It’s been a miserable wet winter in Fife … but the days are now noticeably longer (and drier), though I’m still usually driving to and from the office with headlights and wipers on. However, finally there are signs that spring is on the way. I heard my first skylark yesterday and there are drifts of snowdrops in the hedgerows …
Having moved here last summer with the expectation that the east coast would be dry but cold (remember, these things are all relative) the winter has delivered almost the complete opposite. It’s been spectacularly damp. Not only here in Fife of course. Most of the northern half of the UK has enjoyed some terrible weather, with significant levels of flooding in major cities like York. For the last three months the rain has been ~200% of the 30 year average:
The graphs above (from the excellent Met Office website) are the rainfall anomaly from the 1981-2010 average, with the darkest blue indicating at least 200% of the average. In contrast, the temperature has been at or above the average, with December being very much warmer (more than 2.5°C above the average, which is 2-4°C).
It’s not clear to me whether warm and wet winters benefit either bees or beekeepers. In inclement weather the bees can’t get out to forage – not that there’s much for them to forage on – and the warm temperatures prevent them from clustering tightly. They probably get through their stores more quickly and may continue to raise brood – inevitably this makes midwinter Varroa treatments by trickling or sublimation less effective. On the other hand, there are probably fewer losses of weaker colonies through isolation starvation when it’s too cold for them to move across the frames to the sealed stores.
However, my preference would always be for short and cold winters. It might sound heartless but I’d prefer weak colonies didn’t survive the winter as they are usually slow starting in the spring and remain unproductive – if they survive at all – through the year. Far better is to realistically assess all colonies in the autumn and unite weak ones with strong ones, boosting the latter and increasing their chances of overwintering successfully. There is no point in uniting weak colonies with other weak colonies, unless you’re stuffing three into one (and the ‘one’ is a strong colony). It shouldn’t be necessary to say it – but I will anyway – if a colony is weak because of overt disease it should not be used to ‘boost’ a strong colony … it’ll do nothing of the sort.
Colonies that went into the winter apparently strong, but dwindle rapidly and get significantly weaker may well have dangerously high levels of pathogenic viruses such as deformed wing virus. This might occur if Varroa control was left too late in the season.
Winter cluster …
Anyway, enough discussing stuff that should have been sorted out months ago … the weather is belatedly showing signs of winter, with temperatures below freezing for several nights in a row, a bit of snow here and there, interspersed with some cold, clear days. I’ve not seen a bee venturing out on a cleansing flight for days and the colonies visible under the perspex crownboards are tightly clustered. Nevertheless, there are some very obvious signs of spring, with daffodils, snowdrops and celandines flowering, the leaves unfurling on the hawthorn bushes and the willow buds just about breaking.
Drifts of snowdrops
I realise that this is mostly another ‘not beekeeping‘ post, but I thought something slightly easier than the graphs and chemistry of Varroa treatments might be welcome. With the season proper fast approaching, now is the time to make plans and to ensure everything is ready for those early season hive inspections.
Yet more snowdrops …
The title of this post is a play on the title of a poem by Stevie Smith, Not waving but drowning, in which she describes the thrashing of a drowning man being mistaken for waving. It might not have been wet enough this winter to drown, but it sometimes felt like it …
When and how do you treat colonies to have the greatest effect in minimising Varroa levels? At the end of this longer than usual post I hope you’ll appreciate that this is a different – and much less important – question than “When is the best time to treat?”.
You probably use one of the treatments licensed and approved by the Veterinary Medicines Directorate (VMD), which include Apistan, Apivar, Apiguard, MAQS and Api-Bioxal. I’ve discussed the cost-effectiveness of these treatments recently. If used correctly, all exhibit much the same efficacy, reducing phoretic mite levels by 90-95% under optimal conditions. That being the case the choice between them can be made on other criteria … the ease of administration, the cost/treatment, the likelihood of tainting the honey crop, the compatibility with brood rearing, whether they mess up your vaporiseretc. After using Apiguard for several years, with oxalic acid (OA) dribbled in midwinter, my current preference – used throughout the 2015 season – is OA sublimation or vaporisation. This change was based on four things – efficiency, cost, ease of administration and how well it is tolerated by a laying queen. The how? you treat is actually reasonably straightforward.
When, not how, is the question
OK, but what about when? Because, if the treatments are all much of a muchness if used correctly, the when is actually the more important consideration. When might be partly dictated by the treatment per se. For example, Apiguard needs an active colony to transfer the thymol throughout the hive so the recommendation is to use it when the ambient temperature is at least 15ºC (PDF guidance from Vita). It’s worth stressing that this is the ambient temperature, not the temperature in the colony, which in places will be mid-30’s even when it’s much colder outside. At low ambient temperatures the colony becomes less active, and in due course clusters, meaning that Apiguard is not spread well throughout the colony, and is therefore much less effective. If you’re going to use Apiguard you must not leave treatment too late.
For readers in Scotland it’s interesting to note that the SBA annual survey by Peterson and Gray shows significant numbers still use Apiguard in September and October, months in which the mean daily maximum temperature is ~14°C and 11°C respectively … so the average daily temperature will be well below the recommended temperature for effective Apiguard use.
However, the when should be primarily informed by the why you’re treating in the first place. It’s not really Varroa that’s the problem for bees, it’s the viruses that the mite transfers between bees when it feeds on developing pupae that cause all the problems. Most important of these is probably Deformed Wing Virus (DWV), but there are a handful of other viruses pathogenic to bees that are also transmitted. DWV causes the symptoms shown in the image above … these bees are doomed and will be ejected from the hive promptly. However, although apparently healthy (asymptomatic) bees have low levels of DWV, it’s been shown by Swiss researchers that DWV reduces the lifespan of worker bees, and that high levels of DWV in a colony are directly associated with – and causative of – overwintering colony losses. Therefore, the purpose of late summer/early autumn treatment is to reduce the Varroa levels sufficiently so that high levels of the virulent strains of DWV are not transmitted to the overwintering bees.When? therefore has to be early enough that this population, critical for overwinter survival, will live through to the spring – however long the winter lasts and however severe it is. However, before discussing when winter bees are reared it’s worth considering what happens if treatment is used early or late.
What happens if you treat early?
Mid June treatment …
For example, mid-season or after the first honey crop comes off. Nothing much … other than slaughtering many of the phoretic mites. This is what most beekeepers would call “a result” 😉 Aside from possible undesirable side effects of treatment – like tainting honey, or preventing the queen from laying or even, with some treatments, queen losses – early treatment simply reduces mite levels. It’s important to remember that the levels may well not be reduced sufficiently to negate the need for a treatment later in the season … as long as there is brood being raised the mites will be reproducing (for example, look at the mid-June treatment generated using BEEHAVE modelling – image above). Furthermore, avoiding those undesirable side effects might require some ‘creative’ beekeeping (for example, clearing the supers and moving them to another hive) and will certainly inform the choice of treatment but, fundamentally, if the mite levels are high then treating earlier than is usual will benefit the colony, at least temporarily. If the mite levels – estimated from the disappointingly inaccurate mite drop perhaps – are dangerously high you should treat the colony.
What happens if you treat late in the season?
Isolation starvation …
In midsummer workers only live for ~40 days. If mite levels are high, virus transmitted to these workers will shorten their lives, so reducing the colonies’ foraging ability and – possibly – ability to defend itself against wasps or robbing late in the season. However, if you delay treatment until very late the lifespan of bees raised at the end of the season – the overwintering bees – will be reduced with potentially more devastating consequences. The usual winter attrition rate of workers will be higher. The cluster size of the colony will shrink faster than a colony with low mite levels. At some point the colony will cross a threshold below which it becomes non-viable. The cluster is too small to move in cold periods to new stores, resulting in the beekeeper finding a pathetic little cluster of bees in a colony that’s succumbed to isolation starvation. A larger cluster, spread across a greater area and more frames, is much more likely to span an area of sealed stores and be able to exploit it.
When are winter bees reared?
In the Swiss study referred to above they looked at the longevity of winter bees. The title of the paper is “Dead or alive: deformed wing virus and Varroa destructor reduce the life span of winter honeybees”. We can use their data to infer when winter bees start to be reared in the colony and when mite treatments should therefore have been completed to protect these bees. Their studies were conducted in Bern, Switzerland, in 2007/08 where the average temperature in November/December that year was 3ºC. They first observed measurable differences in winter bee longevity (between colonies that subsequently succumbed or survived) in mid-November. This was 50 days after bees emerged and were marked to allow their age to be determined. By the end of November these differences were more pronounced. Therefore, by mid-November Varroa and virus-exposed winter bees are already exhibiting a reduced lifespan. Subtracting 50 days from mid-November means these bees must have emerged in late September. Worker development takes ~21 days, so the eggs must have been laid in the first week of September, and the developing larvae capped in mid-September.
To protect this population of overwintering bees in these colonies, mite treatments would have had to be completed by the middle of September, so that mite levels were sufficiently low that the developing larvae weren’t capped in a cell with a Varroa mite carrying a potentially lethal payload of DWV. For Apiguard treatment (which takes 2 x 14 days) this means treatment should have been started in mid-August. For oxalic acid vaporisation (which empirical tests suggest is best conducted three times at five day intervals) treatment would need to start no later than early September and preferably earlier as it is effective for up to a month.
Of course, these figures and dates aren’t absolute – the weather during the study would have influenced when the larvae would be raised as winter bees, with the increased fat deposits and other characteristics that are needed to support the colony survival through the winter. Despite the study being based in Switzerland my calculations on dates are probably broadly relevant to the UK … for example, the temperature during their study period is only about 1ºC lower than the 100 year average for Nov/Dec in Eastern Scotland where I now live.
That was all a bit protracted but it hopefully explains why it’s important to be selective about when you administer Varroa treatments. Chucking in a couple of trays of Apiguard in mid-August or mid-October has very different outcomes:
in mid-August the phoretic mite population should be decimated, reducing the transmission of virulent DWV to the all-important winter bees that are going to get the colony through the winter. This is a good thing.
in mid-October the mite population will be reduced (not decimated, as it’s probably too cool to effectively transfer the thymol around the hive – see above) but many of the winter bees will already have emerged, probably with elevated levels of DWV to which they will succumb in December or January. This is a bad thing.
Perhaps perversely, treating early enough to prevent the expected Varroa-mediated damage to developing winter bees is not be the best way to minimise mite numbers in the colony going into the winter. Using BEEHAVE I modelled the consequences of treating in the middle of each month between August and November¹. I used the default BEEHAVE setup as described previously. Figures plotted are the average of 3 simulations, each ‘primed’ with 20 mites at the start of the year.
Time of treatment and mite numbers
There’s a lot on this graph. To show colony development I plotted numbers of eggs, larvae and pupae (left axis) as dotted red, blue and black lines respectively. Mite numbers are shown in solid lines – treated with a generic miticide in mid-July (black), mid-August (blue), mid-September (brown), mid-October (cyan) and mid-November (green). In each case the miticide is considered to be 95% effective at killing phoretic mites. The gold arrowhead indicates the period during which winter bees are developing in the colony, based upon the data from Dainat.
Oxalic acid trickling
Treating at or before mid-August controls the late-summer build up of mites in the colony – look how the blue line changes direction. Mites that are not killed go on to reproduce in late September and early October, resulting in levels of ~200 at the year end. Remember that mites present in midwinter can, in the absence of sealed brood, be effectively controlled by trickling or vaporising oxalic acid (Api-Bioxal), and that this Christmas miticide application is particularly important if the autumn treatment has not been fully effective. In contrast, treating as late as October and November (cyan and green lines) exposes the developing winter bees to the highest mite levels that occur in the colony doing the year, and only then decimates the phoretic mite numbers, with those that remain being unable to reproduce effectively as the brood rearing period is almost over. Starting treatment in mid-September isn’t much different, in terms of exposing the winter bees to high mite levels, than starting later in the year.
So, within reason, treating earlier rather than later both reduces the maximum mite levels and helps protect the winter bees from virus exposure. Of course, treating as early as mid/late August may not be compatible with your main honey crop (particularly if you take hives to the heather) … but that’s another issue and one to be addressed in a future post.
STOP PRESS There is a very important follow-up article to this. Kick ’em when they’re down describes why it’s so important to treat during a broodless period in midwinter to minimise mite numbers at the start of the following year. Just treating in late summer is not sufficient … you’ll protect your winter bees, only for them to be targeted by mites the following Spring.
¹BEEHAVE makes a distinction between ‘infected’ and ‘uninfected’ Varroa, the proportions of which can be modified. This might (no pun intended) not accurately reflect the reality in the hive, where Varroa-mediated transmission of DWV results in the preferential amplification of virulent strains of the virus. I need to roll my sleeves up and delve into the code to see if the model can be altered to fully reflect our current understanding of the biology of the virus. This might take quite a while …
I’ve been dabbling with BEEHAVE, a computer simulation of a honeybee colony. It’s not beekeeping, but it’s about as close as you can get in the middle of winter. BEEHAVE was developed by Matthias Becher in the University of Exeter and the paper that describes the model is published and Open Access [PDF]. The model includes a wealth of user-modifiable variables such as forage availability, climate, beekeeping activities and pathogens, and outputs information on colony size, speed of development, age structure, honey stores etc. The BEEHAVE simulation is implemented in the open source language NetLogo and is freely available. The parameters that influence colony development – egg laying rate, drone/worker ratios, forage (nectar and pollen) availability, mite replication rate etc. are all based on measured and published data (or logically extrapolated from this if they don’t exist) so that the in silico performance is a fair reflection of what might be expected in the field.
If you can, do … if you can’t, simulate it 🙂
I’m interested in the rational and effective use of miticides to control Varroa-mediated transmission of DWV (and other viruses) in the hive. Using BEEHAVE and a standardised set of conditions allows predictions to be made of how effective a particular Varroa control might be. For example, here’s a simple question we can try and answer:
How important is a midwinter mite treatment if you’ve treated earlier in the year?
Using BEEHAVE set to all the default conditions and ‘priming’ the colony with just 20 mites on the 1st of January it’s possible to see what happens if no treatments are applied over one or more years. It’s then possible to repeat the predictions with the inclusion of a Varroa treatment. For the purpose of this brief introduction to BEEHAVE I’ve used a miticide which is applied and active for a total of 28 days and which kills 95% of phoretic mites. This might broadly reflect Apiguard treatment (2 x 14 days) or vaporised oxalic acid (OA; 3 treatments at 5 day intervals, but documented to kill mites for up to one month). I’ve additionally looked at the application of a single treatment with oxalic acid in midwinter, again killing 95% of phoretic mites, the sort of effect that OA trickling might achieve if there’s no brood present.
No treatment … they’re doomed
BEEHAVE modelling is based on a series of underlying probabilities (e.g. likelihood of a developing pupa to become mite associated, likelihood of that being a drone or worker pupa) so doesn’t produce the same results every time it is run¹. For example, the graph above shows adult bee numbers (left axis, blue lines) in an untreated colony for three simulations of up to five years each (horizontal axis), together with the associated mite number (right axis, red lines). Mite number build up strongly as new brood is reared each spring, with mite numbers peaking at ~24,000 in the fourth summer. In the third and fourth winters mite number per bee range from 2-4. The default conditions of 20 mites, coupled with a minimum viable colony size of 4000 bees, results in one colony succumbing in the fourth winter and the two remaining dying in the fifth winter (bee numbers drop to zero). Real studies – with untreated hives in the field – have shown similar outcomes (Martin, 1998 [PDF]) though colonies tend to die between winters 2 and 3, presumably because the input mite populations are higher². In all subsequent graphs the data plotted is the average of three simulations.
One treatment … better than nothing
It’s worth remembering at this point that the advice from the National Bee Unit is that mite numbers in the colony should be maintained below 1000 (Managing Varroa [PDF]). To try and achieve this we need to investigate the influence of applying miticides in the simulation – in mid-June (left graph), mid-September (middle) or late December (right). I appreciate mid-June is very early in the season, but it emphasises an important point.
Mid June treatment …
That’s a bit better 🙂 These plots show the averages of adult bee and mite numbers (using the format shown above, blue for bees, red for mites). None of the in silico colonies expired during the simulation though the mite numbers are dangerously high irrespective of the treatment during the mid/late summer months. Note that range of the scale on the right hand (mite numbers) axis differs in each graph. Treatment in mid-June (left) delays the summer exponential rise in mite numbers and, in terms of overall impact on mite numbers (and consequent adult bee losses) is measurably better than only treating in midwinter (right). Of the conditions tested, mid-September (centre) is clearly the best … Varroa levels are reduced at the same time as the colony starts to contract, leaving the remaining mites less opportunity to reproduce. Maximum colony size remains about the same year on year and Varroa numbers never reach more than one third of those seen in either mid-summer or midwinter treatments. However, not everything is rosy … Varroa levels are dangerously high from the third summer on, and levels are increasing each winter. Remember that these simulations were started with just 20 mites in the colony².
Do your colonies have only ~20 mites in them this winter?
Two treatments … a double whammy
Two optimal treatments
It’s only when you combine early autumn and midwinter treatments that mite numbers are really well controlled. Under the highly optimised conditions – both treatments were set to be 95% effective against phoretic mites – Varroa numbers remain below the NBU recommended maximum of 1000 for the duration of the simulation. Clearly the combination of the mid-September slaughter of phoretic mites, coupled with a midwinter mopping up – when there’s little or no brood present – provides really tight control of Varroa levels. However, the importance of this is perhaps even more apparent when you consider the consequences of a sub-optimal mid-September treatment.
One 85% treatment
The graph on the left shows the consequences of using a miticide that achieves only 85% efficacy … perhaps reflecting Apiguard usage when the ambient temperature is too low for the thymol to be spread throughout the colony. Under these conditions mite numbers rapidly get out of control. Compare that with the graph on the right which includes an additional midwinter treatment where mite numbers are far better controlled … though only to about the same level as is seen with a 95% knockdown of mites in mid-September (centre graph in the ‘one treatment only’ section, above).
And the answer is …
Occupied bait hive …
Although the majority of miticides are broadly similar in their maximum published efficacy, I suspect that they are often used in a way or under conditions that do not routinely achieve these maxima. For example, the 30 year average September temperature in England is just below 13°C, much lower than the temperatures in which Apiguard efficacy reached the reported maximum of 99%, and lower than the Vita-recommended minimum temperature (15°C). Therefore, the answer to the original question (which was How important is a midwinter treatment if you’ve treated earlier in the year?) is … if there’s any chance the late summer/early autumn treatment was sub-optimal then a midwinter treatment is very important to prevent Varroa levels building up in the colony, resulting in the spread of virulent strains of DWV and other viruses. The other broad conclusion is that miticides are much more effective – in terms of impact against the total mite population – when brood levels are low or absent. That’s why brood breaks coupled with miticide treatments e.g. applying vaporised oxalic acid to a recently hived swarm or one that has moved in to a bait hive, are a very powerful combination to reduce the impact of mites, and the viruses they transmit, on the colony.
There are additional considerations which influence the choice and timing of miticide treatments. In a future post I’ll address the timing of the autumn treatment and the critical development of the overwintering bees that get the queen and the colony through to the following Spring.
¹BEEHAVE provides the ability to model colony development based upon measured and measurable parameters within a honeybee colony. Of course, in the real world a host of factors influence our bees – climate, forage availability, bad beekeeping, good beekeeping, integrated pest management, swarming, queen longevity etc. These are all variable within BEEHAVE but have been left unaltered from the defaults for the purpose of this post in which only the timing and efficacy of miticide treatment was altered. All the data for this post were generated using the rather verbosely numbered BEEHAVE_BeeMapp2015 version.
²Mite levels were deliberately started at a very low level to emphasise how quickly they build up if not controlled. Running the simulations with a higher mite input simply shifts all the graphs to the right e.g. increasing input mites to 200 (not an unreasonable number for many midwinter colonies) with no treatment, results in the virtual colony dying in early December of the third year, with mite levels having reached ~5300 in the first summer and ~19000 in the second.
Like Mr. Jinks “I hate those meeces to pieces”.Mr. Jinks was talking about Pixie and Dixie, whereas I think my troubles were caused by wood mice (see photo on the right below). I checked some colonies last weekend and one of the nucs was suspiciously quiet. Upon further inspection it was clear that a family of mice had taken up residence and destroyed the colony. This is my first winter loss to rodents since I started beekeeping … and it’s my own fault. My standard, so-called ‘kewl’, floors are mouse resistant – they have an L-shaped entrance tunnel that is too narrow for a mouse to get through. I’ve used these for several years and, consequently, pretty much ignored the need for mouseguards. I’ve also overwintered many poly nucs over the last few seasons and never had an issue with rodents. Maybe I’ve just been lucky. Whatever the reason, the combination of no previous problems coupled with misplacing lots of my little-used (“When did I buy that?” and “I never knew I owned one of those”) beekeeping paraphernalia during the move to Scotland meant that I didn’t put mouseguards on any of the Everynuc poly nucs in my apiaries. These nucs have a cavernous entrance, just about the only poor design feature of these hives in my opinion.
Loads of stores
Pixie or Dixie?
I sublimated these colonies with oxalic acid (OA) on the 9th of December and had checked the removable tray a few days later … there were few if any mites, but also very little hive detritus (legs, cappings, pollen etc.). However, it was a filthy wet day (again) and I didn’t have a veil or gloves with me so left them to it. I suspect the mice moved in shortly after the nuc was treated with OA (or they’re a lot less affected by vaporised OA than beekeepers are), leaving them nearly three weeks to wreak carnage in, what was, a very strong nuc. I’ve now found the mouseguards and fitted them to the remaining nucs … better late than never.
More winter troublemakers
While we’re on the subject of hives receiving unwanted attention in the winter it’s worth remembering Woody Woodpecker. Green woodpeckers – these, not the greater or lesser spotted woodpeckers, are the ones to be concerned about – are scarce and locally distributed in Scotland, though they are spreading slowly North-East according to the British Trust for Ornithology. I’ve yet to see one in Fife. I’ve therefore not bothered wrapping my colonies in damp proof membrane or taken more drastic measures with yards of chicken wire and bamboo canes. Woodpeckers generally only damage hives when the weather is really cold, conditions we have yet to experience this winter. I’m also told it’s learned behaviour and, as green woodpeckers are usually resident, some apiaries can experience problems while others, just a few miles away, escape unscathed. If they are about and they have learned what easy-pickings are available in a hive you’d be advised to protect them – a woodpecker can quickly get through a cedar hive and usually targets the handholds of poly hives (often the thinnest part of the sidewall) though these are easy to repair.
The winter solstice seems like a good time to look back over the 2015 beekeeping year. With the day length about to start increasing, what went right and what went wrong? Back in March I wrote that my plans for the year were different from the usual OSR – swarming – queen rearing – summer flow – harvest – Varroa treatment – feed-’em-up and forget ’em routine as I was moving to Scotland in the middle of the season. Some of these things happened, though perhaps less than in a usual year.
Mid-season memories …
Spring – better late than never
Cloake board …
The OSR yielded poorly as the spring was cold and late. I didn’t even look inside a colony until mid-April. Colonies were only getting strong as the OSR flowers went over meaning that most of it was missed. The weather was unseasonably cold, with mid-May being 2-3ºC cooler than average. Queen rearing started in the third week of May and although grafting went well, queen mating was really hit and miss, with low temperatures and lots of rain lasting through May and June. On a more positive note, I used a Cloake board for the first time and was pleased with the results (I’ll write about this sometime in 2016 after using it a bit more). I didn’t use any mini-nucs this year as I didn’t want the hassle of dealing with them mid-season when moving North. Instead, I did all of my queen mating in 2-5 frame nucs, often produced as circle splits from the cell-raising colonies. This worked well … and considering the lousy weather was probably a lot less effort than using mini-nucs which would have required constant attention and lots of feeding. Using poly-nucs I could prime them with a frame of brood and a frame of stores and adhering bees, dummy them down and leave 3 frames of foundation (or wherever possible, drawn comb) ready to be used on the other side of the dummy board. Once the queen was mated the colony would build up well and if – as often happened this season – the queen failed to get mated or was lost (drowned?) during mating flights it was easy to unite the queenless unit with a queenright one, so not wasting any resources.
Go forth and multiply
Split board …
Beginners often find the coordination of colonies for queen rearing, and the apparent difficulty of grafting (it isn’t), a daunting prospect. When I’ve been involved in teaching queen rearing it’s clear that the relatively small scale approach I use (queenright cell raiser, grafting and – usually – mini-nucs) is often still too involved for the very small numbers of queens most beekeepers with just a couple of hives want. It was therefore interesting to raise a few queens using vertical splits, simply by dividing a strong colony vertically and letting the bees do all the work of selecting the best larvae, raising the queen and getting her mated. It has the advantage of needing almost no additional equipment and only requires a single manipulation of the hive (and even that can probably be simplified). Having documented the process this season I’ve got a few additional things I’d like to try in 2016 to make it even easier and to allow better stock selection. After that it will be incorporated into queen rearing talks and training.
Changes in Varroa treatment
The big change in Varroa treatment in the UK was the licensing of Api-Bioxal. Whether or not you consider the 50-fold or more cost of VMD-approved oxalic acid (OA) over the generic powder is justified is really a separate issue. Oxalic acid is an effective miticide and, if administered appropriately, is very well tolerated by the colony. Despite the eyewatering markup, Api-Bioxal is significantly less expensive than all other approved miticides. For the small scale beekeeper it’s probably only 20% the cost of the – often ineffective – Apistan, or either Apiguard or MAQS. Under certain circumstances – resistant mites, low temperatures or the potential for queen loss – there are compelling reasons why OA is preferable to these treatments. If we hadn’t been using OA for years the online forums would be full of beekeepers praising the aggressive pricing strategy of Chemicals Liaf s.p.a in undercutting the competition. Of course, if we hadn’t been using generic OA for years Api-Bioxal would probably be priced similarly to Apiguard 🙁
Sublimox in use …
I’ve used OA sublimation throughout 2015 and been extremely impressed with how effective it has been. Mite drops in colonies treated early in the season remained low, but increased significantly in adjacent colonies that were not treated. I treated all swarms caught or attracted to bait hives. Some were casts and there were no problems with the queen getting out and mated (though the numbers of these were small, so statistically irrelevant). Late season treatment of colonies with brood also seems to have worked well. Mite drops were low to non-existent in most colonies being monitored through late autumn. Colonies get mildly agitated during treatment with a few bees flying about under the perspex crownboard (you can see a couple in the image above … this was a busy colony) and a few more rapidly exiting the hive after the entrance block is removed. But that’s it. The colony settles within a very short time. I’ve seen no loss of brood, no obvious interruption of laying by the queen and no long-term detrimental effects. Sublimation or vaporisation of OA can – with the correct equipment – be achieved without opening the hive. I expect to use this approach almost exclusively in the future.
Moving colonies from the Midlands to Fife was very straightforward. Insect netting was an inexpensive alternative to building large numbers of travel screens. It’s the same stuff as Thorne’s sell for harvesting propolis so I’ve got enough now to go into large scale propolis production 😉 The colonies all settled in their temporary apiaries well and I even managed a few supers of honey during the latter part of the season.
Small hive beetle reappeared in Southern Italy shortly after the honey harvest was completed there. Che sorpresa. This was disappointing but not unexpected (and actually predicted by some epidemiologists). As I write these notes the beetle had been found in 29 Calabrian apiaries between mid-september and early December. It’s notable that there’s now a defeatist attitude by some contributors to the online forums (when not if the beetle arrives here) and – since not everyone are what they seem on the interweb – there are some playing down the likely impact of the beetles’ arrival (and hence the demand to ban imports) because they have a vested interest in selling early season queens or nucs, either shipped in or headed by imported queens. I don’t think there’s any sensible disagreement that we would be better off – from a beekeeping perspective – without the beetle, it’s just that banning imports of bees to the UK (admittedly only a partial solution) is likely to cause problems for many beekeepers, not just those with direct commercial interests. I remain convinced that, with suitable training and a little effort, UK beekeeping could be far less dependent on imports … and so less at risk from the pathogens, like small hive beetle. Or of course a host of un-tested for viruses, that are imported with them.
And on a brighter note …
Bee shed …
The new development in the latter part of the year was the setting up of a bee shed to house a few colonies for research. This is now more or less completed and the bees installed. It will be interesting to see how the colonies come through the winter and build up in spring. The apiary has colonies headed by sister queens both in and outside the bee shed so I’ll be able to make some very unscientific comparisons of performance. The only problem I’ve so far encountered with the shed was during the winter mite treatment by oxalic acid vaporisation. In the open apiary the small amount of vapour that escapes the sealed hive drifts away on the breeze. In the shed it builds up into a dense acidic hazy smoke that forced me to make a rapid exit. I was wearing all-encompassing goggles and a safety mask so suffered no ill effects but I’ll need an alternative strategy for the future.
Due to work commitments, house, office and lab moves, things were a lot quieter on the DIY front this year. The Correx roofs have been excellent – the oldest were built over a year ago and are looking as good (or as bad, depending on your viewpoint) as they did then. They’ve doubled up as trays to carry dripping supers back from the apiary and I’ll be making more to cover stacks of stored equipment in the future. Correx offcuts were pressed into service as floors on bait hives, all of which were successful.
With well-fed colonies, low mite counts, secure apiaries and lots of plans for 2016 it’s time to make another batch of honey fudge, to nervously (it’s got hints of an industrial cleaning solution) try a glass of mead and to finish labelling jarred honey for friends and family.
Soft set honey was often called creamed honey before that description was effectively outlawed – at least for labelling purposes – under the trade descriptions act because it ‘contains no cream‘. It’s the stuff that’s spoonable and spreadable, it feels like velvet on the tongue because the crystals are so fine (hence creamy) and it remains looking good for a long time. The long shelf life more than compensates for the (relatively small) effort required to produce it … you don’t have to sell it or give it away quickly before granulation takes over and the appearance is spoiled. Winter is a good time to prepare soft set honey as it requires low temperatures.
Granulated honey label
All honey granulates. At least, all honey that hasn’t been subjected to the sorts of heating and filtration used by commercial packers to produce a uniform and sometime bland product with a very long shelf life. The rate at which honey granulates is related to its composition. Honey with a relatively high glucose to fructose ratio – such as oil seed rape – granulates faster. Granulation is also influenced by temperature and particulates (e.g. pollen) that acts as a ‘seed’ for granulation. My honey carries a label indicating that granulation is a completely natural process and is a sign of high quality honey.
Soft set honey
Soft set honey is honey in which the granulation has been controlled. A small amount (~10%) of honey with a soft, fine grain, is used as a ‘seed’ for liquid honey. As the latter granulates it takes on the consistency of the seed honey. The principle is straightforward and an industrial process was patented by Elton Dyce in the 1930’s. However, this requires rapid heating and cooling of bulk honey, something most beekeepers are unable to achieve. There are some good descriptions online about making soft set honey, including a useful video by ‘BeekeeperDevon’ on YouTube. There are also a lot of conflicting methods published and some that are, frankly, either nonsense or wrong.
This is how I do it … followed by some details on a few of the critical bits.
Extracted honey should be left to completely crystallise in honey buckets. This might take several weeks. The honey, particularly if it’s OSR, is likely to be spoonbendingly hard. In the following description I’m assuming the honey has only been (at least) coarse filtered on extraction, so will almost inevitably still contain bits of wax and the odd leg or antenna.
Melt a full bucket of crystallised honey completely. For a 30lb bucket I find this takes about 24-36 hours at 50ºC in my honey warming cabinet. Stir it once or twice during this period if you get the chance – this speeds up the process. Honey should not be kept at elevated temperatures for extended periods to avoid the build up of HMF.
Cool the filtered honey to 35ºC in the honey warming cabinet. At the same time, warm the seed stock (see comments below) to 35ºC in bucket with a tap. By keeping the temperature below about 40ºC the all-important fine crystal structure of the seed stock will not be destroyed.
Add the filtered bulk honey to the seed stock. Mix gently but very thoroughly. The intention is to completely disperse the fine seed stock crystals throughout the mixed honey. You can use a stainless steel corkscrew and drill, or a honey creamer. Of the two I prefer the latter. Try and avoid incorporating air during the mixing (hence ‘gently’) to avoid frosting in the final product.
Cool the honey to less than 14ºC, mixing every 12 hours or so. It’s easy to achieve this temperature in winter in an unheated outhouse, pantry or conservatory. In the summer you can do this by adding a succession of freezer blocks to the warming cabinet (but it’s hard work). The honey will get increasingly hard to mix and will – within a week or less (and possibly within a couple of days) – set. This is soft set honey.
Re-warm the bucket of honey to 35ºC and bottle it. See comments below.
The seed stock
You need about 10% by weight of a suitable seed stock to make soft set honey. You can use more or less, it’s not critical. Much less than 5% and it won’t be enough to ensure even crystallisation, or will take a very long time to finally crystallise. More than 10% is unnecessary and you’d be better saving it for another batch of soft set honey. If you’ve not got a seed stock of a suitable consistency (by which I mean of the consistency you want your final soft set honey to have) you can make, borrow or buy some.
Pestle and mortar …
To makeyour seed stock grind hard set crystallised honey using a pestle and mortar until it has a wonderful, even consistency. It will start as hard unyielding lumps and end up with the consistency of thick toothpaste. This is hard work but you might only need to do it once, so do it well. You can borrow your seed stock from a neighbouring beekeeper who has something suitable, returning the same amount after you’ve prepared your own soft set honey. Finally, you could even buy your seed stock from a supermarket. If you insist on buying the starter, at least steer clear of the “mix of EU and non-EU” honeys (why don’t they just state “sourced from goodness knows where”?) which could have just about anything in them. You are aiming to produce a top quality product. The type of honey you use as your seed stock is immaterial; it will only comprise a small amount of the final product, the consistency is what matters.
Bottling soft set honey
At 35ºC the prepared soft set honey will barely flow through the honey tap. However, with a little effort, and a long handled spoon to gently stir it, the thixotropic honey can usually be made to flow sufficiently to get it into jars. Again, to avoid frosting try not to mix air into the honey; hold the jar just under the honey tap with the bucket slightly inclined.
Keep about 3lb of your first batch of soft set honey – I use these useful sealable plastic containers – to use as the seed for your next bucket. This might be the following week or the following year – I’ve just used up the last of my 2014-prepared seed stock. If you’re preparing batch after batch of soft set honey on a weekly basis you can simply leave the seed stock in the bottom of the bucket with a tap. I’ve found silicone spatula spoons really useful for mixing honey, for getting the last few ounces out of the honey bucket and for quickly removing all the honey from the last three 1lb jars after you realise you’ve just bottled the seed stock for the next batch 😉
The majority of my full colonies are on kewl floors. Some call these ‘floors with underfloor entrances‘, which is a bit more of a mouthful. These floors have narrow ‘L’ shaped entrances; the bees are forced to access the brood box through a 8-9mm high or wide slot, negotiating a 90º bend en route. For the majority of the season these offer more than enough advantages to easily outweigh their slightly more difficult construction (though you can buy something broadly similar if needed). These advantages include:
integral (and readily replaceable) Correx landing board
no need for mouseguards – even determined mice can’t negotiate an 8mm right angle
guard bees can occupy both the landing board and brood box entrance so far fewer problems with robbing or wasps (and if these are really a problem a simple 9mm lathe can be pushed into the entrance leaving a single bee gap at one end)
bees can be confounded by the gap under the landing board when reorientating to these floors, though there are quick’n’dirty fixes to this and it’s only ever an issue for a few days. For the same reason, clipped queens might – on returning to the hive – miss the entrance and end up underneath the floor (though this happens with floors and normal entrances)
during long cold winters the entrance can become blocked with bee corpses – the only really significant problem and easily avoided
There can be a high loss of bees from the colony during long cold winters. This is generally not an issue during the depths of winter, but as the weather warms slightly and the colony becomes more active – and, inevitably, the overwintering bees get older – the attrition rate rises. If the weather still isn’t warm enough for the corpses to be removed they can end up blocking the entrance. Twice in recent years I’ve had colonies trapped inside. In both cases these went into the winter as strong double-brood colonies and – due to work commitments – weren’t checked for 4-6 weeks in late January-early March. In both cases I managed to save the colonies, but they were severely stressed by the situation, with signs of Nosema, and needed mollycoddling for several weeks at the start of the season proper.
Fortunately there’s an easy solution. On your weekly apiary winter checks (or however frequent they are) push a bent piece of wire into the entrance, turn it to project up through the vertical part of the entrance slot and slide it along the full width of the hive to ensure the entrance is clear. Any old piece of wire should be suitable as long as it it short enough not to foul the bottom of the frames. For a few years I used an easily-lost piece of wire coat hanger. More recently I added a handle to a stainless steel bicycle spoke … with a little hook so it can hung up in a “safe place” (which, of course, is no guarantee whatsoever that it won’t be lost 🙁 ).
With the days getting shorter, the weather worsening and the bees hunkering down until the spring there’s little to do in the apiary. The warm weather, weekly inspections, swarm collection and queen rearing are months away … and it feels like it 🙁 However, things are already happening in the fields that hint at the season to come. The winter-sown oil seed rape (OSR) has been through for at least a month and is now 4-6″ tall. There’s a field just outside the village with acres of the stuff and it will be good to watch it develop into a sea of yellow next spring.
I have a few colonies well within range of this field, as do at least a couple of other beekeepers. Using a Google Maps Area Tool I measured the field at about 17 hectares. Although primarily self-pollinated there’s evidence that the yield and quality (i.e. the percentage that germinates) of OSR seed or its oil content, are all increased if honeybees are present at a density of about 2 colonies per hectare. So, ample to go round for the colonies I’m aware of in the immediate vicinity. Furthermore, if colonies are located close to the OSR field boundaries, honeybees forage for a considerable distance across the field – certainly hundreds of metres. This is in contrast to wild pollinators – like solitary bees and bumble bees – which tend to decline in density away from the field margins (see also this recent paper which reports the same thing; PDF). Whilst this is a compelling argument for wide, species-rich field margins and smaller fields, the reality of modern farming is unfortunately very different. However, the benefits of honeybees (and for honeybees) mean that it might be worth having a chat with the farmer and moving a few colonies onto the field.
OSR honey isn’t to everyones taste and it certainly involves more work for the beekeeper. It must be extracted soon after the supers are collected or it crystallises in the comb. In addition, unless it’s converted into soft-set or ‘creamed’ honey it will inevitably set rock-hard in the jar, resulting in many bent teaspoons. On a more positive note, the availability of large amounts of pollen and nectar relatively early in the season helps colonies build up strongly. With good weather it’s an ideal time to replace comb, getting the bees to use the OSR nectar to build brand new comb – perhaps on foundationless frames – free of diseases for the season ahead. A great way to start the year.
My recent comments on the cost of Api-Bioxal prompted me to look in a little more detail at the cost of miticides routinely available to beekeepers. The figures quoted below are the best prices listed by one of three leading beekeeping suppliers in the UK (E.M. Thorne, Maisemore’s and C. Wynne Jones – there are lots of other suppliers, but I’ve used these three and been satisfied with their service). I made the following assumptions: the beekeeper is purchasing sufficient to treat three single-brooded full colonies for three years (i.e. something with a reasonable shelf-life) with as little left over as possible. Costs per colony treatment were calculated for 9 colonies (3 x 3 years) only … any ‘spare’ can therefore be considered as free. This means that for Apiguard, available in packs of ten trays (5 colony treatments) or a 3kg tub (30 colonies), the cost is calculated per colony from two packs of 10 trays as a full course of treatment for one colony requires two trays. Obviously, buying in bulk – for example through a co-operative purchasing scheme in your beekeeping association – should reduce these costs significantly. No postage costs were included.
Apiguard – two boxes of 10 trays (C. Wynne Jones) = £41 = £4.55/colony
Apistan – two packs of 10 strips (C. Wynne Jones) = £41 = £4.55/colony
MAQS – one 10 dose tub (all suppliers) = £57.60 = £6.40/colony
Oxalic acid (OA) crystals – one 300g tub (Maisemore’s) = £4.32 = £0.48/colony
Note that this simplistic comparison hides a number details.
These various treatments should be broadly similar in their efficacy (see below) in reducing the mite population, but must be used according to the manufacturers instructions for maximum efficiency. Under optimal conditions all quote at least 90% reduction in mite levels. However, Apistan (and Bayvarol, not listed) is pyrethroid-based and resistant mite populations are very widespread. In the presence of totally or partially resistant mites, Apistan will be of little or no benefit. Interestingly, Apistan resistance (which, like resistance to pyrethroids in other species, is due to a single amino acid substitution, so readily selected) appears to be detrimental to the mite in the absence of selection. This means that it may be possible to use Apistan effectively every 3-5 years as part of an integrated pest management as long as other beekeepers in the area follow the same regime. During the years Apistan is not used the pyrethroid-resistant mites should reduce in number, so restoring the efficacy of the treatment. I’m not aware that this idea has been properly tested, but it might be worth investigating.
Only the first four treatments are approved for use in the UK by the VMD.
Both the oxalic acid-containing treatments – Api-Bioxal and OA crystals – require preparation before use, or specialised equipment for delivery. OA vaporisation (sublimation) also necessitates both care and personal protection equipment to prevent exposure to the chemical which is a lung irritant. The costs indicated do not include these additional requirements.
The treatments are not equivalent or necessarily interchangeable. For example, a) only MAQS should be used when honey supers are present, b) Apiguard is moved around the hive by active bees, so treatment is recommended when average daytime temperatures are above 15ºC , and c) there are reports on discussion forums of repeated OA vaporisation treatment – 3 at 5 day intervals – for colonies with brood present. The costs indicated above assume a single treatment (in midwinter or of a swarm/shook swarm in the case of OA) with any of the listed compounds.
Finally, the ‘excess’ amount spare after treating the colonies over three years differs significantly. The first four have sufficient left over for one further treatment. The OA crystals will have enough left over for a further 190 colonies … and buying a 300g tub is probably about the most expensive way to purchase OA per gram 🙂
Bang for your buck
As indicated above, all of the Varroa treatments listed should give 90+% knockdown in mite numbers if used properly. This means following the manufacturers’ instructions – in terms of dose, time and duration of application. A key point to remember is that the mite is only susceptible when outside the capped cell and that 80% or more of the Varroa in a colony at any one time will be inside capped cells if there is brood present. For this reason, it is preferable to treat during natural (or induced e.g. a shook swarm) broodless periods. It has even been suggested that the midwinter OA treatment should be preceded by destruction of any brood present. Although this makes sense, I can understand why some beekeepers might be reluctant to open a colony to destroy brood in the middle of winter. There have been numerous reviews of individual and comparative efficacy of the various Varroa treatments – for example this well-referenced article on mite treatment in New Zealand from 2008. If used properly there’s little to choose between them in terms of efficacy, so the choice should be made on the grounds of suitability, convenience and cost.
‘Suitability’ is a bit of a catch-all, but requires you broadly understand how and when the treatment works – for example, Apistan is a pyrethroid so works well against sensitive mites, but is pretty-much useless against resistant populations, and resistance is widespread in the UK. ‘Convenience’ is generally high in the ready-prepared commercial treatments – it takes seconds to insert a tray of Apiguard – and much lower if the compound has to be prepared or you have to get dolled up in protective gear. In this regard, the absence of a pre-mixed liquid version of Api-Bioxal is a disappointment. Thorne’s still supply (at the time of writing) Trickle 2, a very convenient pre-mixed 3.2% w/v OA treatment for mid-winter trickling, but for how much longer? Similarly, the gloves, mask, goggles and power needed to treat a colony by OA sublimation makes it far from convenient for a single treatment.
Closing thought …
1 lb jar of honey …
Despite the great differences between the cost/treatment/colony it’s worth noting that even the most expensive is not a lot more than the price of a 1 lb jar of top quality local honey … just like the stuff your bees produce 😉 So, in the overall scheme of things, Varroa treatment is relatively inexpensive and very important to maintain colony health and to reduce overwintering colony losses.
See also Managing Varroa (PDF) published by the Animal and Plant Health Agency
When I moved to Fife this summer I didn’t have space properly arranged in advance for my bees – poor planning I acknowledge, but there were quite a few other things I was juggling with at the time. The garden at the new house was just about big enough for a bait hive but I had a number of offers from friends and I had a plot provisionally agreed for my research apiary. However, until these various sites were ready I accepted a generous offer from my local association to ‘squat’ in one of their shared apiaries.
Shared apiary …
This worked very well … I dumped the majority of the hives and nucs early one morning after driving up overnight in mid-July and pretty-much left them to it. The weather in July was very poor, but August picked up considerably. In the intervening period I had to move a few nucs up to full size boxes, I treated for Varroa by OA vaporisation and I fed them up for the winter on fondant. I even got a small amount of honey from a couple of the colonies during a good flow in August. In the meantime I prepared other apiaries, in particular the space for my research colonies. This included a “bee house” – a substantial shed with holes cut in the wall – in which some colonies were to be housed.
Double brood …
With winter fast approaching and the hives at about their heaviest since they’re now packed with stores (D’oh! … more poor planning) the apiaries were finally ready and I spent a few hours moving colonies about. Buster, my trusty hivebarrow, proved invaluable when shifting colonies. As usual I underestimated the time (yet more poor planning – theres a pattern emerging here) it would take to seal up the entrances, strap the hives together, load them into the car, drive the 15 or so miles separating the temporary and new apiaries and unload everything … meaning I was left moving the last hives in the dark. Note to self: remember that bees are attracted to light when removing the entrance block and wearing a head torch 🙁
Entrance block …
As an aside, the majority of my hives have so-called underfloor entrances, which are sometimes called kewl floors, in which the aperture is a very narrow slot. The easiest way to securely seal these is to make a simple ‘L’ shaped block from softwood, nailed or stapled together, with one piece of wood a full 18″ long (i.e. spanning the full width of the National hive). This can be simply slotted into the entrance and held in place with a couple of short screws at either end … totally secure and foolproof. These are also useful when using OA sublimation, and are certainly faster and more secure than using a hive tool to wedge foam into the entrance.
And that’s more or less the end of the beekeeping year as far as I’m concerned. I have a few more hives to move and a couple of nucs to squeeze into the bee shed. After that it’s just a case of jarring some honey for Christmas, making another batch of mead, reviewing the season and planning for 2016.