Tag Archives: winter

Avoiding disaster

Top view of Kewl floor

Top view of Kewl floor

Kewl floors (sometimes called Dartington-inspired floors) have an ‘L’ shaped entrance that I think offers advantages to the colony when defending against wasps (or robbing by nearby colonies) and negates the need for mouse guards. However, the very feature that provides these advantages – the ‘L’ shaped gap about 9mm high – also makes them liable to get blocked with bee corpses during late winter.

During the depths of the winter, with a relatively quiescent colony and winter bees that are only a couple of months old, this isn’t usually a problem. However, as the winter turns to spring and the colony starts to become active again the attrition rate increases. As the weather improves and the winter bees expire the corpses can block the entrance, trapping the remaining colony inside.

Blocked Kewl floor

Blocked Kewl floor …

This is the sort of thing that should only happen once. Early in the season you go and visit the apiary on an unseasonably warm and calm day. With one exception the colonies look reasonably active. Foragers are returning with pollen and there are bees setting off on orientation flights.

If you listen carefully at the hive with no activity you might be able to hear the bees panicking inside. Splitting the brood box from the floor reveals the scale of the devastation. It’s a distressing sight. If you’re lucky there will be good numbers of flying bees. If you’re unlucky the colony will have already perished or there will be obvious signs of Nosema.

Kewl floor unblocker ...

Kewl floor unblocker …

With reasonably regular visits to the apiary this is a situation that can easily be avoided. Insert a piece of bent wire – I use an old bicycle spoke – in the entrance slot, turn through 90° and drag it across the full width of the entrance. The ‘vertical’ piece of the wire needs to be longer than the depth of the entrance slot on the floor, but not so long that it fouls the bottom of the frames.


 But, do we always learn from our mistakes? I’ve had this happen a couple of times. In both cases the colony was strong going into the winter and on a double brood box. The first time the colony perished, though it’s not actually clear whether they died from being trapped or from a midwinter virus overload. The second time, April 2015 (shown in the hive photo above), the colony survived. When I discovered the blocked entrance there were still lots of flying bees. I swept the floor clean and cleared the entrance, reassembled the hive and left them to it. On checking a couple of days later they were taking in pollen and I found the laying queen, none the worse for wear, at the first full inspection the following week.

 

 

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.

Everynuc feeder

I bought a few of these Ashforth-style feeders when I standardised on using Everynucs from Thorne’s a year or two ago. They’ve sat more or less unused since then, largely because the design of this poly nuc – a Langstroth-sized box adapted to take National frames – includes an integral feeder. This year I’ve used these nucs for queen mating and holding ‘spare’ queens when undertaking swarm control. Most of these have either migrated up to a full colony or been returned to the original hive, but I have a few left to take through the winter. These are now being fed up for the coming months. All are, or will be, housed in the bee shed overwinter for additional protection, though I’ve previously overwintered colonies in them outside reasonably successfully.

Everynuc feeder ...

Everynuc feeder …

Syrup and paint

The feeder is well designed, with an opening at one end leading to a good-sized reservoir for syrup or fondant. The volume of the reservoir is a little more that 3.5 litres when filled to dangerously near the brim. When using syrup – which I don’t – there’s a folded wire mesh screen that should prevent the bees drowning. They can climb up and over the dam to reach the syrup, but don’t have free access to the reservoir. This should reduce that distressingly high ‘body count’ sometimes seen with badly designed feeders. Additionally, the mesh screen prevents bees from leaving the hive when the clear plastic crownboard is removed to top up the reservoir. Convenient  🙂

Rodent damage ...

Rodent damage …

Like all poly hives, and particularly poly feeders, these should be painted before use (remember, Do as I say, don’t do as I do … some of mine aren’t painted due to poor planning). Syrup soaks into the poly if the surface isn’t sealed first. This can lead to problems with fungus growth and attack by rodents when the feeders are stored. As an aside, I try and remember to seal the entrances of my poly hives when not in use to prevent mice from destroying them … they seem very enthusiastic about having polystyrene chip parties at my expense. A couple of my poly bait hives have already been attacked this autumn – these just smell of bees and propolis (and now strongly of mouse 🙁 ) without the added attraction of syrup residues which would just make things worse.

The wire mesh screen on the Everynuc feeders is a bit ‘springy’ and probably needs holding in place with a couple of drawing pins (see image above). Additionally, both sides of the dam wall should also be painted and, when still wet, sprinkled with sand to improve the grip for bees accessing the syrup (as I show on the landing boards on my kewl floors).

Fondant

Feeder with fondant

Feeder with fondant …

At one end of the feeder, opposite the syrup reservoir, is a well that can be filled with fondant if the wire mesh screen is fitted. My crude measurements suggest it should hold about 1.5 kg of fondant if packed in tight. It might be possible to directly carve off suitably sized lumps from an intact block but it’s easier to pack it with a variety of offcuts and squeeze them down. Bees are be able to access the fondant from underneath and adjacent to the dam wall. As with syrup, feeding them like this means the fondant can be topped up without bees escaping.

Alternatively (and see the next section) you can simply stuff a big lump of fondant into the well of the feeder and omit the wire mesh – as shown above.

Easy top-ups

Easy top-ups …

I had a few concerns about how well the bees would access the fondant through the mesh – might the fondant dry out too quickly, would access be restricted as the fondant block shrank in size etc? Therefore, before it got too cold I set a couple up of feeders with or without the mesh fitted to see how readily the bees could access and take down the fondant (this post was started in mid-September). Both methods seemed to work fine though I suspect feeding through the mesh directly above the frames is likely to work better as the weather cools further, simply because it’s less far for the bees to travel and likely to be a little bit warmer.

Alternatively

Peter Edwards has recently written a short article in BIBBA’s Bee Improvement on modifying the Miller-style feeder supplied by Maisemores for their poly nuc. He simply drilled a series of ~25mm holes through the bottom of the one side of the feeder, leaving the other side unbutchered for delivering syrup if needed. A simple but effective solution ideally suited to Maisie’s double-sided feeder. Since I’m so wedded to the use of fondant for my autumn/winter feeding I may do this on a few of these Everynuc feeders as well … accepting that they’ll be trashed for use with syrup.

That’s all folks

The last week has seen temperatures peaking in the low teens, with the first overnight frosts of the year. Active beekeeping is effectively over for the season. Colonies checked at the end of last week are taking fondant down well and two that I briefly inspected had reasonable levels of brood in all stages, wth the queen laying at a consistent rate albeit much less than earlier in the season. These new bees will help the colony get through the winter and – because mite treatments were completed several weeks ago – will have been reared in a hive with very low Varroa levels, ensuring they are protected from virulent strains of deformed wing virus. I have a couple more colonies to check in the next few days and one more nuc to move to the bee shed.

However, before the autumn tidying and winter tasks are started there’s still some reasonable weather to get out and enjoy the beautiful Fife countryside.

Ballo Reservoir and West Lomond

Ballo Reservoir and West Lomond

 


 The Ashforth-style feeder has the entrance at one end or side, the feeder with the double entrance in the middle is the Miller feeder.

 

Fife’s fondant mountain

A little later in the year than usual due to work commitments …

In late August 2014 I described how I feed my bees fondant in the autumn. It’s a simple, quick, clean and efficient way to feed colonies. Additionally, I’m reasonably convinced that there are advantages for the bees as well as the beekeeper. The advantages (over syrup, either homemade or Ambrosia for example) are numerous:

  1. Readily available, pre-packed and very easy to store.
  2. Ready to use … just unbox it, slice it open and add to the hive.
  3. Addition takes only a minute or two per hive.
  4. Compatible with many Varroa treatments (Apiguard and sublimation are two I’ve used at the same time as feeding fondant).
  5. No spillages (during preparation or delivery) so far less risk of attracting wasps or getting into trouble in the kitchen.
  6. No need for specialised equipment such as Miller or Ashworth feeders that need to be stored for the remaining 11 months of the year.
  7. It’s taken down and stored better in cold weather (than syrup) as evaporation of excess water isn’t needed.
  8. You can get later brood rearing as the brood nest isn’t packed out with syrup (possibly, see below).

Point 8 is perhaps debatable. This is my impression having used it for several years, though I’ll admit to never conducting a proper side-by-side comparison. Fondant is certainly taken down more slowly than syrup. A full block (12.5 kg) might take 4-5 weeks, though it can disappear much faster. Since the water content of fondant is not wildly different from honey it takes about the same amount of storage space. In contrast, even thick syrup (2:1 sugar to water by weight) needs to be concentrated by the bees, requiring more temporary storage (where the queen might be laying or you might want her to lay to raise those all-important winter bees), reasonable temperatures and more energy.

Don’t take my word for it …

Peter Edwards of Stratford BKA used to have a posting on feeding fondant but I’m reliably informed it’s disappeared in a website revamp. He was a strong a advocate of the ease and benefits of using fondant … so don’t think that this is just my crackpot idea. Actually, it’s not his crackpot idea either … it’s not crackpot at all. And there are very few new ideas in beekeeping.

I’ve used nothing but fondant for winter feeding for at least 5 years. I’m not aware of any problems doing this. My overwintering colony losses are satisfactorily low and almost always attributable to issues other than feeding. Like a Mac, “It just works.

How to feed fondant

Open the box and slice the block of fondant in half. There are two easy ways to do this:

  1. Use a strong breadknife in the kitchen. Cover the opposing faces with clingfilm. The idea here is to stop the fondant ‘fusing’ back together as you transport it to the apiary.
  2. Use a nice sharp spade in the apiary … forget the finesse, just stomp down hard and cut the block in two. Don’t worry about the few bits of mud and grass that get included.
Neater but harder ...

Neater but harder …

In both cases leave the plastic wrapping on and don’t cut right through it … the idea is to open the block out like a book and place it face down onto the top of the frames. I used to leave the queen excluder in place but generally only do this if there’s a reason I might need to inspect the colony again (with care you can lift the QE and fondant off together). The plastic wrapping on 5 sides of each half block stops the fondant drying out.

Finesse ... nul points ...

Finesse … nul points …

A block of fondant is about 20 x 20 x 32 cm. You’ll therefore need to work out a way of providing sufficient ‘headroom’ under the crownboard. The easiest way is to use an empty super. Alternatively, where I’ve got insulated perspex crownboards, I invert them over a simple eke allowing me to see how fast the fondant is used and top it up as necessary. If, like me, you consider hive insulation important leave this in place under the roof. If I’m using a super to enclose the fondant I try and use a polystyrene one for the same reason.

Poly super and fondant ...

Poly super and fondant …

I usually remove the empty  bag when I do the midwinter Varroa treatment, or before if they’ve finished it (in which case I might add another half block or so if ”hefting the hive’ indicates it’s still a bit light). The bees usually build some brace comb on the top of the frames extending into the bag. Just gently smoke them down and scrape it off, or leave it there until the Spring.

The end is nigh

Feeding the colony up for winter marks the end of the practical beekeeping season for me. I usually experience a mixture of sadness that it’s over again for the year, together with anticipation of what’s to come the following season. With the exception of a few nucs and some colonies in the bee shed, inspections and any sort of regular checks on the colonies are over. The summer honey harvest has been taken – hopeless this season unfortunately – and Varroa levels have been monitored and minimised.

Nevertheless, winter preparations such as feeding the colony up, uniting weak colonies which are unlikely to overwinter well, protecting the colony from mice or woodpeckers and hammering down the Varroa levels are some of the most important activities of the year. If done successfully there’s every reason to look forward to having strong, healthy colonies to start the following season.


You can purchase fondant from bakers and wholesale bakery suppliers such as Fleming Howden. The price I paid – thanks to a friend in the East of Scotland Beekeepers Association – was  £10.55 for 12.5 kg. Ordering in bulk – for example via a co-operative purchasing scheme through your local association – makes a lot of sense and will reduce (or remove altogether) the delivery costs. Single blocks purchased from your local baker might cost 50% more than the price I’ve quoted. Sugar prices vary on the commodities markets … in 2013 I paid about the same as this year, but in 2014 paid only about £9 a box.

BFP wholesale used to sell fondant and had regional outlets (Tamworth in the Midlands and Livingstone in Scotland) from which collection was possible. However, although they have gone into administration, I saw one of their lorries on the way to the office this morning and it appears that the Leeds and Livingstone branches may have been bought and remain operational.

 If you have the storage space it makes sense to buy in bulk. Keep it dry and away from wasps, rodents (and other beekeepers) and it has a shelf life of at least three years. You’ll also find it useful for a mid-winter boost, for feeding mini-nucs when queen rearing, for blocking queen cages and for Chelsea buns 😉

Bee shed inspections

A brief update on how things have been progressing in the bee shed. This is my first full season keeping colonies full-time within a shed or building though I’ve successfully overwintered mini-nucs in an unheated greenhouse in the past.

Under construction ...

Under construction …

When installed at the end of last season there was almost no need to open the hives, so it’s only this Spring that the pros and cons of the bee shed have begun to be properly understood.

The colonies are completely enclosed with simple tunnels leading to exits on the East/South East face of the shed. All the colonies are housed in standard National cedar boxes or poly nucs. Other than clear perspex insulated crownboards, there is no additional insulation and the shed is not heated. The shed is situated in open parkland with woodland and arable land nearby containing good forage and there is a permanent water supply nearby.

Colony development and Varroa loads

Colonies went through the winter in single National brood boxes, fed with fondant and treated with oxalic acid by vaporisation in September (before moving them to the shed) and in midwinter. The first inspection was conducted in late March. Colonies were building up well and were significantly stronger than colonies headed by sister queens in the same apiary or in my other apiary. Between late February and early May colonies dropped only 3-4 mites in total, with Varroa boards located within pull-out trays in the hive floor. I’m sure I missed a few mites, but doubt it was very many. We’ve recently uncapped a full frame of drone brood – each cell uncapped individually – and found no Varroa present. Mite levels are therefore reassuringly low – for reasons to be discussed in a future post – with no signs of DWV-related disease.

Varroa tray ...

Varroa tray …

Since mid-April colony development has been very good and they are now on double National brood boxes with 2-3 supers. A fourth super went onto one colony on the 25th of May and the stack now nearly reaches the shed roof. A four frame nuc has been split off one colony already to cool it down a little. Quite a bit of developing brood has also been harvested at weekly intervals for our research, usually by simply cutting a big slab out of the middle of a frame. This has probably also held the colonies back a bit and it’s only now I’m starting to plan for swarm prevention/control.

Inspections

Inspections have been easier than expected. These colonies are headed by queens with reasonable genetics (Heinz queens – local mongrels of 57 varieties, reared by me in 2015). The bees are steady on the comb and tend not to fly up at you when the crownboard is lifted. They’re nothing particularly special, but would be considered reasonably placid and non-aggressive.

The colony is gently smoked from outside the shed (through the entrance tunnel) and a small amount is wafted under the crownboard or between the QE and the bottom super. After allowing them to settle the supers and crownboard are removed and placed outside on an overturned roof. The queen excluder and adherent bees are also left standing outside (unless it’s cold when the bees are shaken off into the open hive).

Inspecting the colony is straightforward. Any frames removed to make space are rested on the hive stand. Double brooded colonies are split into two, with one box stood aside on an eke on the roof of an adjacent hive roof. Inevitably, the queenless half of the split tends to get tetchy within a few minutes, so it’s best to deal with them first. When frames need to be shaken free of bees this can be done either over the open hive or, better still, directly into a gap between the frames. If done outside many of the nurse bees on the frame fail to get back to the hive (they’ve probably not been on orientation flights yet).

The smoker is usually stood just outside the shed door … if you keep it in the shed during inspections you can end up being kippered 😎

Flying bees

Perhaps surprisingly, even going through all 22 frames in a double colony, the shed does not fill with a maelstrom of flying bees. Undoubtedly this is partly because they’re reasonably calm colonies. Those that do fly rapidly find the window or open door and make their exit. When I first started doing inspections in the bee shed I’d manually help the stragglers outside after reassembling the hive. It turns out that there’s really no need … almost all the bees quickly vacate the shed by making a beeline ( 😉 ) for the bright lights of the windows or doors.

The great escape ...

The great escape …

Just how quickly the bees leave the shed was emphasised last Sunday when selecting larvae for grafting. I opened and inspected a double brooded colony, found a suitable frame with 24 hour larvae on it and placed it in a two frame nuc for protection. Within 5 minutes I could work without a veil (I react very badly to stings to the face so take particular care over this) without interruption from flying bees.

Weather and temperature

I’m sure that the temperature influences the behaviour of the colonies in the shed. They certainly forage – or perhaps collect water to use fondant or crystallised stores – at lower temperatures than those situated outside. When inspections are conducted on a cold day (say 10-11°C) they are even more steady than usual. However, those that do fly take longer to leave the shed and they can end up clustering in small, rather pathetic, little groups which then need to be scooped up on a hive tool and dropped into the colony. On cool days I don’t leave the supers or QE outside the shed as the bees would rapidly get chilled. Work commitments mean that inspections must be conducted on certain days, so I don’t have the luxury of simply waiting until it’s a bit warmer. Although the shed is unheated the temperature differential between the inside and outside is significant – perhaps 4-8°C – or more if the sun is shining on the window side of the shed. On a warm, sunny day the temperature inside the shed can easily reach the mid-20’s which makes inspections a hot and sweaty activity.

Needless to say, inspections on damp or wet days are much better than on colonies located outside. I avoid days when it’s raining hard, partly for my own comfort to avoid getting wet accessing the apiary, but also because I’d prefer not to force the bees to fly on a really wet day. However, on damp or drizzly days, inspections proceed as normal.

And the bad news is …

Almost everything I’ve written above is positive and my overall initial impression is that the bee shed offers very significant advantages for the sort of beekeeping I need to do. However, there are some drawbacks and design issues that either currently cause problems, or might in the future.

The first is that it’s too small. The shed is 12 x 8 feet and I should have got one at least half as long again. This is largely because it’s also used for equipment storage and has a small table for working on. With four hives I need storage for 8-12 supers, additional brood boxes and spare frames. If I was starting again, knowing what I know now, I’d get an 18 x 10 shed with the intention of housing at least 6 colonies and some additional nucs (by contrast mine will accommodate 4 full colonies and 2 nucs down the sunny side of the shed, with the possibility of 2-3 additional nucs at a squeeze). It’s not only equipment storage that takes up the room … you need considerable room to work as well, with space for turning, stacking and temporary placement of hive parts. Working in the bee shed encourages an efficiency of movement – or causes a lot of collisions – I’d not expected.

Essential storage ...

Essential storage …

Secondly the lighting is – at best – variable. On a sunny morning there’s ample light to see eggs and tiny larvae. However, as the colonies have grown, the added supers restrict the amount of light getting through the windows. On an overcast day, or late in the afternoon, the lighting is pretty hopeless – good enough to see queen cups/cells, good enough to locate the queen, but (particularly on dark frames) too dim to see eggs, small larvae or to check frames for signs of disease. It’s not unusual to have to carry frames outside to inspect them fully. I’m currently investigating 12V LED systems run from a solar panel-charged caravan battery. My only concern is that this might disorientate the bees and slow their exit from the shed during inspections.

Multiple supers ...

Multiple supers …

Thirdly, I should have spent more time designing the hive stands. I made them an inch or so too low which caused some problems with locating the hive entrances centrally in the T&G planks, but was not insurmountable. More problematically, as a consequence of the leg locations it’s difficult to keep the floor clear of hive debris that falls through the OMF. With the Varroa boards in place this isn’t an issue, but when they’re out – which I prefer if there’s a chance of the shed getting very warm – the debris needs to be regularly swept up to keep the shed clean. Some sort of removable debris trays would have been a good addition, but are not easy to fit retrospectively. However, the overall hive stand design – with the legs going through the suspended floor to avoid vibrations – works very well.

Finally, swarm control has yet to be tackled. My preferred simple method is doing a vertical split (or using a Snelgrove board that I’m experimenting with this year) but this requires an upper entrance which, obviously, cannot easily be arranged. One possibility is using the Demaree method of swarm control. Alternatively, it would be straightforward to remove the queen into a nuc and let the colony requeen. Currently I’m trying to postpone the inevitable by removal of some brood, ensuring they have enough space within the brood boxes which I swap (top to bottom, bottom to top) periodically, ensuring they have sufficient space in the supers and keeping a close eye on them. The queens are clipped. If they do swarm they’re likely to end up in a lump outside the hive entrance – the ground is flagged and so they should hopefully be relatively easy to scoop up.


 

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

Building frames

Foundationless frames

Foundationless frames …

There’s something repetitively rewarding about building frames for the season ahead. It’s an activity I now tend to associate with early season rather than midwinter, mainly because I have to build them outdoors and it’s simply too cold or wet most winters (a misplaced hammer blow on a really cold fingertip is excruciatingly painful). Since moving to Scotland I don’t have the luxury of a garage/den and the bee shed has no power supply. I could build them indoors, but the incessant nailing/hammering can get a little wearing for other members of the family (as has been made very clear to me). Secondly, it’s the sort of activity that needs a little preparation – both in terms of collecting together the necessary tools, frame parts, nylon, nails, staples, foundation etc and organising them to be close at hand and in the right order during the building process. Good preparation goes a long way to making for a quick and efficient frame building. Finally, it’s repetitive and rewarding – repetitive because I usually set up to make 50-100 at once and rewarding because I get better at it the more I do in any one session. By the time I’m through the first couple of dozen I’m fairly whizzing along, with relatively few nails going awry or frames ending up askew. It’s actually doubly rewarding as the more I do before the season gets into gear the less last-minute panicky frame building will be needed mid-season.

How many?

Assembled frames ...

Assembled frames …

Last weekend I built ~100 brood frames, approximately a 50:50 split between foundationless frames and those with a full sheet of foundation. This, together with about half that number of ‘leftovers’ from last year and some yet-to-be-built super frames for cut comb, should be enough to get me through the season. Remember that although super frames can generally be reused for years it is recommended that brood frames are replaced at least once every three years, usually by rotating out one third of the frames during the season and replacing with fresh ones. With about a dozen hives that means I can expect to use ~40 frames per year for replacements alone. In addition to those I need some for bait hives – for which I almost exclusively use foundationless frames for reasons I’ve previously discussed – together with sufficient frames for the nucs I expect to raise for sale or overwintering. Finally, almost all swarm control procedures (like vertical splits) will require additional frames. Far better there are sufficient in advance of the season than having to scrabble around at the last minute. Been there, done that 😉

Tools of the trade

Tacwise nail gun

Tacwise nail gun …

For a handful – or hive full – of frames a small hammer and gimp pins will do the trick just fine. It’s a beekeeping right of passage to get reasonably competent at this … and also a component of the BBKA ‘Basic’ certificate. However, significantly more than that and you’d be wise to invest in a nail gun. It turns frame building from a somewhat unpleasant, finger-punishing chore into a semi-automatic, smoothly efficient, digitally-undamaging experience. Honestly … your first 50 frames with a nail gun is one of those Archimedian “Eureka” moments that so rarely happens with beekeeping (though a huge prime swarm descending into your carefully-placed bait hive comes close). I’ve discussed foundationless frames at length before so won’t repeat myself here. However, it’s worth noting that an upholsterers staple gun – for example a Tacwise 140EL – together with a few hundred Arrow 8mm stainless steel staples is the easiest way to protect the softwood side bars from the taught monofilament support ‘wires’. These staples withstand the rigours of the steam wax extractor, allowing the frames to be re-used after extraction, though the monofilament stretches and does need replacing.

One nailed and glued ...

One nailed and glued …

For the last year or two I’ve also glued my frames. More specifically I’ve used a dab of waterproof wood glue before using the nail gun to join the side bars to the top bar and to join one of the bottom bars on. The second bottom bar – the one on the same ‘face’ of the frame as the removable fillet in the top bar – isn’t glued in place but is instead simply nailed on with a couple of gimp pins. That way this bottom bar can simply be pried up when taking the frame apart – having extracted the wax using steam – before adding a fresh sheet of foundation.

Kerchunk

Kerchunk …

I do frames in sets of ten, laying out the top bars all orientated the same way (having removed the fillet and dumped them in a ever-growing pile next to me … don’t misplace these as you’ll need them when adding foundation which might happen much later in the season), add a dab of glue to either end where the side bars are attached. I then push side bars onto each, using a swift tap with the hammer to seat them properly, before placing them down top bar down, again all orientated the same way, adding more glue and one of the bottom bars. Since they’re all oriented the same way round there’s no need to check – after the first – which of the two bottom bars is the correct one to add. Then it’s a simple case of kerchunk, kerchunk, kerchunk, kerchunk, kerchunk, kerchunk with the nail gun, a quick eyeball that everything’s straight and true and onto the next frame. Well under ten minutes for ten frames plus a bit of tea drinking time. The ‘wiring’ of foundationless frames (which should be monofilamenting as that’s what I use but it sounds nonsense and isn’t a real word) takes appreciably longer than putting the frames together.

Foundation

still have to attempt to make my own starter strips for foundationless frames. I know how to and I’ve got the wax … what I don’t have is a deep enough heated container to melt the wax in. Until I get round to resolving this I purchase sheets of unwired brood foundation and cut it into 1-1.5 cm strips which are then inserted into the wired frame in the normal manner (after adding the monofilament as previously described).

Thorne's premium ...

Thorne’s premium …

It’s best not to work with foundation if the weather is too cold as it gets very brittle. This year I used up my old stocks of foundation from Kemble or Maisies, and started using a few packets of Thorne’s premium foundation. Irritatingly the latter was a couple of millimetre over-width, meaning that every sheet had to be cut down. Not the end of the world I accept, but nevertheless irritating. The old Maisies or Kemble stuff fitted perfectly. In the photo below it’s the near-white sheets covered with a wax ‘bloom’ … it’s still perfectly usable but just needs to have a hairdryer run over each side to warm it through to restore it to it’s fragrant best.

New and old ...

New and old …

It’s then just a case of finding a suitable place to store all these prepared frames and having a little more patience for the start of the season.

Building bridges

The precarious scaffolding plank bridge that straddles the burn near my apiary got partially washed away during the heavy rainfall and flooding over the last few months. As the bee season is fast approaching and I need to shift some additional equipment and colonies to the apiary, I took advantage of a break in the weather to rebuild the bridge. Or, more accurately, put the planks back in place … ‘build’ makes it sound more than a 20 minute job, which is what it took. It’s a natural crossing point over the burn, as indicated by the roe deer hoof prints (‘slots’) in the soft mud on either side. Whether they’ll risk using the repositioned bridge remains to be seen. Whether it’ll survive discovery by the H+S people also remains to be seen 😉

The apiary occupies a sheltered and sunny corner of open woodland, access is restricted – not least because the bridge is still pretty precarious – and it’s not possible to get a car particularly close to the site. Therefore everything of any size has to be wheeled there on Buster, my (t)rusty hivebarrow. It’s easy to jump across the burn – after all, the deer do it all the time – but I need the bridge for the hivebarrow.

The apiary includes my bee shed, a 12 x 8 foot sturdy shed built onto a solid, level, slabbed foundation. The side of the shed that gets the morning sun has large bee-friendly windows. Inside, there’s a secure set of hive stands that are fixed, not to the shed, but to the underlying slabbed foundation. This ensures that vibrations caused by me wandering around inside the shed aren’t transmitted to the bees by the continued flexing of the floor. If you jump and land heavily on both feet in the shed the bees give a small roar of recognition/agitation. However, since I don’t normally pogo around my hives this isn’t an issue … during normal bumbling around the colonies they’re silent.

Feet through the floor ...

Feet through the floor …

I’m new to bee sheds, so am still learning … time will tell whether the modifications I’ve made to help house the hives – largely suggested by generous contributors to the SBAi, gleaned from the internet or simply guessed at – are suitable. For example, the hive floors are currently bolted onto the hive stands to avoid my inevitable engulfment in escaped bees if one were to get bumped inadvertently. In some bee sheds I’ve read the hive entrances are simply lined up with a hole in the shed wall. However, for a variety of reasons I and others want to be able to work in the shed without beesuits, so I have entrance tunnels that connect the floor to the shed wall.

Winter colony activity

Winter colony activity …

There are currently two colonies in situ. Both appear to be doing fine. Despite the temperature being appreciably warmer inside the shed (it’s unheated, but quickly warms once the sun is on it) they don’t fly if the outside temperature is too cold. On very cold days the colonies are tightly clustered. However, there are days when bees outside are clustered very tightly, but those inside are in a far looser mass. There’s also more evidence of activity within the colony – in terms of stores being uncapped and brood rearing. This isn’t to say that all similarly housed colonies would behave the same … the differences I see in the small number of colonies I’ve looked at might simply be due to genetic differences between the bees. Examination of the Correx Varroa boards shows the expected ‘stripes’ of wax granules from brood rearing and you can even see a few eggs that have been discarded and dropped through the OMF. The Varroa counts are very low. These colonies were treated by vaporisation about 8 weeks ago and have only dropped a couple of mites since then. However, I appreciate that mite drop counts are notoriously unreliable, but at least there aren’t hundreds 😉

Insulation ...

Insulation …

Several of my colonies had still not finished with their fondant blocks by late into November. These blocks had been housed over a queen excluder in an empty super, underneath the usual insulated perspex crownboard. To avoid a dead space above the colony I filled the super with some of that ‘inflated’ sealed plastic bag wrapping often supplied with packages from Amazon or similar mail-order suppliers. Bubblewrap can be used in the same way.

Far better this stuff is used than just dumped into a landfill …

Waiting ...

Waiting …

 

Waving not drowning

Marooned ...

Marooned …

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 …

Snowdrops

Snowdrops

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 ...

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.

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 ...

Yet more snowdrops …


The title of this post is a play on the title of a poem by Stevie SmithNot 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 to treat?

Preparing Apiguard

Preparing Apiguard …

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 vaporiser etc. 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

DWV symptoms

DWV symptoms

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

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 ...

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?

The apiary in winter ...

The apiary in winter …

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.

In conclusion

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

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

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.


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 …

References

Overwintering honey bees: biology and management from the Grozinger lab.

Managing Varroa (PDF) by the National Bee Unit