – argued that it might be better to start beekeeping later in the season working alongside your mentor, there are strong economic imperatives to overwinter nucs for sale.
Splits and nucs
With a successful split (or Pagden) you now have two queens, one strong colony and one building up fast. The latter – with the new queen – can be used to prepare a nuc for overwintering, with the remaining bees and brood strengthening the original colony for the late season nectar flow 5.
It’s easy to prepare a nuc colony to take away to a distant apiary – the new queen, a frame of stores, one or two of emerging brood and a mixed frame of eggs and brood, all with the adhering bees, together with a couple more frames of bees shaken in over the top. Make up to five frames with foundation, seal them up and ship ’em off to your out apiary.
If you don’t have access to an out apiary you should ensure that the majority of the older workers are omitted when preparing the nuc, and you should add in additional young bees to help the new queen get established.
It’s also worth stuffing the nuc entrance with dead grass for a few days to enforce the ‘new environment’ on the bees.
You exclude the old foragers by giving each frame placed in the nuc a gentle shake before putting it into the box. The old bees fly off, the young ones cling on. Do the same with the ~3-4 additional frames of bees added on top before re-siting the the nuc in the apiary.
Nucs may need feeding, particularly if there’s a dearth of nectar or bad weather. Keep an eye on them. By excluding the old foragers you can feed them without the risk of robbing. However, it’s wise not to feed them for the best part of a week after making up the nuc to allow any carried-over stragglers to return. This is why it’s important to include a full frame of stores from the outset.
There’s still ample time in the season to rear new queens, so all sorts of other combinations of requeening/uniting and/or splits are still possible. For example, I’ve recently used a particular queen to requeen a colony and will split the box she came from into 2-3 nucs, all of which should build up well for overwintering.
By splitting the box after the new queen cells are raised I ensure they were produced by a well-balanced population of bees, with ample stores under ideal conditions. I think this is better than divvying up the frames from the recently queenless box and hoping to achieve the strong and balanced population in all the nucs. Inevitably some are stronger than others … or, more significantly in terms of queen cell production, weaker.
And in between all of this amateur dabbling I’ve been working with our friends and collaborators in Aberdeen on methods of Varroa control to minimise the levels of deformed wing virus (DWV) as well as starting our studies on chronic bee paralysis virus (CBPV) …
You’ve inspected your colony and discovered queen cells on one or more frames.
Queen cells …
Do you want the good news or the bad news?
The good news is that your colony is building up well and with a little careful management and luck you’ll be able to requeen them in about a month. A new, well-mated queen should ensure a strong colony going into the winter.
The bad news is that your colony is rapidly outgrowing the space it has, it’s going to need some careful management and an appreciation of the development cycle of the queen. Unless you’re very lucky the colony will swarm and you’ll be left with one, significantly weakened, queenless colony.
Result … but probably not one you want.
Swarming isn’t a catastrophe. Things can usually be rescued, albeit with an interruption to colony development and honey production. However, it should be avoided if at all possible, not least because the lost swarm might cause problems for other people.
Play cups, charged queen cells and sealed queen cells
New queens are reared in specially shaped cells that are oriented vertically on the frame. They can be anywhere on the frame, but are often located on the edge of the comb, either at the sides or along the bottom.
Play cups …
Beekeepers make the distinction between cells of different sizes, different stages of development and – sometimes, though probably less reliably 1 – the type of cell (emergency, supercedure etc.) based upon their location.
Play cups are small cup-shaped cells that might subsequently be developed into queen cells. They’re regularly present in colonies that have no intention of swarming.
~3 day old queen cell …
After an egg is laid and hatches in one of these cup shaped cells the workers start feeding the developing larvae. At the same time the cell is extended, usually becoming broader and longer. Cells at this stage of development get a large amount of attention from workers in the hive and usually end up containing a thick bed of Royal Jelly in which the developing larvae floats. These are charged queen cells.
Charged queen cell …
Finally the cell is sealed and the larvae pupates before emerging as a virgin queen. During this period, particularly just before and after being sealed, the workers often sculpt the outer surface of the cell. Shortly before eclosion a thinner, darker brown ring can appear around the tip of the sealed cell.
Sealed queen cell …
Timing is everything
Queen development takes 16 days from egg laying to eclosed (emerged) adult virgin queen bee. The egg is laid in a cup and hatches on the 3rd day. The larva is fed copious amounts of Royal Jelly until day 8 when the cell is sealed or capped. About 16 days after the egg was laid the new queen emerges.
Queen development …
There’s a little bit of variation in these timings – hours, not days – and several diagrams show the queen cell sealed on the 9th day. In my previous description of queen rearing in a queenright colony (using the “Ben Harden“ method) I’ve stated that the cell is capped on day 9. That’s a convenient number to remember as she’ll emerge a week later.
We’re off !
Under normal circumstances the colony will swarm once the new queen cells are capped. The old queen and about 75% of the workers leave the hive for pastures new.
Poor weather can delay things, but it’s relatively rare to find sealed queen cells and the old queen still in residence … unless she’s clipped which delays things by a few days. However, clipping the queen does not stop swarming, it just buys you time and restricts the distance the swarm can go.
Clipped queen …
If the colony does swarm they often end up underneath the original hive. The queen crashes ignominiously to the ground as she leaves the hive. She then crawls up the leg of the hive stand and is joined by the flying bees beneath the floor. It’s a bit of a palaver, but you can then brush/encourage them into a skep and rehive them.
An understanding of the development cycle of the queen and the swarming behaviour of colonies explains why inspections on a seven day cycle make sense. If there are no queen cells on the first inspection there is little or no chance the colony will have swarmed on a sealed queen cell within the following seven days.
Since colonies headed by clipped queens tend to delay a bit before swarming it’s usually reckoned you can inspect on a 10 day cycle. Although most of my queens are clipped 2 I inspect on a 7 day cycle as it fits better with work commitments.
What to do if you find queen cells
Don’t panic …
Correctly determining the state of the colony now will ensure you take the correct course of action.
It’s not unusual for an inexperienced beekeeper to find one or more sealed queen cells in the colony and to immediately remove them all 3.
However, if this novice beekeeper subsequently finds there’s no queen in the colony (unsurprising as she’s swarmed), no eggs in the colony (because she swarmed >3 days ago) and no young larvae in the colony (because they actually swarmed nearly a week ago) then the colony has no chance of raising a new queen without further intervention by the beekeeper e.g. by providing a ‘frame of eggs’ from another colony from which a new queen can be reared.
What I do depends upon what I find …
I check to see if any have eggs in and then pinch them flat … mainly so I can tell if more have been made since the last inspection.
Charged queen cells
The first time I discover these I usually knock them all down and leave the colony another week.
Firstly … I check that the colony is queenright and that the queen is OK i.e. still laying at a reasonable rate, not being hassled by the workers and looking healthy. If I have any concerns about the queen I’ll start some form of swarm control (see below).
Secondly … It’s imperative to destroy all the charged queen cells. I therefore shake the bees off each frame and check the comb carefully … the sides, the bottom, the various nooks and crannies.
Miss one charged cell and they’ll likely swarm within the next 7 days. Anything that looks like a queen cell gets squidged 5.
Finally … if this is the second consecutive weekly inspection with charged queen cells I’ll start some form of swarm control (see below).
Don’t repeatedly rely upon knocking off every charged queen cell week after week after week.
You will miss one … I guarantee it. They will swarm.
Destroying charged queen cells is not swarm control
This should be engraved on every hive tool sold to new beekeepers 😉
I speak from experience 🙁
Play cup or are they planning their escape …?
Sealed queen cells
They’ve probably swarmed. It’s therefore too late for swarm control.
However, I check for eggs and the queen. I might be lucky … poor weather may have prevented swarming 6. Alternatively, the presence of eggs tells me they went in the last 3 days so I have an idea of the age of the sealed cell (so can calculate when the new queen will emerge).
Ideally I like to leave a colony with a single cell I know contains a developing pupae. Although you can open and reseal queen cells (Ted Hooper describes doing this in Introduction to Bees and Honey) to check they’re occupied, I’ve never bothered.
Instead, if there are large charged queen cells present I select one, mark the frame and then destroy all the sealed cells and unwanted charged unsealed cells. I can estimate to a day or so when the queen will emerge and so know when there’s likely to be a new mated queen in the hive.
If there are eggs and young larvae but no other charged cells (rare), I’ll knock back the sealed cells and let them rear more, finally leaving them with one known charged cell after the next inspection.
This post is already too long … there are dozens of ways of doing this. Two already described in detail are vertical splits and the ‘classic’ artificial swarm. Both are pretty much foolproof if you can find the queen. Both are conservative and non-destructive … you can reunite colonies if either fails.
Vertical splits use less equipment and need less space, but involve some heavy lifting.
When a honey bee colony swarms, what proportion of the bees in the colony leave with the queen?
A simple question and one that has been addressed using elegantly simple experiments.
But swarms don’t leave without also taking Varroa mites with them 1.
What proportion of the Varroa mites in the colony leave with the swarm? In both cases partitioning refers to the proportion that remains with the original colony (bees or mites) and the proportion that disappears over the fence (or appears in your bait hive).
Why does this matter?
If you’re interested in honey from your bees the answer to the first question is very relevant. The more bees that leave, the less remain to forage … so you’ll get less honey.
If you collect swarms or use bait hives to attract them, the answer to the second question is particularly relevant as it emphasises the importance of Varroa treatment of newly-hived swarms.
Does size matter?
Colonies swarm when they are strong, which is usually – but doesn’t have to be – when the colony is big. There are a number of factors that influence swarming, but the strength of the colony i.e. lots of bees in the space available, is one of the most important. A strong nucleus colony of only 3 frames will swarm under similar conditions that induce a huge double-brooded hive to swarm; the latter might contain 75,000 bees, the former perhaps only about 7500.
In addition, because the survival of swarms is influenced by their size (see below) we need to be aware that large and small colonies may behave differently. For example, if only 5000 bees formed a ‘viable’ swarm, the 3 frame nuc described above could generate just one, whereas the double-brooded monstrosity could produce a prime swarm and loads of similarly-sized casts 2. Since swarms of all sizes are seen, it suggests a fixed proportion of the bees leave, rather than a fixed amount …
Counting the bees in a swarm
Occupied bait hive …
Counting large numbers of bees is not a trivial task. Of course, counting the bees in a swarm is pretty straightforward … catch the swarm, weigh it and divide by the weight of a ‘single bee’ 3.
But this doesn’t tell you the number of bees in the original hive. You need to know this to determine the proportion of bees that leave with the queen.
Thomas Seeley from Cornell University used an elegant solution 4 to count the size of the original colony before and after swarming. He established several 3-frame narrow observation hives between gridded glass panels. The hive was so narrow that only a single layer of bees could occupy the beespace between the glazing and the comb. By counting bees in about 10% of the grid squares, averaging and multiplying he could accurately determine the total number of bees in the colony … which was about 7600.
He determined the number of bees in the colony early every morning during the swarming season. Immediately after swarming he counted the bees remaining in the hive. By dividing the number of bees present after the swarm left with the number present that morning he could determine the proportion of the adult workers present in the swarm.
And the answer is …
When Seeley’s small colonies swarmed, 75% of the workers departed in the swarm 5. This figure is in good agreement with previous studies conducted by Getz and colleagues 6 using two larger colonies (~30,000 bees in each, 72% of which left with the swarm), and with work from the 1960’s 7 using small and large colonies (73% and 66% respectively).
Swarm partitioning therefore appears to be colony size-independent, with about 75% of the adult workers departing with the queen.
So, if size doesn’t matter, why does size matter?
A small swarm …
Juliana Rangel and Thomas Seeley went on to establish swarms of different sizes – small medium and large, containing 5000, 10,000 and 15,000 bees respectively … and a queen. The large swarms developed into fully-established colonies better (drawing more comb, collecting more nectar and rearing more brood). Most significantly, large swarms had a much higher survival rate. Almost 90% of the small or medium swarms failed to overwinter, whereas 75% of the large swarms survived.
Again, there were precedents for this … in the mid-80’s Lee and Wilson had monitored survival of natural swarms and showed that larger swarms were more successful.
So size matters for swarm survival.
This is perhaps not surprising when you consider all the ‘work’ the colony needs to do to survive the winter – draw out a large area of comb, store about 20kg of honey and rear thousands of new workers.
And, of course, size also matters if you want your colonies to spend their time collecting nectar for honey production. When a colony swarms 75% of the workforce leaves and, inevitably, the productivity of the hive is significantly reduced for an extended period.
Mite partitioning … simple maths surely?
The only mites that can leave the colony when it swarms are those that are phoretici.e.riding around the colony on adult bees. The remainder are safely tucked away in capped cells gorging themselves on pupae.
If we assume that all the adult bees are workers 8 it is a simple calculation to work out the proportion of mites in the colony that leave with the swarm … 0.75 * X, where X is the proportion of mites in the colony that are phoretic.
So, if 10% of the total number of mites are phoretic, 7.5% of the total mites would disappear with the swarm. This could explain the small colony size and frequent swarming of Varroa-tolerant feral colonies … every time they swarm, over 90% of the mites are left behind.
But … there’s always a but …
% of mites in capped cells
The proportion of phoretic mites in a colony is unfortunately not static. It fluctuates with the availability of suitably-aged larvae to infest. It is therefore influenced by the egg laying rate of the queen.
Numbers often quoted for the experimentally-determined proportion of phoretic mites range from 10-50% (or more), a range reflected in a well-established model for the seasonal reproduction of Varroa9.
Remember that the graph (right) is modelled data. In a real-world situation there will be brood earlier and later in the year. However, in a first attempt at calculating mite partitioning during swarming in May/June the modelled data is close enough to experimentally-determined data to be usable.
Predicted and real mite partitioning numbers
The extreme values from the May/June (the swarming season) predictions in the graph above indicate that phoretic mites proportions range from 15-50% of the total in the colony. A swarm containing 75% of the adult bees in the hive would therefore also leave with somewhere between 11% and 37% of the Varroa from the colony.
The higher of these figures is quoted by Thomas Seeley in his study of the frequently swarming Varroa-tolerant colonies in the Arnot Forest, though this is calculated from his own swarm partitioning studies and data from others, and was not directly measured.
However, Jerzy Wilde and colleagues have conducted one of the few studies that have experimentally measured mite partitioning in natural and artificially-swarmed colonies. Of seven large colonies (~30,000 bees) which swarmed naturally, 25 ± 9% of mites left the colony with the swarm. Using a Taranov board, 36 ± 11% of mites left the colony with the swarm fraction in the artificially-swarmed colonies.
Sublimox vaporiser …
A quarter of all the mites in a heavily infested colony is a lot of mites.
By definition, all the mites in a swarm are phoretic, so they’re easy to kill using miticides – such as those based on oxalic acid (either trickled or sublimated) – that work best on broodless colonies.
Caveats and future considerations
I have a few concerns about the Wilde study. The size of the swarms generated was significantly smaller than usual, containing only ~45% of adult workers. In addition, the initial mite-infestation levels were quite low, implying that the available open brood was unlikely to be rate-limiting in terms of mite reproduction and the phoretic period.
I’ll return to this in a future post but it’s worth remembering that the queen markedly reduces her egg-laying rate as the colony prepares to swarm. This results in fewer 5-day larvae and so decreases the opportunities for phoretic mites to hide themselves in capped cells.
Swarming colonies may actually have elevated phoretic mite levels …
Hive inspections are the preventative maintenance of the beekeeping year. Conducted properly, they include all the necessary checks to ensure all is well now and will be until the next inspection.
Inspections are an essential part of beekeeping. Beekeepers who don’t conduct inspections probably won’t be beekeepers for long … the colony swarms, goes irretrievably queenless or succumbs to disease.
Or all three 🙁
Actually, there’s another reason … I suspect that beekeepers who don’t regularly inspect colonies are more interested doing something else. They’d prefer to be playing golf or building model railways or potholing. I covered this a few months ago when discussing beekeeping principles and practice.
Shouldn’t you be inspecting your bees today?
Their enthusiasm to properly manage their colonies that is, not potholing 😉
The clue is in the name … the purpose of inspections are to maintain the colony in a productive state and to prevent things from happening that might stop this being achieved.
‘Productive’ usually means collecting nectar for honey 1, but could equally well refer to making lots of bees for nucleus colony production. Or, for that matter, maximising drone production to flood the area with good genes for queen mating.
Essentially you’re checking the colony to ensure it’s best able to do what you want it to do.
And, if there are signs that things are going awry, you’re putting in place the preventative measures that help avoid a partial or complete disaster.
Brace comb …
A beekeeping “disaster” … let’s keep things in perspective. Swarming, queenlessness, laying workers, robbing, wasps, disease, Varroa infestation, brace comb and all the rest.
Quick or thorough but probably not both
Inspections can either be quick or they can be thorough, but rarely both. The definition of the term ‘inspection’ means “looking narrowly into; careful scrutiny or survey; close or critical examination”.
Therefore, unless you’re only checking one thing, for example whether the queen cells are sealed in a queenright queen rearing colony, it’s likely that the inspection will take some time.
3 day old queen cells …
How long depends upon experience. It probably takes me ~12-15 minutes to go through a box thoroughly and I have a reasonable amount of experience and get quite a bit of practice 2. This is a snail’s pace when compared with commercial beekeepers who can conduct a pretty comprehensive inspection in ~4 minutes.
A beginning beekeeper might take significantly longer than 15 minutes to inspect a colony.
But speed is not the issue.
Why conduct inspections?
The issue – in a routine inspection – is determining the answer to at least the following five key questions (paraphrased from Ted Hooper in his Guide to Bees and Honey):
Has the colony sufficient room?
Is the queen present and laying as expected?
Is the colony building up as expected (early season)? Are there queen cells present (mid season)?
Are there signs of disease?
Has the colony sufficient stores?
All of which, done properly, takes a reasonable amount of time.
So that’s the Why? What about when and how should inspections be conducted? These need to be addressed before considering the questions above 3.
There are several ‘when’ questions to be considered. When should you conduct the first inspection of the year? When – as in what sort of day – should you conduct the inspection? How frequently do the inspections need to be conducted?
Unless you’re looking very quickly in a hive for a specific reason inspections should only really be conducted when the exposed brood aren’t going to get chilled. This means you should choose a day when the temperature reaches at least the mid-teens (°C). ‘Shirtsleeve’ weather some call it.
This influences both the timing of the first inspection of the year and – particularly early or late in the season – the time of day that the inspection occurs. On the East coast of Scotland I did my first thorough inspection this year on the 19th of April. Last year – although the winter was nominally shorter and warmer – some hives weren’t inspected until early May because there was never a suitable day.
Lots of hive entrance activity …
Use your own judgement about whether the weather is suitable for early season inspections. The bees should be flying well. This is both an indication that the weather is good enough and reduces the hive population making the condition and amount of brood easier to determine.
Hive entrance activity …
Don’t base your decision to inspect on reports you read on beekeeping discussion forums (fora?) about others with their hives bulging with brood. They may be beekeeping in a warmer part of the country. They might be in a different country altogether. It’s also worth remembering that there’s a well-documented tendency – as with online reviews – for contributors to over-exaggerate the positives (and negatives) 4.
I also wouldn’t bother inspecting on an unseasonably warm day very early in the year. It’s unlikely you’ll be able to deduce a whole lot about the state of the colony.
I’ve started, so I’ll finish …
The frequency of inspections is largely dictated by the development time of a queen bee, and to a lesser extent by the strength of nectar flow in your locality.
If a colony is going to swarm they first prepare one or several queen cells. These are capped around day 9 after the egg is laid. Once there are capped queen cells and suitable weather the colony is likely to swarm.
That means you need to inspect more frequently than every 9 days during the peak swarming period of the season – in Fife that’s an ~8 week period from early May late June. In warmer regions, or in years with atypical weather, regular inspections might have to start earlier and continue later.
Queen cells …
“Around 9 days” really means anything from 8 days, so a 7 day inspection cycle makes most sense. If a careful inspection one week fails to find evidence of queen cells being developed there’s no chance the colony can swarm for a further 7 days at least (because there are no queen cells that are sufficiently developed).
“fails to find evidence” means you have to inspect carefully. A small charged queen cup, with a day old larva and a bed of Royal Jelly will be capped 6 days later … then they’ll be off 🙂
Generally 5 a colony with a clipped queen will take a little longer to swarm, allowing intervals between inspections to be extended to up to 10 days.
However, don’t rely on this … I’ve seen them (er, mine) swarm earlier than this. Inevitably it’s you’re strongest colony and best honey producer 🙁
Relax, but don’t be complacent
Once the peak swarming season is over the frequency of inspections can be reduced. I’m usually on a two-week cycle by mid-July, with most colonies getting their last inspection in mid/late August. This coincides with the optimum time to start applying Varroa treatments to minimise exposure of winter bees to deformed wing virus.
However, remember that a strong colony can fill a super very quickly during a good nectar flow. Inspections are required to ensure the colony has enough space – for brood expansion and for stores.
How to inspect
We’re running out of space … I’ll deal with this in more detail in a future post (and link to it from here).
Essentially, because the goal is to check the state of the colony, you need to ensure that the inspection is conducted in a way that best allows you to determine this.
An agitated colony or one stirred up to be highly defensive makes inspections much harder. It’s therefore important to be as gentle as possible, to be calm and measured in your movements and to avoid jarring the colony.
Use the minimal amount of smoke possible, don’t wave your hands over the top of the frames and don’t crush bees.
And if it all goes pear-shaped, if despite your best efforts the colony gets really stroppy, if you kick a frame over on the ground, drop your hive tool into the open brood box or the smoker goes out at a critical moment 6 … close up the box and try again another day.
Swarm arriving at bait hive …
An Inspector Calls
An Inspector Calls is a play by J.B. Priestley. Set in 1912 and first performed in the mid-1940’s, it involves a man – calling himself Inspector Goole – questioning a well-to-do family about the suicide of a working class woman, Eva Smith. Over three acts it is clear that, independently, all in the family are responsible for her exploitation, abandonment, social ruin and eventual death through poisoning. “Inspector Goole” leaves, but the secrets are now out. Subsequent checks with the police and the infirmary show there is no “Inspector Goole” or recent suicides. The play ends with a phone call from the police about the suspicious death of a young woman by poisoning …
My original bee shed and the new bee shed are about 500 yards apart. There were at least eight colonies that needed to be relocated to the palatial new facility.
En route there was a precariously narrow scaffold plank footbridge, two (not particularly passively) aggressive swans, a large flooded field and a steep earth bank. Thanks to Buster, my trusty hivebarrow, none of these physical barriers were any impediment whatsoever.
What potentially caused the problem was that the apiaries were only separated by 500 yards.
Moving colonies: the usual advice
The usual advice when moving colonies is that it is OK to shift the hive less than three feet or more than three miles.
Less than three feet because the final approach to the hive involves the appearance and smell of the colony. Flying bees that have orientated to the hive in their early flights return to the general location using obvious landmarks, but make the final approach using very local features and the characteristic odour of the colony. Just moving the hive 2-3 feet doesn’t change these local features or odour, so the bees very rapidly find the hive entrance.
The bees cope very well with moving the hive forwards or backwards and slightly less well with lateral movements.
It’s worth noting that the hive entrance should remain facing the same way for this to work. If you reverse a hive it does disorientate the bees though they find the new entrance eventually. This is exploited during vertical splits to separate flying bees with the queen.
More than three miles because the maximum foraging distance is probably a bit less than three miles. Therefore, if the hive is moved further away, all of the familiar landmarks will have disappeared and the bees have no choice but to reorientate to their new location.
In practice I’ve regularly moved hives just a couple of miles without issue. These distances aren’t set in stone.
But what about intermediate distances? For example, the swan-infested, wobbly-bridged and paddy field-like 500 yards separating my two bee sheds?
The recommended solution to these intermediate distances is to move the colonies to a distant apiary (3+ miles away) for a week or so, then move them back to their final destination. The bees are forced to reorientate, do so, ‘forget’ their original location and then are forced to reorientate again to their final location.
A totally foolproof and absolutely reliable solution to the problem.
And a lot of work.
However, in high summer with good weather and a large force of foraging bees, this is the method I usually use. I’d fit insect mesh travel screens, seal up the colonies late at night or very early in the morning, move them away for a week and then repeat the entire rigamarole to get them to their final location.
Hard physical work, lots of lifting and long days 1.
Alternatively you could move them a yard a day … but that’s only practical over very short distances
Or, more accurately, only bearable over very short distances.
Flat platform …
If you’re going to attempt this incremental migration I strongly recommend a hivebarrow with a level platform. No lifting every day. Simply push it another yard across the garden … day after day after day after day.
But this is a typical Scottish Spring …
It’s cold. Very cold at times.
It’s wet. Sometimes wet rain and sometimes wet snow.
Although the colonies are building up they are still relatively small. Because of the weather they don’t get out foraging every day. When they do it’s for an hour or two at most.
With a reasonably accurate weather forecast and careful timing it is possible to take advantage of this to move colonies intermediate distances with no problems.
Early April weather …
The Easter weekend was predicted to serve up the usual depressingly poor weather we expect on Bank Holidays. Other than Sunday we were promised intermittent rain or sleet from the Friday to at least the Tuesday.
In contrast, the Thursday before Easter was good with the bees foraging well, though it cooled quite quickly in mid/late afternoon. Importantly, inside the hives, the colonies remained active … they weren’t tightly clustered. I would avoid moving bees that are tightly clustered in very cold weather 2.
Moving in day
The new bee shed was prepared with clean floors for all the colonies that were being moved. The entrances were loosely stuffed with dried grass. The tyre on the hivebarrow was reinflated and I rummaged around in the bee bag to find some ratchet straps to hold things together.
Using just a puff of smoke at the entrance to clear any lingering bees I lifted a colony off its old stand and gently placed it on the hivebarrow. I sealed the entrance with foam3, strapped the hive securely together and then strapped the hive to the hivebarrow.
I then negotiated the flooded field, the stroppy swans, the wobbly bridge across the burn and the earth bank.
Each hive was placed on the floor of the new shed and left to settle while I fetched the remaining colonies.
Moving in day …
Finally, after 45 minutes or so, I gave each colony a tiny waft of smoke through the OMF to move the bees up, gently split the brood box from the old floor and lifted the hives onto their new floors.
Hardly a single bee escaped during the entire process … and I wasn’t savaged by the swans.
Dried grass …
The hives were reassuringly heavy so had sufficient stores. Friday delivered sleet and temperatures no higher than 3°C. The bees stayed warm and snug in the shed. Saturday was particularly rubbish. Sunday was better, but the grass blocking the entrance – now drying in the breeze and weak sunshine – still restrained them. Monday was poor again … by which time they should have forgotten about the original shed. I removed the remainder of the grass on Monday. A few bees appeared, confirmed that the weather was rubbish and quickly returned to the shed.
As I write this the weather is promising to warm up in a week or so, but it’s still unsettled. Any bees venturing out in this first full week of April will be forced to reorientate. They’ll have the brightly painted landing boards to help their final approach.
Landing boards …
There are still a few more hives to move. Since I need to rearrange colonies between out apiaries for the season ahead I’ll do this by simply swapping distant colonies about.
The > (greater than) and < (less than) mathematical symbols were – surprisingly (to me at least) – first used almost 400 years ago. Thomas Harriot, in his snappily titled bestselling treatise on ‘The Analytical Arts Applied to Solving Algebraic Equations’ 4 stated “Signum majoritatis ut a > b significet a majorem quam b” and “Signum minoritatis ut a < b significet a minorem quam b”. Or something like that 😉 Since then, and particularly since the introduction of the computer and programming languages, the greater and less than symbols have been used for a multitude of other things, not least of which is as integral components of the markup tags used in HTML. This controls the appearance of text and links on the web and explains why the page title does not display properly on the tab of my Safari web browser.
The range of miticides available ‘off the shelf‘ to UK beekeepers has recently been increased by the introduction of Apitraz and Apivar.
‘Off the shelf’ because, until recently, these were only available with a veterinary prescription.
Considering the extensive coverage on this site of oxalic acid-containing miticides and more recent posts about the – regularly ineffective – Apistan, it seemed fair and appropriate to write something on the active ingredient and mode of action of these new products.
Mites on drone pupae …
Conveniently, because the active ingredient is identical, these can be dealt with together in a single post. The similarities don’t end there. The amount of the active ingredient is the same and the way it is administered is very similar. They are different commercial products; Apitraz is distributed by Laboratorios Calier, SA and sold by BS Honeybees, Amitraz is distributed by Veto Pharma and sold by Thorne’s. The strips have a different appearance and a slightly different mechanism by which they are hung in the hive.
They even cost about the same – a single packet of 10 strips (sufficient to treat 5 hives) costs £30.50 and £31 respectively for Apitraz and Apivar.
The active ingredient in both Apitraz and Apivar is Amitraz.
Yes … I find these three names confusing similar as well 😉
Amitraz is a synthetic acaricide – a pesticide that kills mites and ticks. It was discovered and developed almost 50 years ago by the Boots Co. (the drug development predecessor of the Boots the Chemist 1 found in most high streets). Amitraz is the active ingredient in a range of medicines approved by the Veterinary Medicine Directorate, including Aludex and Certifect, both of which are used to treat mange in dogs.
For completeness I should add that Amitraz used to be used by US beekeepers and was sold as a generic pesticide under the name Taktic, though this was withdrawn in about 2014. I believe that Apivar is now available as a slow-release Amitraz-containing Varroa treatment in the US.
Mechanism of action
Amitraz has to be metabolised (essentially ‘modified’) before it is active. This modification occurs much less well in bees than in mites. In fact, the toxicity of Amitraz for bees has been determined to be about 7000 times less than in mites.
Once converted into an ‘active’ form the most important mechanism of action for Amitraz is through interaction with the alpha-adrenoreceptor and octopamine receptors of Varroa2.
OK, since you asked … octopamine receptors normally bind a neurotransmitter called – rather unimaginatively – octopamine. Quelle surprise as an apiculteur would say. It’s likely that occupancy of these receptors by Amitraz triggers a series of so-called downstream events that change the behaviour of Varroa. Similarly, amitraz also acts as an agonist 3 when binding to the alpha-adrenoreceptor which normally interacts with catecholamines. This results in neurotoxicity and preconvulsant effects.
That all sounds a bit vague. Essentially, amitraz binds and activates receptors that are critically important in a range of important aspects of the Varroa activity and behaviour. Remember here that the mite is entirely dependent upon proper interaction with the bee to complete the life cycle. For example, if the mite fails to enter a cell at the correct time or doesn’t hitch a ride on a passing nurse bee for a few days, it will likely perish.
Amitraz changes behaviour and so exhibits miticidal activity. It has additional activities as well … these multiple routes of action may explain why resistance to amitraz is slow to develop. More on this later.
Usage of Apitraz and Apivar
Both Apitraz and Apivar are formulated as plastic strips impregnated with amitraz. The bees must come into contact with the strips to transmit the amitraz around the hive. Two strips are therefore placed between frames approximately one-third of the way in from each side of the brood box – typically between frames 4 & 5 and 7 & 8 of an 11 frame box. This assumes the bees occupy the entire box. If they don’t, arrange the strips in the appropriate part of the box with 2 frames separating them. Both types of amitraz-containing strips have a means of securing them hanging between the frames.
The recommended treatment period is 6 (Apitraz, or Apivar with little/brood present) to 10 weeks (Apivar with brood present). As with Apistan, treatment should not be applied during a honey flow or when honey supers are present. Further details are included on the comprehensive instructions provided with both products. There’s also a reasonable amount of information on this New Zealand website for Apivar.
This is the good bit … very, very effective. When used properly, amitraz-containing miticides can kill up to 99% of the Varroa in a colony.
Toxicity and wax residues
The good news first. Amitraz does not accumulate in wax to any significant extent. It is not wax-soluble. This is in contrast to Apistan which is found as a contaminant in most commercially-available beeswax foundation.
And now the bad news. Beekeepers also have alpha-adrenoreceptors and octopamine receptors. So do dogs and fish and bees. Although amitraz has increased specificity for the receptors in mites and ticks, it can also interact with the receptors in other organisms. Consequently, amitraz can be toxic. In fact, if you ingest enough it can be very toxic. Symptoms of amitraz intoxication include CNS depression, respiratory failure, miosis, hypothermia, hyperglycemia, loss of consciousness, vomiting and bradycardia.
And it can kill you.
Admittedly, the doses required to achieve this are large, but it’s worth being aware of what you’re dealing with. Amitraz-containing strips should be used only as described in the instructions for use, handled with gloves and discarded responsibly after use.
Multiple modes of action makes it much more difficult for resistance to evolve. But it can and does. Resistance to amitraz is well-documented and is understood at the molecular level. However, this is in cattle ticks, not Varroa.
At least, not yet, though there are numerous anecdotal reports of Varroa resistance.
I’ll deal with resistance in a separate post. It’s an important subject and avoiding it is a priority if amitraz-containing compounds are going to remain effective for Varroa control.
When you purchase a couple of packets of Apivar – enough for 10 colonies – it might feel expensive 5. However, it’s worth remembering that this is still less than the likely ‘profit’ on a couple of jars of your fabulous local honey per colony per year, which seems pretty reasonable in the overall scheme of things.
And, if you look after your colonies well, you are maximising the potential yield of honey in the future … so you’ll be able to afford it 😉
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.
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.
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