Category Archives: Seasonal

2019 in retrospect

The winter solstice, the shortest day of the year, is tomorrow. It will be a long time until there’s any active beekeeping, but at least the days are getting longer again 🙂 

The queens in your colonies will soon – or may already – be laying again.

What better time to look back over the past season? How did the bees do? How did you do as a beekeeper? What could be done better next time?

Were there any catastrophic errors that really must not be repeated?

Overview of the season

Overall, in my part of Scotland, it was about average.

But that, of course, obscures all sorts of detail.

Spring was warm and swarming started early. I hived my first swarm before the end of April and my last in early July. This is about twice the length of the usual swarming season I’ve come to expect in Scotland. However, it wasn’t all frantic swarm management as there was a prolonged ‘June gap’ during which colonies were much more subdued.

The summer nectar, particularly the lime, was helped by some rain, but the season was effectively over by mid-August. I don’t take my colonies to the heather. Overall, the honey crop was 50-60% that of the (exceptional) 2018 season.

Looking at the yields from different apiaries for spring and summer it’s clear that – despite the warm spring – colonies did less well on the early season nectar (~40% that of 2018). I suspect this is due to their being less oil seed rape (OSR) grown within range of my apiaries. The colonies were strong, but the OSR just wasn’t close enough to be fully exploited..

Over recent years the area of OSR grown has reduced, a trend that is likely to continue.

Winter oil seed rape – the potential is not obvious

The winter rape is already sitting soggily in the fields; I’ve chatted to a couple of the local farmers and will move some hives onto these fields if colonies are strong enough and the weather looks promising.

Bait hives

Every year I’ve been back in Scotland I’ve put a bait hive in the garden.

Every year it has attracted a swarm.

This year – with the extended swarming season – it led to the capture of three swarms in about 10 days. As the June gap ended the weather got quite hot and sultry 1 and the first swarm arrived near the end of that month.

One week after the first swarm arrived there was lots more scout bee activity. There were also quite a few dead or dying bees littering the ground underneath the bait hive. It turned out that these were the walking wounded (or worse) scout bees from two different hives fighting.

Gone but not forgotten

Within 48 hours another swarm arrived and I was fortunate enough to watch it descend.

Incoming!

I moved the hive that evening, placing another bait hive on the same spot. By the following morning there were yet more scout bees checking the entrance and a third swarm – by far the biggest of the three – arrived later that day.

Each was a prime swarm and none were from my own hives which are in the only apiary 2 within a mile of the bait hive.

Watching the scout bees check out a bait hive is always interesting. There’s a fuller account of the observations and lessons learnt – of which there were several – written in the post titled BOGOF (buy one get one free 😉 ).

Swarm prevention

My swarm prevention this year either used the nucleus method or vertical splits (with an occasional Demaree for good measure) for most hives. All prevented the loss of swarms and queen mating went about as well – or badly – as it usually does i.e. never as fast as I’d like, but (eventually) all were successful.

Split board

Split board …

I did miss a couple of swarms. One relocated underneath the OMF of the hive it originated from because the queen was clipped and, having fallen ignominiously to the ground, she just clambered up the hive stand again.

The second swarm was also not lost as I inadvertently trapped the queen on the wrong side of the queen excluder. D’oh! In my defence, I’ve had a rather busy year at work 3 and it’s little short of a miracle that I got any beekeeping – let alone swarm control – done at all.

Mites

Considering the extended June gap, which resulted in a brood break for some colonies, mite levels were appreciably higher this year than last. I think this can largely be attributed to the warm Spring which allowed colonies to build up fast. Several colonies were strong enough to swarm in late April.

I do a limited amount of mite counting during the season but also monitor virus loads in emerging bees in our research colonies. In most colonies these stayed resolutely low and no production colonies needed any mid-season interventions for mite control.

Poly Varroa tray from Thorne's Everynuc with visible mites.

Gotcha! …

Newly-arrived swarms were treated as were some broodless splits. The former because many swarms carry a larger than expected mite population 4 and the latter because it’s an ideal opportunity to target mites as – in the absence of brood – all will be phoretic.

All colonies were treated with Apivar immediately after the summer honey came off. At the same time they were fed copious amount of fondant in preparation for the winter ahead.

In late November most colonies were broodless and were treated with a vaporised OA-containing miticide.

What worked well

In what was a pretty tough year for non-beekeeping reasons even small beekeeping successes have assumed a significance out of all proportion to the effort expended on them.

In my first year or two of beekeeping honey extraction was an unbridled pleasure. As hive numbers increased it because more of a chore. An electric extractor marginally improved things.

However, there was still the never-ending juggling of frames trying to balance the extractor and jiggling of the unbalanced machine as it sashayed across the floor.

Rubber-wheeled castor with brake

Two years ago I purchased some rubber braked wheels to add to the extractor legs.

This year I finally got round to fitting them.

The jiggle-free revolutions were a revelation 🙂

I know some beekeepers who stand their extractors on foam pads. Others who have them bolted to a triangular wooden platform. I can’t imagine either solution works better than these castors, which also make moving the extractor to and from storage much easier.

I changed my hive numbering system this season. I’d previously referred to hives by position or with a number written on the box. This caused some issues with the (sometimes shambolic) way I do my beekeeping.

If the hive moves and it’s numbered by position then its number should change. Manageable, but a bit of a pain.

If the position does not change but they’re expanded from a nuc to a full brood box do they get a new number or retain the old one? A problem if it’s written on the box.

And what happens when you move queens about in the apiary (which we sometimes need to do for work)?

Numbers for hives and queens

Numbers for hives and queens

All hives and queens were assigned a number – small red discs for the queen and big, bold numbers for the box. They stay with the colony or the queen … and the records 😉

This has worked very well. As colonies expand the numbers move, if queens are moved I know from and to where (and keep a separate record of queen performance). When colonies are united the queenless component loses both the queen number and the colony number.

The numbering has been a great success. The numbers themselves less so. Most of the red discs have faded very badly and a few of the hive numbers have cracked and/or blown away.

Numbered nuc and production colonies.

Never mind … the system works as intended and it has significantly improved my record keeping. I now know which hive and queen I’m referring to 😉

The Apiarist in 2019

I might squeeze in a more thorough overview of funny search terms and page accesses before the New Year. Briefly … there are significantly more subscribers and an increase of ~20% in overall page reads.

This year marks the sixth full season of The Apiarist which still surprises me. There still seem to be things to write about. Post length continues to increase, though the overall number of posts remain almost exactly one a week. Amazingly I’ve written nearly 95,000 words this year.

Words, words, words …

We had some server issues but most of these appear to have been resolved. Spam remains a problem and the machine auto-filters several hundred messages a day to keep my inbox only unmanageably overflowing. It has meant I’ve had to add some “I am not a robot” CAPTCHA trickery to the contact and/or comment forms. I’m aware that this has caused some problems making contact but can’t find an alternative solution that doesn’t swamp me in adverts for fake sunglasses, Bitcoins or Russian brides.

I live in Scotland and have no use for any of these things 😉 5

The year ahead

There are three main items on the ‘to do’ list for 2020 6.

The first is to start queen rearing again. Pressure of work has prevented this from happening over the last couple of seasons and I’m missing both the huge satisfaction it brings and the improved control over stock improvement. I’ve done lots of queen rearing in the past, but work has muscled its way in to too many weekends and evenings recently 7.

3 day old QCs ...

3 day old QCs …

I now have some perfectly adequate bees.

Actually, although they’re far from ‘perfect’ they are also far better than ‘adequate’.

I’ve got a couple of lines that have too much chalkbrood and almost all of them are less stable on the comb than I’d like. They don’t fall in wriggling gloops off the corner of the frame as some do, but they’re more active than I’d prefer. It’s a trait that has crept into some stocks over the last couple of years and I need to try and get rid of it.

The second is to provide better information on the provenance of my honey to potential and actual purchasers. There’s increasing interest in sourcing high quality local food and, as I’ve discussed recently on honey pricing, we should be aiming to provide a premium product (at a premium price 😉 ). The public are also increasingly aware that some of the major supermarkets have been reported to be selling adulterated honey. Providing details of the batch, the apiary and the area in which it was produced should help define it as a quality local product.

And generate repeat business.

Local honey

Finally, I’m planting up a new apiary on the west coast with dozens of pollen-bearing trees before I start beekeeping there. This has been a long and protracted process as it has involved clearing large areas of invasive rhododendron. The first 125+ native trees go in this winter – a mix of alder, loads of willow, hazel, blackthorn and wild cherry. More will follow if I manage to stop the deer eating them all.

Only another few acres of rhododendron to clear 🙁

The new apiary is in a Varroa-free region so I will not be moving my current bees there, but instead sourcing them from other areas fortunate enough to be mite-free. This is a long-term project.

Bee shed #3 … bigger and better.

The trees will need a few years to mature but the bee shed (bigger than all that have gone before 🙂 ) foundations are finished and the shed will be assembled sometime in March.

Holibobs

The holiday period is almost here. Many beekeepers will be thinking about fondant top-ups and oxalic acid mite treatment. I’ve done the latter already and – if your colonies are also broodless – hope you’ve done the same. All my hives remain reassuringly heavy but as the weather warms and brood rearing gears up I’ll have some fondant ready ‘just in case’.

I’ve covered last-minute beekeeping gifts in previous years. I think the (digital edition) American Bee Journal remains good value and provides a different perspective for UK beekeepers of what happens in the US.

And with that I’ll pour another glass of mead red wine 8 and wish you all Happy Christmas/Holidays (delete as appropriate).

David


 

Rinse and repeat

Midwinter mite treatment is no substitute for a properly applied late summer treatment that protects your all important winter bees. However, you also need to control mites in the winter or there is a good chance their numbers will reach damaging levels the following season 1.

Mid September

Late summer treatment and no winter treatment – mite levels in red.

OA (oxalic acid-containing) treatments are the ones to use in midwinter (e.g. Api-Bioxal). These can be trickled in syrup onto each seam of bees or they can be vaporised (sublimated), effectively coating everything in the hive with a very fine dusting of crystals.

Trickling damages open brood whereas sublimation is exceedingly well-tolerated by the colony.

If you are certain the colony is broodless then trickling is faster 2 and – because you don’t need power or any more PPE 3 than a pair of gloves – much easier.

If the ambient temperature is consistently below ~6°C and I know the colony is broodless I usually trickle. If the temperature is higher and/or I’m uncertain about whether there is brood present I usually vaporise.

I watch the weather and treat after the first prolonged cold spell of the winter.

Experience over the last few years suggests this is when colonies are most likely to be broodless.

Most likely is not the same as certain 🙁

Count the corpses

After treating I closely monitor the mite drop over several days. I use white Correx Varroa trays that slide underneath the open mesh of my kewl floors.

Easy counting ...

Easy counting …

I don’t count the mites every day, but I do try and count the day after treatment and 2-4 days later. I record the mite drop per hive and, over time, look for two things:

  1. The cumulative mite drop. This indicates the original infestation level of the hive. Usually it’s in the range 10-75 mites (total) for my colonies in midwinter, but – as you’ll see – it can be much higher.
  2. The speed with which the daily mite drop falls to a low single-digit average. OA treatment is very effective at killing phoretic mites. If there’s a continuing high level of mite drop it suggests that more are getting exposed over time.

In my experience, vaporised OA often results in a greater mite drop 24-48 hours post-treatment rather than in the first 24 hours 4. After that I expect (hope) the daily mite drop tails off very quickly.

Vaporised OA remains effective in the hive for several days. Randy Oliver reports studies by Radetzki who claims it remains effective for up to three weeks. I think this is an overestimate but I’m sure it continues working well for four to five days.

OA, whether vaporised or trickled, on broodless colonies is 90-95% effective i.e. if there were 100 mites in the colony you should expect as few as 5 remain after treatment.

Four to five days after the initial treatment I eyeball the numbers across all the hives in an apiary and look at the profile of the mite drop.

Mite drop profiles

I couldn’t think of a better term for this. Essentially, it’s the shape of a graph of mites dropped per day after treatment.

I don’t usually draw the graph – I have a life – but I do look carefully at the numbers.

Here are a couple of sketched graphs showing what I mean. Days are on the horizontal (X) axis, dead mites per day are on the vertical (Y) axis. Treatment applied on day 0. No count (yet) on day 6.

Mite drop profile – this is what you want

In the graph above there are high(er) levels of dropped mites on the first day or two after treatment, but levels thereafter drop to a basal level of perhaps 1-4 mites per day.

Each time I count the mites I clean the Varroa tray (the rinse in the title of the post).

Assuming the day 5 mite drop is very low, the profile above is what I’m looking for. It shows that treatment has worked and no repeat is necessary.

The profile below is much less promising 5.

Mite drop profile – this suggests additional treatment is needed

In this graph (above) the mite drop remains high every day after treatment. Sometimes they even increase over time.

If you assume treatment is equally effective – say 90%+ – on the five days after treatment 6 this must mean that there are mites being killed on days 4 and 5 that were not exposed to treatment on the earlier days.

How can this be?

The most likely explanation is that the colony had some sealed brood that has emerged in the days following treatment, exposing previously ‘hidden’ mites to the miticide.

It’s good that they’ve perished, but are there more hiding? How do you tell?

Enough of my hand drawn idealised graphs with no real numbers … what about some actual data?

Real world data

The graph below shows data for seven colonies in a single apiary. All were treated with Apivar in late summer. All were treated with a vaporised oxalic acid-containing treatment on the 28th of November. 

Mite drop profiles – real world data

I counted the mite drops on the 29th (T+1), the 2nd (T+4) and 3rd (T+5). The figures for 30th to the 2nd were averaged, which is why the bars are all the same height.

  • Colonies 3 and 6 had very low mite levels. Though not the lowest in the apiary 🙂
  • Colonies 2 and 7 had pretty good mite drop profiles, with low single-digit numbers on day T+5. None of these four colonies (2, 3, 6, 7) need treating again.
  • Colonies 1 and 5 have high mite levels 7 and – despite the pretty good levels on T+5 in colony 1 – were both re-treated.
  • Colony 4 was also treated again as the profile was flat and I suspected they had low levels of mites but were rearing brood..

And repeat

Note: The instructions for Api-Bioxal specifically state that the maximal dose of 2.3g/hive should be made in a single administrations with only one treatment per yearPrior to the VMD licensing and approval of Api-Bioxal there was effectively tacit approval for beekeepers to use unadulterated oxalic acid by trickling or vaporisation, without any particular limitations on frequency of usage.

It’s worth stressing that you should not repeat oxalic acid trickling 8.

Here is some real data for repeat treatments of another colony in the same apiary.

Repeat treatment for brood-rearing colony

The average mite drop per day over the first 5 days was ~60. This justified an additional treatment. Over the next 6 days 9 the average drop was ~20. I considered a third application was needed after which the mite drop per day was in the low single digits.

And again

Repeated treatment is needed if there is sealed brood in the colony.

The likelihood is that two additional treatments will be required.

Why two?

Here’s a reminder of the development cycle of the Varroa mite in developing worker or drone brood.

Repeated oxalic acid vaporisation treatment regime.

Worker brood occupies capped cells for 12 days (days 10 – 21 of development, shown above). Vaporised oxalic acid-containing treatments show a drop in efficacy after 4-5 days 10.

Therefore, to cover a complete cycle of capped brood, you need 3 x 5 day treatments to be sure no mites emerge without them being greeted with a lethal dose of something really, really unpleasant 😉

There should be no drone brood in your winter hives 11 but, if there was, 3 x 5 day treatments should just be enough to cover the complete cycle of capped drone brood as well. However, a fourth treatment might be needed.

Note (again): The instructions for Api-Bioxal specifically state that the maximal dose of 2.3g/hive should be made in a single administrations with only one treatment per year

Not all hives are equal

There are 15 hives in the apiary containing the bee shed. Colony 1 had just about the highest mite levels. However, as shown in one of the graphs above, adjacent colonies can have markedly different mite levels.

There is no clear correlation between mite drop after treatment and colony size. Colony 1 is a double brood monster, but the others in the bee shed are all single brood 10 and 11 frame Nationals 12.

Some colonies need repeated treatment, others did not.

To maximise efficient treatment and minimise unnecessary miticide usage it is necessary to monitor all the colonies.

It’s also worth noting that monitoring only a single hive in an apiary may be misleading; compare colonies 1 and 6 above in the graph of real data from the bee shed.

This monitoring takes just a few minutes. I usually do it after work. In the bee shed this is easy as I now have LED lighting and it’s nice and dry.

Easy conditions to count mites

In my out apiaries I have to do it by headtorch … under an umbrella if it’s raining 🙁

Checking mite drop by torchlight

That’s the last job of the winter completed … time now to review the season just gone and plan for next year.


Colophon

Rinse and repeat

Rinse and repeat is a truncation of instructions often found on the side of shampoo bottles – Lather, rinse and repeat. Other than potentially resulting in an endless loop of hair washing, it also means that a process is (or needs to be) repeated.

In The Plagiarist by Benjamin Cheever, a marketing executive becomes an industry legend by adding one word – REPEAT – to shampoo bottles. He doubles sales overnight.

For Varroa treatment the instructions should be amended to Repeat if necessary … and note again the instructions on Api-Bioxal which, at the time of writing, is the only oxalic-acid containing VMD approved miticide that can be administered by vaporisation.

 

Midwinter, no; mites, yes

There’s a certain irony that the more conscientious you are in protecting your winter bees from the ravages of Varroa in late summer, the more necessary it is to apply a miticide in the winter.

Winter bees are the ones that are in your hives now 1.

They have a very different physiology to the midsummer foragers that fill your supers with nectar. Winter bees have low levels of juvenile hormone and high levels of vitellogenin. They are long-lived – up to 8 months – and they form an efficient thermoregulating cluster when the external temperature plummets.

Winter bees production

In the temperate northern hemisphere, winter bees are reared from late summer/early autumn onwards. The combination of reductions in the photoperiod (day length), temperature and forage availability triggers changes in brood and forager pheromones.

Factors that influence winter bee production

Together these induce the production of winter bees.

For more details see Overwintering honey bees: biology and management by Döke et al., (2010).

Day length reduces predictably as summer changes to autumn. In contrast, temperature and forage availability (which itself is influenced by temperature and rainfall … and day length) are much more variable (so less predictable).

All of which means that you cannot be sure when the winter bees are produced.

If there’s an “Indian summer“, with warm temperatures stretching into late October, the bees will be out working the ivy and rearing good amounts of brood late into the year. The busy foragers and high(er) levels of brood pheromone will then delay the production of winter bees.

Conversely, low temperatures and early frosts reduce foraging and brood production, so bringing forward winter bee production.

It’s an inexact science.

You cannot be sure when the winter bees will be produced, but you can be sure that they will be reared.

Protect your winter bees

And if they are being reared, you must protect them from Varroa and the viral payload it delivers to developing pupae. Most important of these viruses is deformed wing virus (DWV).

Worker bee with DWV symptoms

Worker bee with DWV symptoms

Aside from “doing what it says on the tin” i.e. causing wing deformities and other developmental defects in some brood, DWV also reduces the longevity of winter bees.

And that’s a problem.

If they die sooner than they should they cannot help in thermoregulating the winter cluster.

And that results in the cluster having to work harder to keep warm as it gets smaller … and smaller … and smaller …

Until it’s so small it cannot reach its food reserves (isolation starvation) or freezes to death 2.

So, to protect your winter bees, you need to treat with an appropriate miticide in late summer. This reduces the mite load in the hive by up to 95% and so gives the winter bees a very good chance of leading a long and happy life 😉

Time of treatment and mite numbers

Time of treatment and mite numbers

I discussed this in excruciating detail in 2016 in a post titled When to treat?.

The figure above was taken from that post and is described more fully there. The arrow indicates when winter bees are produced and the variously coloured solid lines indicate mite numbers when treated in mid-July to mid-November.

The earlier you treat (indicated by the sudden drop in the mite count) the lower the peak mite numbers when the winter bees are being reared.

Note that the mite numbers indicated on the right hand vertical axis are not ‘real’ figures. They depend on the number present at the start of the year. In the figure above I “primed” the in silico modelled colony with just 20 mites. This will become very important in a few paragraphs.

Late season brood rearing

Compare the blue line (mid-August treatment) with the cyan line 3 (mid-October treatment) in the figure above.

The mid-October treatment really hammers the mite number down and they remain low until the end of the year 4.

The reason the mite numbers remain low after a mid-October treatment is that there is little or no brood being reared in the colony during this period.

Mites need brood, and specifically sealed brood, to reproduce on.

In the absence of brood the mites ‘colony surf‘, riding around as phoretic mites on nurse bees (or any bees if there aren’t the nurse bees they prefer).

And that late season brood rearing is the reason the end-of-year mite number for the colony treated in mid-August (the blue line) remains significantly higher.

Mites that survive the miticide in August simply carry on with their sordid little destructive lives, infesting the ample brood available (which could even include some highly mite-attractive and productive drone brood) and reproducing busily.

So, the earlier you treat, the more mites remain in the hive at the end of the year.

Weird, but true.

Early season brood rearing

The winter bees don’t ‘just’ get the colony through the winter.

As the day length increases and the temperature rises the colony starts rearing brood again. Depending upon your latitude it might never stop, but the rate at which it rears brood certainly increases in early spring.

Or, more correctly, in mid- to late-winter.

And it’s the winter bees that do this brood rearing. As Grozinger and colleagues state Once brood rearing re-initiates in late winter/early spring, the division of labor resumes among overwintered worker bees.”

Some winter bees revert to nurse bee activity, to rear the next generation of bees.

And this is another reason why strong colonies overwinter better … not because they (also) survive the cold better 5, but because there are more bees available to take on these brood rearing activities.

Strong, healthy colonies build up better in early spring.

Colonies that are weak in spring and stagger through the first few months of the year, never getting close to swarming, are of little use for honey production, more likely to get robbed out and may not build up enough for the following winter.

Midwinter mite treatments

Which brings us back to the need for miticide treatment in midwinter.

The BEEHAVE modelled colony shown in the graph above was ‘primed’ at the beginning of the season with 20 mites. These reproduced and generated almost 800 mites over the next 10-11 months.

What do you think would happen if you start the year with 200 mites, rather than 20?

Like the 200 remaining at the year end when you treat in mid-August?

Lots of mites … probably approaching 8000 … that’s almost as many mites as bees by the end of the season.

So, one reason to treat in the middle of winter is to reduce mite levels later in the season. The smaller the number you start with, the less you have later.

Vapour leaks out ...

Vaporisation … oxalic acid vapour leaks out …

But at the beginning of the season these elevated levels of mites could cause problems. High levels of mites and low levels of brood is not a good mix.

There’s the potential for those tiny patches of brood to become mite-infested very early in the season … this helps the mites but hinders the bees.

Logically, the more mites present at the start of brood rearing, the more likely it is that colony build up will be retarded.

So that’s two reasons to treat with miticides – usually an oxalic-acid containing treatment – in midwinter.

Midwinter? Or earlier?

When does the colony start brood rearing again in earnest?

This is important as the ‘midwinter’ treatment should be timed for a period before this when the colony is broodless. This is to ensure that all the mites are phoretic and ‘easy to reach’ with a well-timed dribble of Api-Bioxal.

In studies over 30 years ago Seeley and Visscher demonstrated that colonies have to start brood rearing in midwinter to build up enough to have the opportunity to swarm in late spring. These were colonies in cold climates, but the conditions – and season length – aren’t dramatically different to much of the UK.

Low temperatures regularly extend into January or February. The temperature is also variable year on year. It therefore seems (to me) that the most likely trigger for new brood rearing is increasing day length 6.

The apiary in winter ...

The apiary in winter …

I therefore assume that colonies may well be rearing brood very soon after the winter solstice.

I’m also aware that my colonies are almost always broodless earlier in the winter … or even what is still technically late autumn.

This is from experience of both direct (opening hives) or indirect (fresh brood mappings on the Varroa tray) observation.

Hence the “Midwinter, no” title of this post.

Don’t delay

I therefore treat with a dribbled or vaporised oxalic acid-containing miticide in late November or early December. In 2016 and 2017 it was the first week in December. Last year it was a week  later because we had heavy snow.

This year it was today … the 28th of November. With another apiary destined for treatment this weekend.

If colonies are broodless there is nothing to be gained by delaying treatment until later in the winter.

Most beekeepers treat between Christmas and New Year. It’s convenient. They’re probably on holiday and it is a good excuse to escape the family/mince pies/rubbish on the TV (delete as appropriate).

But it might be too late … don’t delay.

If colonies are broodless treat them now.

If you don’t and they start rearing brood the mites will hide away and be unreachable … but their daughters and granddaughters will cause you and your bees problems later in the season.

Finally, it’s worth noting that there’s no need to coordinate winter treatments. The bees aren’t flying and the possibility of mites being transferred – through robbing or drifting – from treated to untreated colonies is minimal.


 

Strong hives = live hives

Science and beekeeping make for interesting contrasts and can be awkward bedfellows 1.

Science is based upon observation of tested single variables. multiple repeats and statistical analysis. It builds on what has gone before but has accepted processes to challenge well-established theories. Some of the greatest advances are made by young researchers willing to test – and subsequently overturn – established dogma.

Over the last three generations science – both how we do it and what we understand – has changed almost beyond recognition.

In contrast, beekeeping is steeped in history, has multiple variables – climate, forage, ability – and very small sample sizes. It tends to be taught by the most experienced, passing down established – though often not rigorously tested 🙁 – methods 2.

As a consequence our beekeeping has barely changed over the last three decades. Established dogma tends to stay established.

Local bees are better adapted to local conditions

So let’s look in a little more detail at one of these established ‘facts’ … that locally reared bees are better adapted to local conditions.

The suggestion here is that locally reared bees, because they’re ‘better adapted’ (whatever that means) are more likely to flourish when the going is good, and more likely to survive when the going gets tough.

Furthermore, the implication is that they’re more likely to do better in that environment than bees reared elsewhere (and that are therefore adapted to a different environment).

This sounds like common sense.

Locally bred queen ...

Locally bred queen …

As Brexit looms and the never-ending supply of early-season Greek or Slovenian queens disappears perhaps it’s also fortunate, rather than just being common sense.

But, as a scientist, I’ve spent a career questioning things.

Every time I read the “locally adapted bees survive better (or perform better, or whatever better)” 3 two questions pop into my head …

  1. What’s local?
  2. How did they prove – or how would I test – this?

Spoiler alert

There is evidence that local bees show adaptive changes to their local environment. There is also evidence that local bees do better in their local environment.

Formally, I don’t think scientists have demonstrated that the former explains the latter. This might seem trivial, but it does mean that our understanding is still incomplete.

However, I’m not going to discuss any of these things today – but I will in the future.

Instead I’m going to deal with those two questions that pop into my head.

If we tackle those I think we’ll be better placed to address that dogmatic statement that local bees are better adapted to local conditions in due course.

But perhaps we’ll first discover that other things are more important?

What’s local?

I live most of the time in central Fife. It’s a reasonably dry, relatively cool, largely arable part of the UK with a beekeeping season that lasts about 5 months (from first to last inspections).

Are my (fabulous 😉 ) locally bred queens adapted for central Fife, or the east of Scotland, or perhaps north-west maritime Europe, or Europe?

Where have all my young girls gone?

What a beauty

Would these locally adapted bees do better here (in Fife) than bees raised in the foothills of the Cairngorms, or the Midlands, or Devon or East Anglia … or Portugal?

If you measure the environment you’ll find there’s significant overlap in terms of the climate, the temperature, the forage, the day length (or a hundred other determinants) with other regions of the UK.

The temperature or rainfall extremes we experience in central Fife aren’t significantly different to those in the Midlands. The season duration is different (because of latitude), but I had lots of short seasons in the Midlands due to cool springs and early autumns.

Local is an ill-defined and subjective term.

But there are differences of course. Are Ardnamurchan bees better able to cope with the rain (and the fantastic scenery) than Fife bees? Are Fife bees better able to exploit arable crops than those foraging on the heather and Atlantic rainforests that cloak the hills in the far west of Scotland?

I don’t know 🙁

And there’s something else I don’t know

I also don’t know how I would meaningfully test this.

Just thinking about these types of experiments makes me nervous. Think of the year to year variation – in weather, forage etc. – compounded by the hive to hive variation.

Then multiply that by the variation between beekeepers.

This last one is a biggy. Two beekeepers of differing abilities will experience very different levels of success – quantified in terms of honey yield or hives that survive for example – in the same season and environment.

Doing a study large enough to be statistically relevant without having such enormous variation that the results are essentially meaningless is tricky.

What a nightmare.

Which, in a roundabout way, brings me to a paper earlier this year by Maryann Frazier and Christina Grozinger from Penn State University.

Ask the question in a different way

The title of the paper tells you most of what you need to know about the study.

Colony size, rather than geographic origin of stocks, predicts overwintering success in honey bees (Hymenoptera: Apidae) in the northeastern United States. 4

But don’t stop reading … let’s look in a bit more detail at what they did.

They approached the question (that local bees are better adapted) from a slightly different angle.

Essentially the question they asked was “Does the geographic origin of the bees influence the overwintering survival of bees in a temperate region?”

This question is easier to answer.

They defined the parameters of the experiment a bit more clearly. For example:

  • Rather than looking at several regions they just studied bees in one area  – Pennsylvania (the temperate region in the title of the paper).
  • The bees came from four sources; two were from a hot geographic region of the USA and two from a cold region.
  • They scored ‘doing better’ only in terms of overwintering survival.

By simplifying the question they could reduce some of the variables. They could therefore increase the quantification of the parameters (colony weight, strength/size etc.) that might influence the ‘doing better’.

And in doing so, they came up with an answer.

The study

Sixty colonies were established in three apiaries in Pennsylvania. Two of the apiaries (A & B) were within 1 mile of each other, with the third (C) about 15 miles away. Colonies were generally established from packages 5, to which a queen was introduced from one of four different queen breeders.

Two of the queen breeders were from southern USA (Texas or Florida) and two from northern USA (Vermont and West Virginia 6.

The authors used microsatellite analysis to confirm that the queens – after introduction – headed genetically distinct colonies by midsummer 7.

So far, so good …

They then used standard beekeeping methods to manage the colonies – regular inspections, Varroa treatments as appropriate, feeding them up for winter etc.

They scored colonies for a variety of ‘parameters’; net weight, frames of brood, adult bees and stores.

Four queens failed before winter.

And then they overwintered the remaining 56 colonies …

The results

… of which only 39 survived until April 🙁

39/56 sounds a pretty catastrophic loss to me but it’s actually about the same (~30%) as the average winter losses reported each year in the USA.

So, did the ‘cold-adapted’ 8 Vermont queens survive and prosper? Did the ‘Southern Belles’ 9 from Texas all perish in the cold Pennsylvanian winter?

No.

That’s no to both questions.

There was no significant difference in survival of colonies headed by queens from the north or the south.

The geographic ‘origin’ of the bees did not determine colony survival.

They may have been ‘locally adapted’ (to Vermont, or Texas or wherever) and they were certainly genetically distinct, but it made no difference to whether the colony perished or not in Pennsylvania.

So if the source of the queen didn’t influence things, what did?

Weighty matters

This is the key figure from the paper.

Overwintering success is significantly associated with colony weight.

The heavier a colony was in October, the more likely that the colony survived until April.

The left hand panel shows the probability of a colony surviving (vertical axis, solid line) plotted against the net weight of the colony.

Below about 30 kg colony survival dropped significantly.

The right hand panel shows that net weight alone was not the only determinant. This plots colonies ranked by weight (vertical axis) and indicates whether they survived or not. An underweight (i.e. under 30 kg) colony in apiary C was much more likely to survive than a similar weight colony from the other two apiaries.

Allee, Allee 10

The heavier the colony, the greater the chance it survived. Furthermore, it wasn’t simply the amount of stores available.

Heavier colonies were also larger colonies.

This indicates a so-called Allee effect 11 which is a positive correlation between population density and individual fitness.

This has been shown before for honey bees (and other social insects). For bees we know that the larger the winter cluster the better they are able to maintain the correct overwintering temperature. These large clusters show lower per capita honey consumption to maintain the same temperature when compared to small clusters.

However, in addition to not running out of stores (due to more frugal usage) 12, large colonies will also be better able to rear brood in early spring … ‘it takes bees to make bees’.

Taken together these results demonstrate that colony size and weight, rather than geographic adaptation, is probably the most important determinant of overwintering colony survival.

Disease interlude

These studies were conducted in 2013 (and published in 2019 … a feature of some of my science 🙁 ). In the previous year the authors set up a similar study but did not manage Varroa levels.

Under these conditions only 12% of the colonies survived.

There’s a lesson there I think 😉

This disastrous 2012 study used the same queen breeders to source their queens (from Texas, Florida, West Virgina and Vermont). Some of these queens were described and sold as ‘Varroa-resistant’.

There was no difference in survival (or, more accurately, death) rates between colonies headed by queens described as ‘Varroa-resistant’ or not.

Another lesson perhaps?

Is there a geographic component to Varroa-resistance? Are Varroa-resistant Vermont colonies only actually resistant to mites from Vermont?

Or their viruses? 13

OK, we’re getting distracted … let’s return to apiary C.

Forage diversity and abundance is also important

Colonies in apiary C survived better at lower overall net weights than colonies from other apiaries. In addition, average colony weights were higher in apiary C than in the other two apiaries.

Apiary location significantly affected colony weight and survival.

And the abundance and range of nectar sources was significantly different between the three apiaries used in this study, with colonies from apiary C – located in a less forested and more agricultural area – surviving better.

The proportion of land cover/land use types surrounding apiaries.

The authors suggest that the forage diversity and abundance around apiary C increased the size of the colonies (by boosting brood rearing, adult longevity and colony growth) and that it was this larger adult population, rather than colony weight per se, that was important.

Are we getting the message?

This is the second time in a month that I’ve discussed the importance of strong colonies.

A few weeks ago I discussed how strong colonies are more profitable because they generate a surplus of honey or bees, both of which are valuable.

In this post I show that the primary determinant of overwintering success is the strength and weight of the colony. The source of the queen – whether from the balmy south or the frosty north – had no significant influence on colony survival.

This doesn’t mean local bees aren’t better adapted to local conditions. That wasn’t what was being tested.

However, it does suggest that other things that may be as important, or perhaps more important.

The take home message from this study is keep strong colonies in a forage-rich environment.

In a future post I’ll discuss the evidence that local bees are better adapted … and I’ll make the suggestion that some of these adaptations might be explained because the local genotype actually produces stronger colonies 😉


Note

This was originally published with the title Correlates of winter survival on 8/11/2019 but a hamster running amok in the server meant that the email to those registered to receive announcements of new posts was never sent. Rather than let the post disappear into digital oblivion – as the take home message is an important one – I’m re-posting it again.

With apologies to those who read the original …

Matchstick miscellany

White propolis

What is propolis for?

Why, when you go to open a hive that you’ve not visited for some time, is the crownboard invariably stuck down with propolis?

Are the bees trying to stop you looking in? Do they think a thin bead of propolis is defence against a well-aimed hive tool?

Of course not.

What they are doing is sealing up every tiny nook and cranny, every gap and interstice.

You might think the crownboard is a snug fit.

The bees don’t.

Even the brand new, smooth, flat plastic interface between an Abelo crownboard and brood box get glued together within days.

Every fissure through which wasps 1 could gain access or heat could escape or water enter or whatever is gummed shut with a liberal helping of propolis.

Propolis is of course also antibacterial and has a host of other great properties, but for the purpose of this post I’m restricting myself to its use as a sort of “No Nonsense Decorators Caulk” of the bee world 2.

Mind the gap

Additional evidence that bees really do ‘mind the gap’ is easy to find if you use crownboards with holes in them.

Not the great gaping opening(s) designed to accommodate a porter bee escape (I’ll return to these shortly), but instead something like the ventilated disks in the grossly over-engineered Abelo poly crownboards.

Abelo poly National crownboard ...

Abelo poly National crownboard …

Here’s a brand new one, just out of the packing, with all the little fiddly ventilated plastic disks and poly plugs to cover them.

And this is what one of those ventilated holes looks like after a few weeks use …

Exhibit A … ventilated hole in an Abelo crownboard

And the same thing applies to wire mesh screens when I use split boards as crownboards (because I’ve run out … even of the 25p polythene ones).

Split board

Split board …

Which end up looking like this …

Exhibit B … are you getting the message?

Matchsticks … don’t try this at home

I’m an increasingly irregular visitor and even less frequent contributor to the online beekeeping discussion forums. On one 3 there’s a perennial discussion thread around this time of year concerning matchsticks.

Matchless matches

Essentially the discussion starts with a question or comment on the need for matchsticks as spacers to separate the crownboard from the brood box during the winter.

You’ll find this advice in many beekeeping books going back more than half a century and you’ll hear it in many ‘Start beekeeping’ winter courses … often taught by beekeepers who learned their beekeeping half a century ago.

In many cases the online forum discussion is started by a recommendation in the monthly BBKA 4 newsletter, or another online forum or Facebook group (again often BBKA-based).

The subsequent ‘discussion’ is generally nothing of the sort. The advice is (in my view rightly) criticised but as much or more effort goes into bashing the BBKA as evidencing why the advice is wrong.

I’m not here to bash the BBKA and I’ve already provided the unequivocal evidence why it’s wrong.

Much better use …

If you provide a narrow space or gap over the top of the colony they will try and seal the gap closed with propolis.

So don’t.

If you want to use matchsticks in the winter … build a model of Notre Dame instead. The bees will appreciate it more.

What are the bees telling you?

The speed with which bees seal up gaps and crevices tells you that that they ‘prefer’ not to have have these types of spaces overhead.

I’m using the word ‘prefer’ here in place of some convoluted justification around evolutionary selection of traits that benefit the long-term survival of the colony and maintenance/transmission of the genes in the environment.

They seal the gaps because to not do so, over eons, is detrimental to Apis mellifera. Not necessarily to that colony per se, but to the species.

Whether they do it to reduce robbing, to stop draughts or rain entering or to prevent the loss of warm air is, in many ways, irrelevant.

Do beekeepers really know better than millions of years of evolution?

No.

The “I always used matchsticks and my bees do well” justification

Is so deeply flawed it barely deserves contradicting.

But since I’m here, I will.

Bees have a fantastic ability to survive and even flourish despite the most cackhanded fumbling by beekeepers 5.

Just because your bees overwintered successfully with a gaping void in the crownboard does not mean they need that gaping void to survive 6.

Observe what the bees do and apply it to your beekeeping.

But what about crownboards with a big hole in for a porter bee escape? The bees don’t block those with propolis.

No, they don’t. But that’s still not justification to leave a void above the cluster. Bees seal gaps smaller than ‘bee space’ (say 8-9 mm) with propolis.

Perhaps they don’t seal up these large holes in the crownboard because the ‘triggers’ that make them seal smaller gaps aren’t present.

As an aside, I wonder if they deploy guard bees to defend these large holes above the cluster? 7

But back to the matchsticks; these create a gap significantly less than 8mm and the bees clearly demonstrate – each and every time you crack open the crownboard – that this is far from optimal.

I’m not going to get into the chimney effect, lost heat, holes in trees, water ingress, draughts etc.

Whether it’s a good idea to ventilate the winter cluster, to get rid of excess humidity or anything else, the evidence is compelling 8the bees would rather you didn’t.

Winter preparation miscellany

The two propolis-adorned crownboard pictures above were taken during an apiary visit in mid-October. I was opening hives for the final time this year. It was 12-13°C and bees were flying, bringing back pollen I presumed was largely from the ivy flowering nearby.

They fancied that fondant

Most had finished their final half block of fondant. The empty wrapper, eke and QE 9 were removed.

Others still had fondant left. In this case I bodily lifted off the QE, fondant and eke/super to give me access to the brood box.

Unfinished fondant

If you feed fondant above a QE you can balance it on an eke or empty super, so avoiding crushing the hundreds of bees clustered underneath the fondant 10

And the reason I needed access to the brood box was to recover the Apivar strips.

If the strip is fixed near the top of the frame this takes just seconds and a small amount of dexterity with a suitable hive tool.

The strips also have a small hole top and centre allowing them to be hung between frames on a matchstick.

But I don’t have matchsticks in the apiary 😉 so instead use the spike to fix them in the comb.

Apivar strips should not be left in for longer than the approved treatment period (6 – 10 weeks; these went in on the 28th of August, so are being removed after 7 weeks). This is important to avoid the reduced levels of amitraz in the ageing strips selecting for Apivar-resistant mites.

The few colonies I checked more thoroughly had little or no brood. All boxes were reassuringly heavy.

I saw a single drone amongst the dozen or so colonies I opened. Not long for this world I fear.

Since there was still pollen coming in I delayed fitting mouseguards to the colonies that need them.

I’ll deal with that once the frosts start 11.

Not long now 🙁


 

Crime doesn’t pay

At least, sometimes it doesn’t.

In particular, the crime of robbery can have unintended and catastrophic consequences.

The Varroa mite was introduced to England in 1992. Since then it has spread throughout most of the UK.

Inevitably some of this spread has been through the activities of beekeepers physically relocating colonies from one site to another.

However, it is also very clear that mites can move from colony to colony through one or more routes.

Last week I described the indirect transmission of a mite ‘left’ by one bee on something in the environment – like a flower – and how it could climb onto the back of another passing bee from a different colony.

Mite transmission routes

As a consequence colony to colony transmission could occur. Remember that a single mite (assuming she is a mated female, which are the only type of phoretic mites) is sufficient to infest a mite-free hive.

However, this indirect route is unlikely to be very efficient. It depends upon a range of rather infrequent or inefficient events 1. In fact, I’m unaware of any formal proof that this mechanism is of any real relevance in inter-hive transmission.

Just because it could happened does not mean it does happen … and just because it does happen doesn’t mean it’s a significant route for mite transmission.

This week we’ll look at the direct transmission routes of drifting and robbing. This is timely as:

  • The early autumn (i.e. now) is the most important time of year for direct transmission.
  • Thomas Seeley has recently published a comparative study of the two processes 2. As usual it is a simple and rather elegant set of experiments based upon clear hypotheses.

Studying phoretic mite transmission routes

There have been several previous studies of mite transmission.

Usually these involve a ‘bait’ or ‘acceptor’ hive that is continuously treated with miticides. Once the initial mite infestation is cleared any new dead mites appearing on the tray underneath the open mesh floor must have been introduced from outside the hive.

All perfectly logical and a satisfactory way of studying mite acquisition.

However, this is not a practical way of distinguishing between mites acquired passively through drifting, with those acquired actively by robbing.

  • Drifting being the process by which bees originating from other (donor) hives arrive at and enter the acceptor hive.
  • Robbing being the process by which bees from the acceptor hive force entry into a donor hive to steal stores.

To achieve this Peck and Seeley established a donor apiary containing three heavily mite-infested hives of yellow bees (headed by Italian queens). These are labelled MDC (mite donor ccolony) A, B and C in the figure below. This apiary was situated in a largely bee-free area.

They then introduced six mite-free receptor colonies (MRC) to the area. Three were located to the east of the donor hives, at 0.5m, 50m and 300m distance. Three more were located – at the same distances – to the west of the donor apiary. These hives contained dark-coloured bees headed by Carniolan queens.

Apiary setup containing mite donor colonies (MDR) and location of mite receptor colonies (MRC).

Peck and Seeley monitored mite acquisition by the acceptor hives over time, fighting and robbing dynamics, drifting workers (and drones) and colony survival.

Test a simple hypothesis

The underlying hypothesis on the relative importance of robbing or drifting for mite acquisition was this:

If drifting is the primary mechanism of mite transmission you would expect to see a gradual increase of mites in acceptor colonies. Since it is mainly bees on orientation flights that drift (and assuming the egg laying rate of the queen is constant) this gradual acquisition of motes would be expected to occur at a constant rate.

Conversely, if robbing is the primary mechanism of mite transmission from mite-infested to mite-free colonies you would expect to see a sudden increase in mite number in the acceptor hives. This would coincide with the onset of robbing.

Graphically this could (at enormous personal expense and sacrifice) be represented like this.

Mite acquisition by drifting (dashed line) or robbing (solid line) over time (t) – hypothesis.

X indicates the time at which the mite-free acceptor colonies are introduced to the environment containing the mite-riddled donor hives.

These studies were conducted in late summer/early autumn at Ithaca in New York State (latitude 42° N). The MDC’s were established with high mite loads (1-3 mites/300 bees in mid-May) and moved to the donor apiary in mid-August. At the same time the MRC’s were moved to their experimental locations. Colonies were then monitored throughout the autumn (fall) and into the winter.

So what happened?

Simplistically, the three mite donor colonies (MDC … remember?) all collapsed and died between early October and early November. In addition, by mid-February the following year four of the six MRC’s had also died.

In every case, colony death was attributed to mites and mite-transmitted viruses. For example, there was no evidence for starvation, queen failure or moisture damage.

But ‘counting the corpses‘ doesn’t tell us anything about how the mites were acquired by the acceptor colonies, or whether worker drifting and/or robbing was implicated. For this we need to look in more detail at the results.

Mite counts

Mite counts in donor (A) and receptor (B, C) colonies.

There’s a lot of detail in this figure. In donor colonies (A, top panel) phoretic mite counts increased through August and September, dropping precipitously from mid/late September.

This drop neatly coincided with the onset of fighting at colony entrances (black dotted and dashed vertical lines). The fact that yellow and black bees were fighting is clear evidence that these donor colonies were being robbed, with the robbing intensity peaking at the end of September (black dashed line). I’ll return to robbing below.

In the receptor colonies the significant increase in mite numbers (B and C) coincided with a) the onset of robbing and b) the drop in mite numbers in the donor colonies.

Phoretic mite numbers in receptor colonies then dropped to intermediate levels in October before rising again towards the end of the year.

The authors do loads of statistical analysis – one-way ANOVA’s, post-hoc Wilcoxon Signed-Rank tests and all the rest 3 and the data, despite involving relatively small numbers of colonies and observations, is pretty compelling.

Robbery

So this looks like robbing is the route by which mites are transmitted.

A policeman would still want to demonstrate the criminal was at the scene of the crime.

Just because the robbing bees were dark doesn’t ‘prove’ they were the Carniolans from the MRC’s 4. Peck and Seeley used a 400+ year old ‘trick’ to investigate this.

To identify the source of the robbers the authors dusted all the bees at the hive entrance with powdered sugar. They did this on a day of intense robbing and then monitored the hive entrances of the MRC’s. When tested, 1-2% of the returning bees had evidence of sugar dusting.

Returning robbers were identified at all the MRC’s. Numbers (percentages) were small, but there appeared to be no significant differences between nearby and distant MRC’s..

Drifting workers and drones

The evidence above suggests that robbing is a major cause of mite acquisition during the autumn.

However, it does not exclude drifting from also contributing to the process. Since the bees in the MDC and MRC were different colours this could also be monitored.

Yellow bees recorded at the entrances of the dark bee mite receptor colonies.

Before the onset of significant robbing (mid-September) relatively few yellow bees had drifted to the mite receptor colonies (~1-2% of bees at the entrances of the MRC’s). The intense robbing in late September coincided with with a significant increase in yellow bees drifting to the MRC’s.

Drifting over at least 50 metres was observed, with ~6% of workers entering the MRC’s being derived from the MDC’s.

If you refer back to the phoretic mite load in the donor colonies by late September (15-25%, see above) it suggests that perhaps 1% of all 5 the bees entering the mite receptor colonies may have been carrying mites.

And this is in addition to the returning robbers carrying an extra payload.

Since the drones were also distinctively coloured, their drifting could also be recorded.

Drones drifted bi-directionally. Between 12 and 22% of drones at hive entrances were of a different colour morph to the workers in the colony. Over 90% of this drone drifting was over short distances, with fewer than 1% of drones at the receptor colonies 50 or 300 m away from the donor apiary being yellow.

Discussion and conclusions

This was a simple and elegant experiment. It provides compelling evidence that robbing of weak, collapsing colonies is likely to be the primary source of mite acquisition in late summer/early autumn.

It also demonstrates that drifting, particularly over short distances, is likely to contribute significant levels of mite transmission before robbing in earnest starts. However, once collapsing colonies are subjected to intense robbing this become the predominant route of mite transmission.

There were a few surprises in the paper (in my view).

One of the characteristics of colonies being intensely robbed is the maelstrom of bees fighting at the hive entrance. This is not a few bees having a stramash 6 on the landing board. Instead it involves hundreds of bees fighting until the robbed colony is depleted of guards and the robbers move in mob handed.

As a beekeeper it’s a rather distressing sight (and must be much worse for the overwhelmed guards … ).

I was therefore surprised that only 1-2% of the bees returning to the mite receptor colonies carried evidence (dusted sugar) that they’d been involved in robbing. Of course, this could still be very many bees if the robbing colonies were very strong. Nevertheless, it still seemed like a small proportion to me.

It’s long been known that mites and viruses kill colonies. However, notice how quickly they kill the mite receptor colonies in these studies.

The MRC’s were established in May with very low mite numbers. By the start of the experiment (mid-August) they had <1% phoretic mites. By the following spring two thirds of them were dead after they had acquired mites by robbing (and drifting) from nearby collapsing colonies 7.

It doesn’t take long

The science and practical beekeeping

This paper confirms and reinforces several previous studies, and provides additional evidence of the importance of robbing in mite transmission.

What does this mean for practical beekeeping?

It suggests that the late-season colonies bulging with hungry bees that are likely to initiate robbing are perhaps most at risk of acquiring mites from nearby collapsing colonies.

This is ironic as most beekeepers put emphasis on having strong colonies going into the winter for good overwintering success. Two-thirds of the colonies that did the robbing died overwinter.

The paper emphasises the impact of hive separation. Drifting of drones and workers was predominantly over short distances, at least until the robbing frenzy started.

This suggests that colonies closely situated within an apiary are ‘at risk’ should one of them have high mite levels (irrespective of the level of robbing).

If you treat with a miticide, treat all co-located colonies.

However, drifting over 300 m was also observed. This implies that apiaries need to be well separated. If your neighbour has bees in the next field they are at risk if you don’t minimise your mite levels … or vice versa of course.

And this robbing occurred over at least 300 m and has been reported to occur over longer distances 8. This again emphasises both the need to separate apiaries and to treat all colonies in a geographic area coordinately.

Most beekeepers are aware of strategies to reduce robbing i.e. to stop colonies being robbed. This includes keeping strong colonies, reduced entrances or entrance screens.

But how do you stop a strong colony from robbing nearby weak colonies?

Does feeding early help?

I don’t know, but it’s perhaps worth considering. I don’t see how it could be harmful.

I feed within a few days of the summer honey supers coming off. I don’t bother waiting for the bees to exploit local late season forage. They might anyway, but I give them a huge lump of fondant to keep them occupied.

Do my colonies benefit, not only from the fondant, but also from a reduced need to rob nearby weak colonies?

Who knows?

But it’s an interesting thought …

Note there’s an additional route of mite transmission not covered in this or the last post. If you transfer frames of brood from a mite-infested to a low mite colony – for example, to strengthen a colony in preparation for winter – you also transfer the mites. Be careful.


Colophon

The idiom “Crime doesn’t pay” was, at one time, the motto of the FBI and was popularised by the cartoon character Dick Tracy.

Woody Allen in Take the Money and Run used the quote “I think crime pays. The hours are good, you travel a lot.”

Cabinet reshuffle

Don’t worry, this isn’t a post about the totally dysfunctional state of British politics at the moment 1.

Once the honey supers are removed there’s seemingly little to do in the apiary. There is a temptation to catch up on all those other jobs postponed because I was “just off to the bees”.

Well, maybe temptation is a bit strong. After all, like all good procrastinators, I can usually find an excuse to postpone until next week something that could be left until at least tomorrow.

However, as I said last week, preparations for winter are very important and should not be delayed.

I covered feeding and the all-important late summer mite treatments in that post. Here I’m going to briefly discuss the various late season hive rearrangements that might be needed.

Clearing additional supers

I use very simple clearer boards to get the bees out of my supers. However, there are a couple of instances when not all the supers end up being removed:

  1. If some frames are empty or fail the ‘shake test’ I’ll rearrange these into the bottom super 2. I then clear the bees down into the bottom super and leave it for the bees.
  2. If the colony is really strong and is unlikely to fit into the brood box(es) I’ll often add a super above the queen excluder to clear the bees down into. Sometimes the bees will add a few dribbles of nectar to this … not enough to ever extract, and I’d prefer they put it in the brood box instead.

In both these situations I’ll want to remove the additional super before winter. I don’t want the bees to have a cold empty space above their heads.

Feed & clear together

I usually do this at the same time that I feed the bees.

I rearrange the boxes so that the ‘leftover’ super is above a crownboard on top of the super that is providing the headspace to accommodate the fondant blocks.

Since access to this top super is through a small hole the bees consider it is ‘outside’ the hive and so empty the remaining nectar and bring it down to the brood box 3.

If there are sealed stores in any of these super frames I bruise 4 the cappings with a hive tool and they’ll then move the stores down.

Substandard colonies

A very good piece of advice to all beekeepers is to “take your winter losses in the autumn”. This means assess colonies in the late summer/early autumn and get rid of those that are weak or substandard 5.

Substandard might mean those with a poor temper.

This is the colony which you put up with all season (despite their yobbo tendencies) because you believe that aggressive bees are productive bees’.

Were they?

Was that one half-filled super of partially-capped honey really worth the grief they gave you all summer?

Unless substandard (not just aggression … running, following, insufficiently frugal in winter etc.) colonies are replaced the overall standard of your bees will never improve.

I’ll discuss how to ‘remove’ them in a few paragraphs.

It’s probably a reasonable estimate to suggest that the ‘best’ third of your colonies should be used to rear more queens and the ‘worst’ third should be re-queened with these 6.

Over time 7 the quality will improve.

Of course, a substandard colony might well make it through the winter perfectly successfully. The same cannot be said for weak colonies.

TLC or tough love?

At the end of the summer colonies should be strong. If they are not then there is probably something wrong. A poorly mated queen, an old and failing queen, disease?

The exception might be a recently requeened colony or a new 5 frame nuc.

Everynuc

Everynuc …

Colonies that are weak at this stage of the season for no obvious reason need attention. Without it they are likely to succumb during the winter. And they’ll do this after you’ve gone to the trouble and expense of feeding and treating them … 8

There are essentially two choices:

  1. Mollycoddle them and hope they pick up. Boosting them with a frame or two of emerging brood may help (but make sure you don’t weaken the donor colony significantly). Moving them from a full hive to a nuc – preferably poly to provide better insulation – may also be beneficial. In a nuc they have less dead space to heat. An analogous strategy is to fill the space in the brood box with ‘fat dummies‘ or – low-tech but just as effective – a big wodge of bubble wrap with a standard dummy board to hold it in place.
  2. Sacrifice the queen from the weak hive and unite them with a strong colony.

Sentimentalism

Of the two I’d almost always recommend uniting colonies.

It’s less work. There’s no potentially wasted outlay on food and miticides. Most importantly, it’s much more likely to result in a strong colony the following spring.

However, we all get attached to our bees. It’s not unusual to give a fading favourite old queen ‘one more chance’ in the hope that next year will be her last hurrah.

Uniting notes

I’ve covered uniting before and so will only add some additional notes here …

Uniting a nuc with a full colony

Uniting a nuc with a full colony …

  • You cannot generate a strong colony by uniting two weak colonies. They’re weak for a reason. Whether they’re weak for the same or different reasons uniting them is unlikely to help.
  • Never unite a colony with signs of disease. All you do is jeopardise the healthy colony.
  • Find the queen and permanently remove her from the weak or poor quality (substandard) colony.
  • If you can’t find the queen unite them with a queen excluder between the colonies. In my limited experience (I usually manage to find the unwanted queen) the bees usually do away with a failing queen when offered a better one, but best to check in a week or so.
  • I generally move the de-queened colony and put it on top of the strong queenright colony.
  • Unite over newspaper and don’t interfere with the hive for at least another week.
  • You can unite one strong colony and two weak colonies simultaneously.
  • Uniting and feeding at the same time is possible.
  • You can unite and treat with a miticide like Amitraz simultaneously. You will have to make a judgement call on whether both boxes need miticide treatment, depending on the strength of the weak colony.
  • If you’re uniting a strong substandard colony and a strong good colony you will need to use an amount of miticide appropriate for a double brood colony (four strips in the case of Amitraz).
Successful uniting ...

Successful uniting …

Season of mists and mellow fruitfulness

The goal of all of the above is to go into autumn with strong, healthy, well-fed colonies that will survive the winter and build up strongly again in the spring.

A very small or weak colony 9 in autumn may survive, but it’s unlikely to flourish the following spring.

“It takes bees to make bees.”

And a weak colony in spring lacks bees, so cannot build up fast.

In contrast, an overwintered strong colony can often yield a nuc in May the following year. You’ve regained your colony numbers, but have a new, young queen in one hive with most of the season ahead for her to prove her worth.

I’ve merged three topics here – clearing supers, stock improvement and getting rid of weak colonies before winter – because all involve some sort of hive manipulation in the early autumn. I usually complete this in late September or early October, with the intention of overwintering strong colonies in single brood boxes packed with bees and stores.


Colophon

The heading of the final paragraph is the opening line of To Autumn by John Keats (1795-1821). Keats wrote To Autumn exactly two hundred years ago (September 1819, his last poem) while gradually succumbing to tuberculosis. Despite this, and his doomed relationship with Fanny Brawne, the poem is not about sadness at the end of summer but instead revels in the ripeness and bounteousness of the season.

Of course, all beekeepers know that the first stanza of To Autumn closes with a reference to bees.

Season of mists and mellow fruitfulness,
  Close bosom-friend of the maturing sun;
Conspiring with him how to load and bless
  With fruit the vines that round the thatch-eves run;
To bend with apples the moss’d cottage-trees,
  And fill all fruit with ripeness to the core;
    To swell the gourd, and plump the hazel shells
  With a sweet kernel; to set budding more,
And still more, later flowers for the bees,
Until they think warm days will never cease,
    For summer has o’er-brimm’d their clammy cells.

 

The flow must go on

Except it doesn’t 🙁

And once the summer nectar flow is over, the honey ripened and the supers safely removed it is time to prepare the colonies for the winter ahead.

It might seem that mid/late August is very early to be thinking about this when the first frosts are probably still 10-12 weeks away. There may even be the possibility of some Himalayan balsam or, further south than here in Fife, late season ivy.

However, the winter preparations are arguably the most important time in the beekeeping year. If you leave it too late there’s a good chance that colonies will struggle with disease, starvation or a toxic combination of the two.

Long-lived bees

The egg laying rate of the queen drops significantly in late summer. I used this graph recently when discussing drones, but look carefully at the upper line with open symbols (worker brood). This data is for Aberdeen, so if you’re beekeeping in Totnes, or Toulouse, it’ll be later in the calendar. But it will be a broadly similar shape.

Seasonal production of sealed brood in Aberdeen, Scotland.

Worker brood production is down by ~75% when early July and early September are compared.

Not only are the numbers of bees dropping, but their fate is very different as well.

The worker bees reared in early July probably expired while foraging in late August. Those being reared in early September might still be alive and well in February or March.

These are the ‘winter bees‘ that maintain the colony through the cold, dark months so ensuring it is able to develop strongly the following spring.

The purpose of winter preparations is threefold:

    1. Encourage the colony to produce good numbers of winter bees
    2. Make sure they have sufficient stores to get through the winter
    3. Minimise Varroa levels to ensure winter bee longevity

I’ll deal with these in reverse order.

Varroa and viruses

The greatest threat to honey bees is the toxic stew of viruses transmitted by the Varroa mite. Chief amongst these is deformed wing virus (DWV) that results in developmental abnormalities in heavily infected brood.

DWV is well-tolerated by honey bees in the absence of Varroa. The virus is probably predominantly transmitted between bees during feeding, replicating in the gut but not spreading systemically.

However, Varroa transmits the virus when it feeds on haemolymph (or is it the fat body?), so bypassing any protective immune responses that occur in the gut. Consequently the virus can reach all sorts of other sensitive tissues resulting in the symptoms most beekeepers are all too familiar with.

Worker bee with DWV symptoms

Worker bee with DWV symptoms

However, some bees have very high levels of virus but no overt symptoms 1.

But they’re not necessarily healthy …

Several studies have clearly demonstrated that colonies with high levels of Varroa and DWV are much more likely to succumb during the winter 2.

This is because deformed wing virus reduces the longevity of winter bees. Knowing this, the increased winter losses make sense; colonies die because they ‘run out’ of bees to protect the queen and/or early developing brood.

I’ve suggested previously that isolation starvation may actually be the result of large numbers of winter bees dying because of high DWV levels. If the cluster hadn’t shrunk so much they’d still be in contact with the stores.

Even if they stagger on until the spring, colony build up will be slow and faltering and the hive is unlikely to be productive.

Protecting winter bees

The most read article on this site is When to treat? This provides all the gory details and is worth reading to get a better appreciation of the subject.

However, the two most important points have already been made in this post. Winter bees are being reared from late August/early September and their longevity depends upon protecting them from Varroa and DWV.

To minimise exposure to Varroa and DWV you must therefore ensure that mite levels are reduced significantly in late summer.

Since most miticides are incompatible with honey production this means treating very soon after the supers are removed 3.

Time of treatment and mite numbers

Time of treatment and mite numbers

Once the supers are off there’s nothing to be gained by delaying treatment … other than more mite-exposed bees 🙁

In the graph above the period during which winter bees are being reared is the green arrow between days 240 and 300 (essentially September and October). Mite levels are indicated with solid lines, coloured according to the month of treatment. You kill more mites by treating in mid-October (cyan) but the developing winter bees are exposed to higher mite levels.

In absolute numbers more mites are present and killed because they’ve had longer to replicate … on your developing winter bee pupae 🙁

Full details and a complete explanation is provided in When to treat?

So, once the supers are off, treat as early as is practical. Don’t delay until late September or early October 4.

Treat with what?

As long as it’s effective and used properly I don’t think it matters too much.

Amitraz strip placed in the hive.

Apiguard if it’s warm enough. Apistan if there’s no resistance to pyrethroids in the local mite population (there probably will be 🙁 ). Amitraz or even multiple doses of vaporised oxalic acid-containing miticide such as Api-Bioxal 5.

This year I’ve exclusively used Amitraz (Apivar). It’s readily available, very straightforward to use and extremely effective. There’s little well-documented resistance and it does not leave residues in the comb.

The same comments could be made for Apiguard though the weather cannot be relied upon to remain warm enough for its use here in Scotland.

Another reason to not use Apiguard is that it is often poorly tolerated by the queen who promptly stops laying … just when you want her to lay lots of eggs to hatch and develop into winter bees 6.

Feed ’em up

The summer nectar has dried up. You’ve also removed the supers for extraction.

Colonies are likely to be packed with bees and to be low on stores.

Should the weather prevent foraging there’s a real chance colonies might starve 7 so it makes sense to feed them promptly.

The colony will need ~20 kg (or more) of stores to get through the winter. The amount needed will be influenced by the bees 8, the climate and how well insulated the hive is.

I only feed my bees fondant. Some consider this unusual 9, but it suits me, my beekeeping … and my bees.

Bought in bulk, fondant (this year) costs £10.55 for a 12.5 kg block. Assuming there are some stores already in the hive this means I need one to one and a half blocks per colony (i.e. about £16).

These three photographs show a few of the reasons why I only use fondant.

  • It’s prepackaged and ready to use. Nothing to make up. Just remove the cardboard box.
  • Preparation is simplicity itself … just slice it in half with a long sharp knife. Or use a spade.
  • Open the block like a book and invert over a queen excluder. Use an empty super to provide headroom and then replace the crownboard and roof.
  • That’s it. You’re done. Have a holiday 😉
  • The timings shown above are real … and there were a couple of additional photos not used. From opening the cardboard box to adding back the roof took less than 90 seconds. And that includes me taking the photos and cutting the block in half 🙂
  • But equally important is what is not shown in the photographs.
    • No standing over a stove making up gallons of syrup for days in advance.
    • There is no specialist or additional equipment needed. For example, there are no bulky syrup feeders to store for 48 weeks of the year.
    • No spilt syrup to attract wasps.
    • Boxed, fondant keeps for ages. Some of the boxes I used this year were purchased in 2017.
    • The empty boxes are ideal for customers to carry away the honey they have purchased from you 😉
  • The final thing not shown relates to how quickly it is taken down by the bees and is discussed below.

I’m surprised more beekeepers don’t purchase fondant in bulk through their associations and take advantage of the convenience it offers. By the pallet-load delivery is usually free.

Fancy fondant

Capped honey is about 82% sugar by weight. Fondant is pretty close to this at about 78%. Thick syrup (2:1 by weight) is 66% sugar.

Therefore to feed equivalent amounts of sugar for winter you need a greater weight of syrup. Which – assuming you’re not buying it pre-made – means you have to prepare and carry large volumes (and weights) of syrup.

Meaning containers to clean and store.

But consider what the bees have to do with the sugar you provide. They have to take it down into the brood box and store it in a form that does not ferment.

Fermenting stores can cause dysentry. This is ‘a bad thing’ if you are trapped by adverse weather in a hive with 10,000 close relatives … who also have dysentry. Ewww 😯

To reduce the water content the bees use space and energy. Space to store the syrup and energy to evaporate off the excess water.

Bees usually take syrup down very fast, rapidly filling the brood box.

In contrast, fondant is taken down more slowly. This means there is no risk that the queen will run out of space for egg laying. Whilst I’ve not done any side-by-side properly controlled studies – or even improperly controlled ones – the impression I have is that feeding fondant helps the colony rear brood into the autumn 10.

Whatever you might read elsewhere, bees do store fondant. The blocks I added this week will just be crinkly blue plastic husks by late September, and the hives will be correspondingly heavier.

You can purchase fancy fondant prepared for bees with pollen and other additives.

Don’t bother.

Regular ‘Bakers Fondant’ sold to ice Chelsea buns is the stuff to use. All the colonies I inspect at this time of the season have ample pollen stores.

I cannot comment on the statements made about the anti-caking agents in bakers fondant being “very bad for bees” … suffice to say I’ve used fondant for almost a decade with no apparent ill-effects 11.

It’s worth noting that these statements are usually made by beekeeping suppliers justifying selling “beekeeping” fondant for £21 to £36 for 12.5 kg.

Project Fear?


Colophon

The title of this post is a mangling of the well-known phrase The show must go on. This probably originated with circuses in the 19th Century and was subsequently used in the hotel trade and in show business.

The show must go on is also the title of (different) songs by Leo Sayer (in 1973, his first hit record, not one in my collection), Pink Floyd (1979, from The Wall) and Queen (1991).

Women without men

The title of the post last week was The end is nigh which, looking at the fate of drones this week, was prophetic.

Shallow depth of field

Watch your back mate … !

After the ‘June gap’ ended queens started laying again with gusto. However, there are differences in the pattern of egg laying when compared to the late spring and early summer.

Inspections in mid/late August 1 show clear signs of colonies making preparations for the winter ahead.

For at least a month the amount of drone brood in colonies has been reducing (though the proportions do not change dramatically). As drones emerge the cells are being back-filled with nectar.

Seasonal production of sealed brood in Aberdeen, Scotland.

The data in the graph above was collected over 50 years ago 2. It remains equally valid today with the usual caveats about year-to-year variation, the influence of latitude and local climate.

Drones are valuable …

Drones are vital to the health of the colony.

Honey bees are polyandrous, meaning the queen mates with multiple males so increasing the genetic diversity of the resulting workers.

There are well documented associations between colony fitness and polyandry, including improvements in population growth, weight gain (foraging efficiency) and disease resistance.

The average number of drones mating with a queen is probably somewhere between 12 and 15 under real world conditions. However studies have shown that hyperpolyandry further enhances the benefits of polyandry. Instrumentally inseminated queens “mated” with 30 or 60 drones show greater numbers of brood per bee and reduced levels of Varroa infestation.

Why don’t queens always mate with 30-60 drones then?

Presumably this is a balance between access, predation and availability of drones. For example, more mating would likely necessitate a longer visit to a drone congregation area so increasing the chance of predation.

In addition, increasing the numbers of matings might necessitate increasing the number of drones available for mating 3.

… and expensive

But there’s a cost to increasing the numbers of drones.

Colonies already invest a huge amount in drone rearing. If you consider that this investment is for colony reproduction it is possible to make comparisons with the investment made in workers for reproduction i.e. the swarm that represents the reproductive unit of the colony.

Comparison of the numbers of workers or drones alone is insufficient. As the graph above shows, workers clearly outnumber drones. Remember that drones are significantly bigger than workers. In addition, some workers are not part of the ‘reproductive unit’ (the swarm).

A better comparison is between the dry weight of workers in a swarm and the drones produced by a colony during the season.

It’s worth noting that these comparisons must be made on colonies that make as many drones as they want. Many beekeepers artificially reduce the drone population by only providing worker foundation or culling drone brood (which I will return to later).

In natural colonies the dry weight of workers and drones involved in colony reproduction is just about 1:1 4.

Smaller numbers of drones are produced, but they are individually larger, live a bit longer and need to be fed through this entire period. That is a big investment.

Your days are numbered

And it’s an investment that is no longer needed once the swarming season is over. All those extra mouths that need feeding are a drain on the colony.

Even though the majority of beekeepers see the occasional drone in an overwintering colony, the vast majority of drones are ejected from the hive in late summer or early autumn.

About now in Fife.

In the video above you can see two drones being harassed and evicted. One flies off, the second drops to the ground.

As do many others.

There’s a small, sad pile of dead and dying drones outside the hive entrance at this time of the season. All perfectly normal and not something to worry about 5.

Drones are big, strong bees. These evictions are only possible because the workers have stopped feeding them and they are starved and consequently weakened.

A drone’s life … going out with a bang … or a whimper.

An expense that should be afforded

Some of the original data on colony sex ratios (and absolute numbers) comes from work conducted by Delia Allen in the early 1960’s.

Other colonies in these studies were treated to minimise the numbers of drones reared. Perhaps unexpectedly these colonies did not use the resources (pollen, nectar, bee bread, nurse bee time etc) to rear more worker bees.

In fact, drone-free or low-drone colonies produced more bees overall, a greater weight of bees overall and collected a bit more honey. This strongly suggests that colonies prevented from rearing drones are not able to operate at their maximum potential.

This has interesting implications for our understanding of how resources are divided between drone and worker brood production. It’s obviously not a single ‘pot’ divided according to the numbers of mouths to feed. Rather it suggests that there are independent ‘pots’ dedicated to drone or worker production.

Late season mating and preparations for winter

The summer honey is off and safely in buckets. Colonies are light and a bit lethargic. With little forage about (a bit of balsam and some fireweed perhaps) colonies now need some TLC to prepare them for the winter.

If there’s any reason to delay feeding it’s important that colonies are not allowed to starve. We had a week of bad weather in mid-August. One or two colonies became dangerously light and were given a kilogram of fondant to tide them over until the supers were off all colonies and feeding and treating could begin. I’ll deal with these important activities next week.

In the meantime there are still sufficient drones about to mate with late season queens. The artificial swarm from strong colony in the bee shed was left with a charged, sealed queen cell.

Going by the amount of pollen going in and the fanning workers at the entrance – see the slo-mo movie above – the queen is now mated and the colony will build up sufficiently to overwinter successfully.


Colophon

Men without Women

Men without women was the title of Ernest Hemingway’s second published collection of short stories. They are written in the characteristically pared back, slightly macho and bleak style that Hemingway was famous for.

Many of these stories have a rather unsatisfactory ending.

Not unlike the fate of many of the drones in our colonies.

Women without men is obviously a reworking of the Hemingway title which seemed appropriate considering the gender-balance of colonies going into the winter.

If I’d been restricted to writing using the title Men without Women I’d probably have discussed the wasps that plague our picnics and hives at this time of the year. These are largely males, indulging in an orgy of late-season carbohydrate bingeing.

It doesn’t do them any good … they perish and the hibernating overwintering mated queens single-handedly start a new colony the following spring.

Droning on

This post was supposed to be about Varroa resistance in Apis mellifera – to follow the somewhat controversial ‘Leave and let die’ from a fortnight ago. However, pesky work commitments have prevented me doing it justice so it will have to wait for a future date.

All work and no play …

Instead I’m going to pose some questions (and provide some partial answers) on overwintering mites and the use of drone brood culling to help minimise mite levels early in the season.

Imagine the scenario

A poorly managed colony goes into the winter with very high mite levels. Let’s assume the beekeeper failed to apply a late summer/early autumn treatment early enough and then ignored the advice to treat again in midwinter when the colony is broodless.

Tut, tut …

The queen is laying fewer and fewer eggs as the days shorten and the temperature drops. There are decreasing amounts of the critical 5th instar larvae that the mite must infest to reproduce.

At some point the colony may actually be broodless.

What happens to the mites?

Do they just hang around as phoretic mites waiting for the queen to start laying again?

Presumably, because there is nowhere else they can go … but …

What about the need for nurses?

During the Varroa reproductive cycle newly emerged mites preferentially associate with nurse bees for ~6 days (usually quoted as 4-11 days) before infesting a new 5th instar larva.

Mites that associate with newly emerged bees or bees older than nurse bees exhibit reduced fecundity and fitness i.e. they produce fewer progeny and fewer mature progeny 1 per infested cell.

I’m not aware of studies showing the influence of the physiologically-distinct winter bees on mite fecundity.

Similarly, I’m not sure if there are any studies that have looked at the types of bees phoretic mites associate with during the winter 2, or the numbers of bees in the colony during November to January 3 that might be considered to be similar physiologically to nurse bees.

Whilst we (or at least I) don’t know the answer to these questions, I’m willing to bet – for reasons to be elaborated upon below – that during the winter the fecundity and fitness of mites decreases significantly.

And the number of the little blighters …

Mite longevity

How long does a mite live?

The usual figure quoted for adult female mites is 2-3 reproductive cycles (of ~17 days and ~11 days for the first and subsequent rounds respectively). So perhaps about 40 days in total.

But, in the absence of brood (or if brood is in very short supply) this is probably longer as there is data linking longevity to the number of completed reproductive cycles i.e. if there is no reproduction the mite can live longer.

It is therefore perhaps reasonable to assume that mites should be able to survive through a broodless period of several weeks during midwinter. However, remember that this increases the chance the mite will be removed by grooming or other physical contacts within the cluster, so reducing the overall population.

Spring has sprung

So, going back to the scenario we started with …

What happens in late winter/early spring when the queen starts laying again?

Does that 5cm patch of early worker brood get immediately inundated with hundreds of mites?

If so, the consequences for the early brood are dire. High levels of mite infestation inevitably mean exposure to a large amount of deformed wing virus (DWV) which likely will result in precisely the developmental deformities you’d expect … DWV really “does what it says on the tin”.

Worker bee with DWV symptoms

Worker bee with DWV symptoms

My hives are carefully managed to minimise mite levels. I don’t really have any personal experience to help answer the question. However, in colonies that have higher (or even high) mite levels I don’t think it’s usual to see significant numbers of damaged bees in the very earliest possible inspections of the season 4.

My (un)informed guess …

My guess is that several things probably happen to effectively reduce exposure of this earliest brood to Varroa:

  1. Varroa levels in the colony drop due to the extended winter phoretic phase. More opportunities for grooming or similar physical contact (perhaps even clustering) increase the loss of mites.
  2. Mites that remain may have reduced access to brood simply due to the mathematical chance of the bee they are phoretic on coming into contact with the very small numbers of late stage larvae in the colony.
  3. Mites that do infest brood have reduced fecundity and fitness and may not rear (m)any progeny.

There are a lot of assumptions and guesswork there. Some of these things may be known but discussions I’ve had with some of the leading Varroa researchers suggest that there are still big gaps in our knowledge.

OK, enough droning on, what about drones?

Back to the imagined scenario.

What happens next?

Well, perhaps not next, but soon?

The colony continues to contract (because the daily loss of aged workers still outnumbers the daily gain of new bees) but the laying rate of the queen gradually increases from a few tens, to hundreds to a couple of thousand eggs per day.

And the colony starts to really expand.

And so do the mite numbers …

Pupa (blue) and mite (red) numbers

And at some point, depending upon the expansion rate, the climate and (probably) a host of factors I’ve not thought of or are not known, the colony begins to make early swarm preparations by starting to rear drones.

Drones take 24 days to develop from the egg and a further 12-16 days to reach sexual maturity. If the swarming period starts in the first fortnight of May, the drones that take part were laid as eggs in late March.

And drone larvae are very attractive to Varroa.

9 out of 10 mites prefer drones

Varroa replicates ‘better’ in association with drone pupae. By better I mean that more progeny are produced from each infested cell. This is because the drone replication cycle is longer than that of worker brood.

The replication cycle of Varroa

The replication cycle of Varroa

On average 2.2 new mites are produced in drone cells vs only 1.3 in worker cells 5. From an evolutionary standpoint this is a significant selective pressure and it’s therefore unsurprising that Varroa have evolved to preferentially infest drone brood.

Irrespective of the mite levels, given the choice between worker and drone, Varroa will infest drone brood at 8-11 times the level of worker brood 6.

Significantly, as the amount of drone brood was reduced (typically it’s 5-15% of comb in the hive) the drone cell preference increased by ~50% 7.

I hope you can see where this is now going …

Early drone brood sacrifice

As colony expansion segues into swarm preparation the queen lays small amounts of drone brood. These cells are a very small proportion of the overall brood in the colony but are disproportionately favoured by the mite population.

And the mite population – even in a poorly managed colony – should be less (and less fit) in the Spring than the preceding autumn for reasons elaborated upon above (with the caveat that some of that was informed guesswork).

Therefore, if you make sure you remove the earliest capped drone brood you should also remove a significant proportion of the viable mites in the colony.

Drone brood is usually around the periphery of the brood nest, along the bottom of frames with normal worker foundation, or on the ‘shoulders’ near the lugs. The drone brood is often scattered around the brood nest.

As a consequence, if you want to remove all the earliest capped drone brood you have to rummage through the frames and ‘fork out’ 8 little patches here and there.

It can be a bit of a mess.

Is there an easier way to do this?

Drone cells

Beekeepers who predominantly use foundationless frames will be aware that they usually have significantly more drones (and drone comb) in their colonies than equivalent sized colonies using embossed worker foundation.

Depending upon the type of foundationless frames used the drone comb is drawn out in different positions on the frames.

Horizontally wired foundationless frames can be all drone brood or a mix of drone and worker. However, the demarcation between the brood types is often inconveniently located with regard to support wires.

In contrast, foundationless frames constructed using vertical bamboo supports are often built as ‘panels’ consisting entirely of drone or worker comb.

Drone-worker-drone

Drone-worker-drone …

Which makes slicing out one or more complete panels of recently capped drone brood simplicity itself.

There are no wires in the way.

You can sometimes simply pull it off the starter strip.

Drone brood sacrifice

Check the brood for Varroa 9, feed the pupae to your chickens and/or melt out the wax in your steam wax extractor.

The bees will rapidly rebuild the comb and will not miss a few hundred drones.

They’ll be much healthier without the mites. Importantly, the mites will have been removed from the colony early in the season so preventing them going through repeated rounds of reproduction.

This is the final part of the ‘midseason mite management‘ triptych 10, but I might return to the subject with some more thoughts in the future … for example, continuous culling of drone brood (in contrast to selective culling of the very earliest drone brood in the colony discussed here) is not a particularly effective way of suppressing mite levels in a colony.