Tag Archives: autumn

Those pesky mites

DWV symptoms

DWV symptoms

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

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

Infested arrivals

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

Out, damn'd mite ...

Out, damn’d mite …

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

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

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

Treat ’em right

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

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


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

Last of the drones

At the inspections last weekend there was only one colony with obvious numbers of drones present. We’ve had nearly a full month with no appreciable nectar flow and the colonies have almost all ejected the drones. Here’s one of the few that were left:

Last of the drones

Last of the drones

 

Not long mate until you too are chucked out during the autumn purge. Watch your back!

This colony was a swarm that was attracted to a bait hive in early June. I don’t know whether bee genetics influences the time when drones are ejected from the hive, but it’s notable that almost all the other queens in the apiary are half sisters (unrelated to the queen from the swarm) and there wasn’t a drone to be seen in half a dozen hives. The other notable thing about this colony is that the Varroa levels remain stubbornly high despite three treatments by sublimation. I’m just starting a second series of treatments to get the numbers down to a more acceptable level.

No, not really …

Was it good for you? … No, not really.

I recently posted the weather forecast for the week beginning the 15th of August. I was pleased that the forecast was for near-perfect queen mating conditions – sunny, warm and calm – as I had three colonies which should have contained virgin queens that were due to emerge a few days before.

The forecast was very accurate. Conditions were wonderful. I wasn’t around as I had disappeared to Torridon and Skye for a few days. On checking the colonies at the end of the week after I returned, all three contained queens at least two of which were laying.

Beinn Eighe

Beinn Eighe …

All good then …

Well, not entirely, because mid-afternoon on the previous Wednesday I’d been sent an email from my friend at the apiary that read … “Incredible roaring noise attracted me outside the workshop – a swarm moving west through the garden and into the trees.  All caught on camera”. I didn’t receive the email as I was in the howling wilderness. Not that I could have done much about it.

A very quick inspection of the colony in question on my return confirmed that they’d swarmed. D’oh! I’d obviously missed at least one additional queen cell (mistake #1) on the last inspection and a large cast (the queen must have been a virgin as the original queen had been removed from the colony) had disappeared over the fence … mistake #2. There was a queen present but bee numbers were significantly down. I closed the colony up and disappeared on business for a further three weeks … mistake #3.

The weather had been great the entire week I was away in Torridon. I suspect the colony swarmed on the Monday or Tuesday, that it hung around in a nearby tree until the Wednesday while the scout bees found somewhere more desirable to relocate to, and that my friend had seen it leaving the neighbourhood that afternoon.

Lessons learned

  1. Don’t let the colony decide how many queens should emerge. Instead leave only one known charged (occupied) queen cell to emerge. I’d left an open queen cell on a marked frame, but had not returned a few days later to check that a) it was safely sealed and b) that they hadn’t raised anymore. They had 🙁  Consequently they swarmed when the first queen emerged, leaving one or more additional queens to emerge, fight it out and then head the now much-depleted colony (see 3, below).
  2. Leave a bait hive in or near the apiary, even if the main period of swarming has passed. I’ve been very successful with bait hives over the years, successfully attracting my own and others’ swarms. In this instance the main swarming period was well-passed and I’d packed away my bait hives until next Spring. Wrong. Had I left one near the apiary I may well have managed to attract the swarm and so a) not lost the bees, and b) not potentially inflicted the  bees on someone else. I view bait hives (and queen clipping) as part of being a good neighbour.
  3. Don’t leave a weakened colony late in season. On returning from my three week absence for work I discovered the colony had been robbed out and destroyed. Clearly it had been unable to defend itself from robber bees or wasps and had perished. I should have instead made an executive decision on discovering the colony had swarmed and probably sacrificed the virgin queen and united the weakened colony with a strong colony nearby. In retrospect this was an obvious thing to do … the colony was weak, wasps were beginning to be a problem, there was little or no nectar coming in and the weather was uncertain. As it turned out the weather was good enough for queen mating while I was away. However, the combination of a dearth of nectar, a weakened colony and strong neighbouring colonies meant that robbing was inevitable and – for the colony in question – catastrophic.
Skye ...

Skye …

Had I thought carefully about things in mid-August I may have been able to prevent the inevitable carnage when the colony was robbed out. In my defence I’ve only been around for a day or two over the last month, with extended periods out of the country on business. Nevertheless, this was clearly a case of a lesson (or three) learned the hard way …


† If you’ve not read Tom Seeley’s outstanding Honeybee democracy about how a swarm decides where to relocate to you should.

What was that?

Zoom. Having moved back to Scotland in mid-2015 this is my first full season keeping bees here. The season has been very short. Some colonies weren’t inspected until the end of April and now, about 14 weeks later, it’s turned distinctly autumnal over the last week or so in Fife. Nectar flows have pretty much dried up, nights are much cooler and thoughts turn to preparing colonies for the winter. However, good winter preparation with strong, disease-free colonies and low Varroa levels means that, should Spring 2017 be early, the bees will be ready to take advantage of it.

The immediate priorities are to:

  • protect colonies from robbing
  • ensure colonies have enough stores
  • remove any honey for extraction before the bees use it

Robbing b’stards

Entrance reducer ...

Entrance reducer …

The very best way to protect colonies from robbing – either by other bees or wasps – is to keep them as strong as possible. Wasps can be very troublesome in the autumn. Smaller colonies and nucs are particularly susceptible to attack and can be devastated in just a day or so if not properly looked after. A block of foam or wood can easily be pushed into place on a full hive, reducing the space the bees need to defend. The underfloor entrance of kewl floors (right) have the added advantage of a narrow L-shaped tunnel that can be defended on the landing board and/or immediately below the frames.

It’s not unusual to have 2-4 frame nucs in mid-August, either being prepared for overwintering or with ‘backup’ queens while re-queening other colonies. If the colonies aren’t really strong enough to defend themselves they need to be given all the help they can. Reducing the entrance space to a single bee width helps a lot, particularly when the entrance is as cavernous as the design on the Thorne’s Everynucs that I use.

Reduced entrance ...

Reduced entrance …

Stores

There’s still sufficient time for strong nucs to be built up to occupy a full hive, but they need to be given sufficient space for the queen to lay and will probably require feeding unless there’s a good late-season nectar flow. This nuc (below) started the first week of July on just a frame of emerging brood, a frame of stores and a new queen and is just about ready for a full hive. Although not obvious from the picture, the feeder on the left contains a large block of fondant which the bees are busy with. This was added as soon as the flow stopped and before the nuc got dangerously light. The bees might have survived but the queen would have slowed or stopped laying eggs and development of the colony would have been retarded. This nuc is fast running out of space and will be moved into a full hive in the next day or two.

5 frame nuc ...

5 frame nuc …

The  integral feeder on these Everynucs has space for about a kilo of fondant. Here’s another nuc started a fortnight ago with a ‘backup’ queen that was also light on stores. The parent colony were showing signs of replacing the queen so I removed her and a couple of frames of emerging brood and left them in the corner of the apiary with the entrance stuffed with grass (to deter the flying bees from returning to the original colony). After a couple of days I removed the dried grass and they’re now ticking along nicely. As they’re a smaller colony and contain predominantly young bees they lack a strong force of foragers and so need regular feeding. If the original colony successfully rears a new queen I’ll have a spare for overwintering. If not I’ll unite them back together at the end of the month.

Nuc with fondant ...

Nuc with fondant …

This is the same nuc as shown in the top image with the reduced width entrance. One of the advantages of feeding fondant is there’s no chance of slopping it about and leaving spills to attract wasps to the apiary.

The image above also shows a ‘crossbar’ I add to the Everynuc feeders; this prevents the frames sliding backwards when the nucs are in transit between apiaries. The integral feeder is useful, but it means there’s no ‘stop’ against which the end of the frame topbar can rest. There is a stop fitted across the bottom of the face of the feeder (shown in a previous post) but my experience is that the inevitable jolting of a car journey means the frames lift above this and then can slide about too much with the risk of crushing bees.

Supers off

I’m resigned to it being a poor summer for honey this season – a combination of a late spring and consequent slow colony development, variable weather during the summer and an extended queenless period for many colonies due (again) to lousy weather for queen mating. Clearers are now on the majority of colonies with filled supers. I’ll retrieve all the filled frames for extraction and make up new supers with the leftovers (incompletely filled or too high water content). The latter will go back onto strong colonies, either in the hope of a late season top-up from the himalayan balsam or for winter stores.

Clearers on ...

Clearers on …


The opening video clip was from the second series of Fawlty Towers first shown in 1979. Immediately before it Basil and Sybil are discussing their early married life …

Basil Fawlty … “Seriously, Sybil, do you remember, when we were first manacled together, we used to laugh quite a lot?”

Sybil Fawlty … “Yes, but not at the same time, Basil.”

Just retrieving the clip from YouTube means I’ll now be spending half the evening chuckling over other bits of this classic series.

Basil Fawlty … “Well… may I ask what you were expecting to see out of a Torquay hotel bedroom window? Sydney Opera House, perhaps? The Hanging Gardens of Babylon? Herds of wildebeeste sweeping majestically…”

Beekeepers’ holidays

It can be tricky balancing the annual cycle of beekeeping activities with maintaining family responsibilities and domestic bliss. At least, I’m told I find it tricky 😉  Holidays, in particular, are problematic. I’m talking here about beekeepers’ holidays not beekeeping holidays, which are an entirely different thing. Many of the standard “family holiday” periods overlap with key events in the beekeeping calendar … and because the latter is influenced by the weather, it’s difficult to predict a few days ahead, let alone the 6-9 months that appear to be required to arrange a fortnight’s yacht charter in the Bahamas§.

Mallorcan market honey and (sort of) observation hive

Mallorcan market honey and (sort of) observation hive

With good weather, colony build-up is going to be full-on in April, and in a really good year you can be starting queen rearing at Easter if it is late in the month. May is when the swarming season starts … and ends in June, just in time for the “June gap” to start which (in a bad year) might require colonies to be fed. The summer months of July and August are busy with the main flow, preparing colonies for the heather or harvesting (and possibly more queen rearing). September means Varroa treatments should be applied and colonies should be fed syrup or fondant for the winter. And then midwinter is interrupted by oxalic acid treatment (or Api-Bioxal if you’re the type of beekeeper who can afford Bahamian cruises), checking stores etc. And almost all of the timings above can be plus or minus at least a fortnight to take account of the vagaries of the weather.

February and November might be provisionally free … which creates another weather-related problem. Firstly – if honey sales have gone well during the year (and they’ll need to have been good as the 90m Athena is an eye-watering $350,000/week) – you’ll not want to be going island-hopping in the Bahamas in November as it’s still the hurricane season. Secondly, if your knees are as bad as many beekeepers’ backs, skiing in February might be a non-starter even if snow is available.

Less is more …

… likely to avoid you losing a swarm. The duration of the family holiday is also an issue. Inspections really need to be conducted at 7 day intervals during the main part of the season – say late-April to late-July. A fortnight away can mean missing the development of queen cells which are capped on the ninth day, at which point the prime swarm with your queen and foraging workforce disappear over the apiary fence. Not only do you return to a rather emptier hive, but your chance of a good honey crop has just been significantly reduced. You can increase the inspection interval to 10 days if you clip your queens, but that’s still four days short of the fortnight.

Queen rearing, from colony preparation, through grafting, cell raising and getting the virgin queens mated, takes about a month and – although not hugely time-consuming – is very-much time-critical. Getting to your cell raiser a day late might mean you have a box with one virgin running about and a pile of virgin queen corpses.

Apiary in Andalucia

Apiary in Andalucia

Nevertheless, with a little preparation, an appreciation of colony development and your fingers firmly crossed it is possible to get away during the beekeeping season without too many problems.

Holiday solutions

It seems to me that there are three obvious solutions …

  1. Go between late autumn and early spring, to the southern hemisphere if you’re after some warm sunshine. Or to Aspen or Whistler for the skiing if your knees are up to it.
  2. Get a friend to look after your colonies and go whenever you want. Depending how well behaved your colonies are, or the state you find them in on your return, this might only work once per friend 😉
  3. Accept that some beekeeping activities will be interrupted, prepare well and go for a week.

My knees are a bit dodgy and I get more than enough long-haul with work commitments so option 1 doesn’t work for me. I’ve avoided option 2 as I either have too many colonies to think it’s reasonable to foist upon a beekeeping friend, or they’re so badly behaved I’m too embarrassed to ask. So option 3 is the only choice … which is why I didn’t post anything last week as I was enjoying the walking in the Serra de Tramuntana in Mallorca.

Benjamin Franklin was right

Bait hives ...

Bait hives …

By failing to prepare you are preparing to fail. Sneaking off for a week just as swarming period was kicking off, with the best weather of the season predicted to arrive and the OSR in full flower, might have been asking for trouble. However, a little time spent on preparation helped avert disaster. Bait hives were put out near the apiaries. Remaining overwintered nucs were unceremoniously dumped into a full hive. Any colonies looking even vaguely crowded were given lots of additional space and almost all were on double broods by the time I left. Every full colony was given one additional empty super. Where necessary, one or two frames stuffed with stores were removed and replaced with foundation or drawn comb. Finally, all colonies were checked for queen cells and other obvious signs of swarm preparation the day before I left.

Nine days later I returned … none of the bait hives had been occupied, none of the colonies had swarmed, almost all of the colonies were doing precisely what they should have been doing which was building up strongly and filling the supers. Two in the bee shed were doing particularly well, having almost filled several supers. Pretty much everything was under control with the exception of one queenless colony that, the day before my departure, had been given a frame of eggs and young larvae but had failed to make any decent queen cells.

During my absence the weather in Fife was excellent … in contrast, I walked into this lot in the Tramuntana …

Thunderstorm overlooking the Bay of Pollenca

Thunderstorm overlooking the Bay of Pollenca, Mallorca …

Despite not going on a beekeeping holiday, it’s still possible to see – and sample – some of the local beekeeping activities, as shown in the photos at the top of the page from Mallorca and Andalucia taken in previous trips.


§ I wish

 Just in case you’re thinking of buying bees from me please note that this is a rather poor joke 😉

As an aside … I’ve never seen an area with more hornets that this region of Southern Spain

Time to BEEHAVE

BEEHAVE ...

BEEHAVE …

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

No treatment

No treatment

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.

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

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.

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

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.

This is the second in a series of related posts about Varroa control. The first was on drifting in honeybees. I’ve created a separate page that lists these and other posts on the how, why and when of Varroa treatment.

Use them or lose them

Colonies with queen problems at this time of the season are unlikely to get through the winter. It’s therefore better to identify these early enough to try and rescue the situation. Having completed my Varroa treatment I check colonies to determine whether they have a laying queen. If the colony is piling in the pollen, bulging with bees and has few, if any, drones I don’t even bother to open the box. In contrast, a colony with any of the following signs gets a more thorough check:

  • little or no pollen being taken in … remember this might be because there’s none available, another example of where comparisons between colonies are useful
  • slow to take the fondant down (or syrup, though I only now use fondant for autumn feeding), but not because the box is obviously already stuffed with stores
  • lots of drones (almost all of these should have been evicted by now), indicative of a drone laying queen
  • an obviously weak colony

With a perspex crownboard you can detect all of these without disturbing the bees or opening the box.

I checked the colonies in one of my apiaries as I’d noticed two that were causing some concern at the final OA vaporisation treatment. One had a good level of stores, but the colony was weak and there were no eggs, larvae or sealed brood. The clipped and marked queen – mated earlier this year – was still present but had clearly failed* and, this late in the season, there was no chance of the colony replacing her. The bees were otherwise fine, with no signs of disease, well tempered and were well worth saving.

Rescuing the situation

I disposed of the queen and united them over newspaper with a strong colony on a nearby hive stand. In a few days I’ll put a clearer board under the upper brood box, then rearrange the frames of stores to leave the remaining box packed. Any spare frames of stores – and there should be at least half a dozen – will be used to boost other colonies.

Uniting over newspaper ...

Uniting over newspaper …

Of course, I’m not really saving these bees at all. Instead I’m using their potential to strengthen another colony, so maximising the chances of getting the recipient colony through the winter. With no brood of any sort in the colony it’s likely the queen failed at least 3 weeks ago. This means that the bees present were unlikely to be ‘winter bees’ and would therefore be expected to perish over the next few weeks. However, in the meantime, they will help strengthen the recipient colony – enhancing it’s ability to raise new brood and increasing the pollen and nectar collected as the season winds down.

Nearly ready

Nearly ready

The second colony was weaker than I’d have liked, but – reassuringly – there were 2-3 frames of brood in all stages, together with an unmarked and unclipped queen. Since all the queens in the apiary were clipped and marked earlier in the season this was clearly a supercedure queen, raised in the last few weeks. The colony was beautifully calm so I gently closed them up. My bee house will be ready soon, so I’ll make sure this colony is one of the first to occupy it. The additional shelter should help them through the winter. With the new queen laying well and the weather set fair for the rest of this week, there’s a good opportunity for the colony to build up before they’re moved.

* Remember … some Varroa treatments can cause the queen to stop laying. For example, Apiguard is tolerated by some queens but not others who can stop laying for two or more weeks. The colony with the failed queen (above) had not been treated with Apiguard so I was pretty sure she was a dud.

Sublime sublimation

Sublimox vaporiser

Sublimox vaporiser …

Sublimation is the conversion of a substance in the solid phase into the gas phase without going via the intermediate liquid phase. With suitable heating oxalic acid (OA) powder can be converted into a vapour which, when spread through the hive, provides a quick and effective way to reduce the mite levels … hence it’s often referred to as oxalic acid vaporisation (or vaporization … if you search the web on this topic you’ll find at least four variant spellings). With too much heating OA decomposes to formic acid and carbon monoxide, so the temperature of the vaporiser is critical to generate the optimal cloud of OA vapour (or vapor!). I’ve been using a Sublimox vaporiser this season with good results and provide a description of the machine and its use here.

Vaporisation vs dribbling

Most beekeepers are familiar with midwinter treatment with 3.2% OA solution (in syrup), applied by ‘dribbling‘ 5ml per seam across the clustered colony. Under these conditions the colony needs to be broodless as a) it’s not effective against mites in capped cells and b) the OA dissolved in syrup is toxic to brood. It’s also reported that the ingested OA may be suppress subsequent brood rearing, at precisely the time the colony should be getting started for the upcoming season. Vaporisation or sublimation avoids this toxicity … the OA is introduced to the hive as a gas which permeates the entire colony, recrystallising as tiny crystals on all surfaces – bees, comb, internal walls etc. Studies of OA vaporisation has shown it is ~95% effective in reducing phoretic mite numbers. I recommend you read the extensive coverage by Randy Oliver @ Scientific Beekeeping who covers efficacy, mode of action and toxicity (though I’ll return to this last bit later).

Sublimox vaporiser

This is an active vaporiser which blows a jet of vaporised OA through a small (8mm) nozzle. The machine consists of a handle, a box of electrickery (which I’ve not opened) and a heating pan surrounded with a safety guard. The machine is rated at 230V AC and 300W so you need either a car battery and inverter or a suitable generator (which is what I use). The vaporiser is simplicity itself to use. One gram of OA powder is placed into a small plastic ‘cup’, the preheated vaporiser is inverted and the ‘cup’ engaged with the heating pan. The nozzle is pushed through a hole in the hive body and the vaporiser is inverted again (so it’s now the correct way up – see the top photo on this page). The OA drops into the heating cup, immediately vaporises and is blown through the nozzle into the hive. It takes 40-50 seconds to use all the OA, at which point you can move on to the next hive.

This video shows the effect of dropping a few millilitres of water into the heating pan … it’s almost exactly the same when using OA, but less likely to cover my camera with a fine dusting of OA crystals 😉

Preparing the hive

Entrance block

Entrance block …

To fill the hive with vaporised OA it’s important that as little as possible leaks out during the short period of treatment. I use a Correx Varroa tray underneath the open mesh floor. In addition, the kewl floors I use are easy to block using a simple L-shaped piece of softwood (I use these when transporting hives; when screwed onto the front of the floor there’s no danger of bees escaping). Part of the beauty of OA vaporisation is that the hive does not even need to be opened. I’ve drilled 9mm holes just above the open mesh floor level, through either the side or back of my floors. This is a better location to insert the nozzle of the Sublimox as there’s space under the frames to allow the gas to spread evenly and quickly throughout the hive. This is easier than the alternatives of using an eke with a suitable hole in it, or drilling through the side wall of the brood box (this is too close to the frames and you get poor spread of the gas – I’ve tried this on hives with a perspex crown board and it’s very obvious).

With a standard floor you could use a simple entrance block with a suitable hole in it. The nozzle gets hot … keep it away from poly hives or nucs! I treat my Everynuc poly nucs directly through the (cavernous) front entrance which I block using a thick piece of wood with a 9mm hole through the middle.

Preparing the beekeeper

OA vapour is pretty unpleasant and causes significant irritation to the eyes and lungs if exposed. Take care. You will need suitable eye protection and a mask of some sort. I use standard (and very inexpensive) safety goggles and a 3M dust/mist mask. You should also wear gloves when handling OA. It’s also wise to stand upwind of colonies being treated and to take care not to breath in any OA vapour that leaks out of gaps in the hive.

In use

I’ve treated four swarms this year using OA vaporisation. Three had very low mite levels, but the small churchyard swarm dropped several hundred mites in the 2-3 days following treatment. I don’t routinely count the mite drop on each day post treatment (I have a life) but have noticed it can increase over the first 2-3 days and then tails off over the following week or so. In large scale studies in Europe 95% efficacy was reported with mite drop continuing for up to a fortnight. There are a number of useful references on the Scientific Beekeeping site if you want to follow this up further.

I’ve also used OA vaporisation on almost all my colonies this autumn, instead of Apiguard treatment. If the colony has sealed brood the usual estimate is that at least 80% of the mites are occupying capped cells. These mites are unaffected by OA vaporisation (until they emerge) and it is therefore necessary to perform repeat treatments. Taking account of the life cycle of the mite and empirical measurements made by Hivemaker reported on the Beekeeping Forum, three treatments at five day intervals are required to have the maximum effect. Ideally this should be on a day or at a time when most of the colony is ‘at home’ … though the crystallised OA continues to be effective for several days after initial treatment. Fortunately, OA vaporisation has little or no effect on the queen, unlike many other mite treatments. The colony gets mildly agitated during treatment but calms down again within minutes and resumes foraging. In the colonies I’ve looked at after treatment there appears to be no gap in egg laying (I’ve also treated casts with virgin queens that have gone on to mate successfully). This is ideal for the autumn treatment when you want the colony to raise as many bees for overwintering as possible. In contrast, Apiguard regularly stops the queen from laying.

And finally …

There are other OA vaporisers made, and instructions on the web for a variety of DIY items – some looking more dangerous (to the operator, not the mite) than others. The majority of these are passive vaporisers, in which the OA is placed in a cool heating pan which is then placed on the floor of the colony and heated up. I’ve not used this type. They have the advantage of being less expensive and only require a 12V supply. However, they are slower to use as the pan takes longer to heat up and then needs to be cooled in a bucket of water between applications. They are also incompatible with the kewl floors I use and I presume – depending on how hot they get – with poly hives and nucs. I think the efficacy of the two types is supposed to be broadly similar.

I listened to Bob Smith talk at the MSWCC conference last week on shook swarms. I sat there thinking that a shook swarm followed shortly afterwards by a single shot of OA vapour would give a colony a really good opportunity to build up well, free of pathogens that have accumulated in the comb and free of the majority of phoretic mites and their viral payload.

Economics

The Sublimox vaporiser is not inexpensive. It costs about €380 from Icko Apiculture. This is a lot, but is about the same as three 3kg tubs of Apiguard (C. Wynn Jones list this at £87 a tub at the time of writing) which is enough to treat 90 colonies with two treatments per colony. In contrast, OA dihydrate powder in bulk (not from Thorne’s) is about £20 for 5kg … enough for 1250 colonies (assuming 4 treatments per colony – 3 doses in the autumn and one midwinter). For beekeeping associations, particularly those with large shared apiaries when treatments could and should – see a later post – be coordinated, it might be a very good investment.

 

MSWCC 2015

DWV symptoms

DWV symptoms

I spent last Friday and Saturday attending the Midland and South West Counties Convention at the Royal Agricultural University, Cirencester. It was a good venue for a meeting, complemented by an interesting and entertaining programme of talks. I presented our research on the influence of Varroa on the transmission of pathogenic strains of deformed wing virus, together with brief coverage of both high and low-tech solutions that might be useful in mitigating the detrimental impact of the mite on the virus population (and hence, the colony).

Queen rearing course

Queen rearing course

On the Saturday I donned my beekeepers hat (veil?) and discussed queenright queen rearing methods – a talk really aimed at encouraging beginners to ‘have a go’. I’m was aware there were people in the audience who earn their living from bees whereas I largely dabble at the weekends, and that they’ve probably forgotten more about queen rearing than I’m ever likely to learn. I’m always (silently) grateful they don’t ask tricky questions or interrupt with a “You don’t want to be doing that …” comment. I think only about 10% of beekeepers actively raise queens – by which I mean select suitable larvae and generate ‘spares’ for increase, sale or giving away. Without more learning how relatively easy it is to raise queen we cannot hope to be self-sufficient and will remain reliant on imported stocks, of largely unknown provenance (and with an unknown pathogen payload), particularly at the beginning and end of the season. There were excellent presentations on the analysis of pollen in forensic studies (Michael Keith-Lucas) and the use of the shook swarm (Bob Smith), together with a very interesting mead tasting event. I unfortunately missed the workshops and the Saturday afternoon presentations as I had to waste hours hanging around for three delayed trains to eventually get to Heathrow a few minutes after my flight back to Scotland departed 🙁

The MSWCC 2016 event will be running again next year (on the Gower) in mid-October hosted by Swansea and District BKA. The theme is “Meet the Natives” and – if this year is anything to go by – it promises to be a very worthwhile event.

I love the smell of propolis in the morning

[to paraphrase Lieutenant Colonel Bill Kilgore] … actually, I love the smell of propolis more or less anytime. During the quiet winter period the warm, spicy scent of propolis is a lovely reminder of hive inspections during warmer times. It’s one of the characateristic smells I associate with beekeeping, along with the lemony scent of the alarm pheremone – something best avoided – and the pretty rank smell of brood frames sterilised in the steam wax extractor (definitely best avoided).

Clearer boards

Clearer boards …

A couple of night ago I extracted the summer honey collected by the bees since moving to Scotland. There were only a small number of supers to extract; many of the colonies I brought North were nucs and have only recently moved up into full boxes, coupled with it being a rather poor summer. I’d added clearer boards under the supers the day before removing them then stacked the supers on top of my honey warming cabinet for a couple of days until I had time to do the extracting. By keeping the supers warm – the temperature in the headspace above the top super in the stack was only about 30ºC – the honey is much easier to extract than when cold and viscous.

The other effect of warming the supers is that the propolis softens and then sticks to just about everything it comes into contact with. The frames in these supers hadn’t been moved for 6-7 weeks and were heavily propilised to the runners and each other. Inevitably, prising the frames out and manhandling them in and out of the extractor meant my hands got covered with propolis. Like cooking with onions, the smell of propolis lingers well into the following day, irrespective of how well you wash your hands.

It’s been a rather poor second half of the season and many of the frames were uncapped. However, the honey – even when warmed – couldn’t be shaken out of the frames indicating that the water content was low enough to not ferment (and when measured it was almost all about 17%). The honey was sufficiently runny to filter through coarse and fine filters directly into 30 lb honey buckets for storage before jarring. This is the first honey produced by my bees in Fife and I’ll have to get some new labels designed that correctly lists its provenance.

Fondant block and Apiguard

Fondant block and Apiguard

Finally, before disappearing for a few days to  Andalusia I added a queen excluder and an empty super to every hive to accommodate a 12.5 kilo split block of bakers fondant. This is a really easy way to feed colonies up for the autumn. They take the fondant down more slowly than they would take thick (2:1 w/v) syrup which I think ensures that the queen has ample space to keep laying – these will be the important winter bees that get the colony through to the next season. It also doesn’t seem to encourage either robbing or wasps – perhaps because there’s nothing to spill. It’s also a whole lot easier to prepare … just slice a block in half with a breadknife. I simply add the fondant face down over the queen excluder, reduce the entrance if the colony isn’t at full strength, close them up and walk away*.


 

* I also added a tray of Apiguard to a couple of colonies as the first stage in autumn Varroa treatment. The majority of the colonies are going to receive vaporised oxalic acid but I wanted to do a side-by-side comparison of the effect on queen laying, so two colonies in one apiary received Apiguard.