Tag Archives: weather

Weather to treat

Not Whether to treat? … to which the answer is yes. Instead, a poor pun on the choice of how I use temperature as an indication of when to treat colonies in midwinter …

Midwinter OA-based treatments

Oxalic acid-based treatments for midwinter Varroa control are most effective when colonies are broodless. This is because oxalic acid (OA) treatments only kill phoretic mites and are ineffective against mites in sealed cells. They are therefore ideal for use on swarms, packages and broodless colonies in midwinter.

These OA treatments include Api-Bioxal, the VMD-approved treatment, and unmodified oxalic acid, it’s active ingredient. The importance of midwinter treatments, the preparation of the OA solution and how to trickle treat have recently been covered. I’ve previously discussed sublimation and will do so again in a longer article in the future.

The beekeepers winter dilemma

How can you tell whether your colonies are broodless in midwinter?

On a warm, sunny, Spring afternoon this takes just a couple of minutes … remove the roof, crack off the crownboard, gently lift out the dummy board and the adjacent frame, look carefully at the mass of bees covering the top bars, aim for about the middle and gently prise apart those two frames, lift out a frame from one side of the ‘gap’ and – Hey presto – brood.

Just writing that in early December makes me hanker for much warmer days …

Memories of midseason

Memories of midseason

Actually, you can do exactly the same in midwinter. There are videos on the internet showing an experienced and (in)famous Finnish beekeeper opening his colonies at -10ºC.

I’ve opened and briefly inspected colonies at low temperatures (though not sub-zero). The bees are usually pretty torpid, reluctant to fly – or simply too cold to – and you can be in and out in just a minute or so. Bees cope pretty well with this. It undoubtedly disturbs them a bit and it breaks the propolis seal on the crownboard, but – done carefully and quickly – it’s the only foolproof way to determine whether a colony is broodless in midwinter.

But what if they’ve got brood and it’s therefore not the optimal time to treat? Do you go back and repeat the entire process in 1-2 weeks? What if it’s snowing next time, or there’s a howling gale blowing?

An alternative approach is needed.

The annual brood rearing cycle

As the colony moves from summer to autumn the egg laying rate of the queen drops. It goes on dropping, although not necessarily smoothly, as the days shorten further, the temperature drops and the sources of pollen and nectar disappear. If the queen stops laying altogether then the colony will become broodless about 21 days later.

At some point, perhaps early in the New Year, the queen starts laying again. Slowly at first, but at increasing levels as the season starts. Once foraging starts in earnest the egg laying rate increases markedly and peaks sometime in June.

The precise timing of all these changes cannot be predicted. It’s likely to be dependent on a range of factors – nectar and pollen availability, the strain of bee, day length (and whether it’s increasing or decreasing) and temperature.

Of these, temperature probably has the greatest influence.


Generalised annual brood and worker numbers ...

Generalised annual brood and worker numbers …

Here’s a quick’n’dirty graph put together with BEEHAVE showing a generalised annual cycle of total brood (blue) and adult bee (red) numbers. Under the conditions in this model the colony is broodless for ~30 days at the end if the year.


Part of the problem with being definitive about the annual brood cycle is the temperature variation with latitude. Temperate regions stretch – in Europe – from Northern Finland to Southern Spain. Bees are kept throughout this range, but obviously experience wildly different climates.

And then there’s the year to year variation.

So if you can’t predict when the colony is going to be broodless, perhaps you can observe the weather – and in particular the temperature – and make an educated guess.

Watch the weather

Over the last few years I’ve applied my midwinter treatment soon (<6 days) after the end of the first extended cold period of the season. This is generally earlier than most beekeepers, who often treat between Christmas and New Year, or early in January.

So, how do we reasonably accurately monitor the weather for a suitable time to treat?

Ho ho ho

Ho ho ho

Most of us live in centrally-heated splendour, protected from the day-to-variation of temperature by heated car seats, air conditioning, hot water bottles, Thinsulate and wood-burning stoves. Do you know what the temperature was today? Rather than trust the wildly-variable (in accuracy) national weather reports for the actual temperature near my apiaries, I instead use very much more local data from Weather Underground.

There are hundreds of ‘amateur’ weather stations across the country that upload data to wunderground.com. Most of these provide current and historic data, including temperature (max, min and average). Here’s one for Auchtermuchty in Fife (on wunderground.com) and directly from the weather station.

Once the weather cools I keep an eye on the average temperature over an extended period of a fortnight or so. If it remains low I wait a bit more … but I then treat as soon as practical after it warms up to 8-10°C or so.

The proof of the pudding

Here’s a graph of the temperature data for 2016§. As indicated on the graph, I treated colonies on the 7th of December.

2016 temperature data and OA treatment ...

2016 temperature data and OA treatment …

I didn’t open my colonies, but others opened on the same day nearby were all broodless. The 7th was chosen as it was the first warm (relatively!) day after a 19 day window in which the average temperature had barely climbed above 5°C.

These treated colonies went into the New Year with vanishingly low Varroa levels.

And again …

This year appears to be repeating a very similar pattern. We’ve had frosts most nights since the 10th of November. It started to warm up significantly in early December as storm Caroline bore down on Scotland and I treated most of my colonies on the 6th 

… by the light of a head torch, in light rain and strengthening wing at 7pm after work.

No, I didn’t open any of the hives to check if they were broodless  😉

It was over 11°C in the apiary when I treated, the barometer was plummeting and the forecast was for near-zero temperatures within 24 hours and remaining that way for another 10 days.

Some of my hives have perspex crownboards. These allow me to check both the state of the colony and if the vapour from my Sublimox has permeated to every corner of the hive. All the colonies were very loosely clustered, with a few bees even wandering out briefly onto the landing board in the dark as I bumbled around preparing things.

The Varroa trays will now be checked in a week or so to work out the mite infestation levels. In the meantime, I can start planning for the coming season knowing I’ve done the best I can to reduce virus levels in the colonies, so giving them a good start to the year.

A Hi tech solution?

Colonies rearing brood maintain a higher, and stable, broodnest temperature (32-35°C) than colonies without brood. It is therefore possible to determine whether a colony has brood by monitoring the temperature directly, rather than trying to infer it from the ambient temperature.

Brood rearing starts ...

Brood rearing starts …

Arnia make hive monitors that allow this sort of thing to be measured. It would be interesting to relate the brood temperature to the ambient temperature (described above) to determine how accurate or otherwise simply ‘watching the weather’ is. Of course … what you’d really want to do is monitor when brood rearing stops and treat soon after that.

Stop press

I treated colonies in our research apiary the following day – the 7th – with dribbled Api-Bioxal. The temperature had dropped almost 7°C since the previous evening and colonies were again beginning to cluster tightly. Under these conditions I’m never confident that the OA vapour penetrates fully, so prefer to trickle treat.

I briefly checked one strong colony in a poly hive for brood.

It was broodless, as I’d hoped  🙂

Of course, this doesn’t guarantee all the others are also broodless, but it does give me some confidence that I’d chosen the correct weather to treat.

† This article, like most on this site, discuss beekeeping issues relevant to temperate climates. It’s important to make this clear now as most of what follows is irrelevant to readers from warmer regions.

∞ Even if there is brood in midwinter, it’s going to be in pretty small amounts. The rate at which this brood emerges is going to be low. The chances of determining what’s going in the colony by ‘reading the tea leaves’ from the debris falling through the mesh floor of the hive is therefore not great. It would probably also require repeated visits to the apiary.

ß This needs qualifying … in midseason, when the temperature varies but it’s not generally cold, the nectar flow is probably the rate-limiting step for brood rearing. The June gap is regularly associated with the queen shutting up shop for a while. However, in late autumn and early winter I’m sure the plummeting temperatures is a major influence on egg laying by the queen.

‡ National … Ha! Most are only national if you live within the M25. Anywhere else and you’re usually much better off accessing some data from closer to home. It’s worth noting that the sort of ‘amateur’ weather stations I discuss do vary in data quality. For example, they’re a bit dodgy recording temperatures in full sun (they tend to over-read). However, if you find a local one, check the temperature in comparison to a thermometer in your apiary, you’ll find it’s a useful way to monitor what might be happening in the hives.

§ I don’t routinely generate these graphs – I have a life (!) – but did specifically to illustrate this post. It’s sufficient to simply monitor the average temperature.


Whether the weather be fine
Or whether the weather be not,
Whether the weather be cold
Or whether the weather be hot,
We’ll weather the weather
Whatever the weather,
Whether we like it or not.

















Apis mellifera aquaticus

Early June 2017 ...

Early June 2017 …

June in Fife was the wettest year on record. It started in a blaze of glory but very quickly turned exceedingly damp. The photo above was taken on the 7th of June. One of my apiaries is in the trees at the back of the picture. Six queens emerged on the 2nd or 3rd of June to be faced with a week-long deluge. The picture was taken on the first dry morning … by the afternoon it was raining again, so delaying their ability to get out and mate (hence prompting the recent post).

And so it continued …

Early July 2017 ...

Early July 2017 …

Here’s the same view on the 1st of July. Almost unchanged … ankle deep water en route to the apiary, the burn in flood and some splits and nucs now being fed fondant to prevent them starving.

A beautiful morning though 😉

Retrospective weather reports

Of course, you shouldn’t really worry about weather that’s been and gone, though comparisons year on year can be interesting. At the very least, knowing that the June monthly rainfall in Eastern Scotland was 223% of the 1961-99 average, I’ll have an excuse why queens took so long to mate and why the June gap was more pronounced than usual. Global warming means summers are getting wetter anyway, but even if you make the comparison with the more recent 1981-2010 average we still got 206% of the June monthly total.

The Met Office publishes retrospective summaries nationally and by region. These include time series graphs of rainfall and temperature since 1910 showing how the climate is getting warmer and wetter. If you prefer, you can also view the data projected on a map, showing the marked discrepancies between the regions.

June 2017 rainfall anomaly from 1981-2010

June 2017 rainfall anomaly cf. 1981-2010 …

Parts of the Midlands and Lewis and Harris were drier than the June long-term average, but Northern England and Central, Southern and Eastern Scotland were very much wetter.

It would be interesting to compare the year-by-year climate changes with the annual cycle of forage plants used by bees. Natural forage, rather than OSR where there is strain variation of flowering time, would be the things to record. As I write this (first week of July) the lime is flowering well and the bees are hammering it. The rosebay willow herb has just started.

Rosebay willow herb

Rosebay willow herb

Prospective weather forecasts

Bees are influenced by the weather and so is beekeeping. If the forecast is for lousy weather for a fortnight it might be a good idea to postpone queen rearing and to check colonies have sufficient stores. If rain is forecast all day Saturday then inspections might have to be postponed until Sunday.

If you have a bee shed you can inspect when it’s raining. The bees tolerate the hive being opened much better than if it were out in the open. Obviously, all the bees will be in residence, but their temper is usually better. They exit the shed through the window vents and rapidly re-enter the hive through the entrance.

I don’t think there’s much to choose between the various online weather forecast sites in terms of accuracy, particularly for predictions over 3+ days. They’re all as good or as bad as each other. I cautiously use the BBC site, largely because they have an easy-to-read app for my phone.

Do I need an umbrella?

For shorter-term predictions (hours rather than days) I’ve been using Dark Sky. This can usefully – and reasonably accurately – predict that it will start raining in 30 minutes and continue for an hour, after which it will be dry until 6pm.

The forecast in your area might be different 😉

Dark Sky via web browser

Dark Sky via web browser

There’s a well designed app for iOS and Android as well that has neat graphics showing just how wet you’re likely to get, how long the rain will last and which direction the clouds will come from.

Dark Sky on iOS

Dark Sky on iOS

It’s far from perfect, but it’s reasonably good. It might make the difference between getting to the apiary as the rain starts as opposed to having a nice cuppa and then setting off in an hour or two.

Rain stopped play

I’ve posted recently on delays to queen mating caused by the poor weather in June. I’ve now completed inspections of all the splits. Despite both keeping calm and having patience I was disappointed to discover that the last two checked had developed laying workers. Clearly the queen was either lost on her mating flight or – more likely (see the pictures above) – drowned.

I’ve previously posted how I deal with laying workers – I shake the colony out and allow those that can fly to return to a new hive on the original site containing a single frame of eggs and open brood. If they start to draw queen cells in 2-3 days I reckon the colony is saveable and either let them get on with it, or otherwise somehow make them queenright.

One of the laying worker colonies behaved in a textbook manner. A couple of days after shaking them out there were queen cells present. I knocked these back and united the with a spare nuc colony containing a laying queen.

Lime can yield well in July

Lime can yield well in July

The second colony behaved very strangely. I didn’t manage to inspect them until a week after shaking them out. There were no queen cells. Nor was there any evidence of laying worker activity in the frames of drawn comb I’d provided them with. Instead, they’d filled the brood box with nectar from the nearby lime trees. Weird. I united them with a queenright colony and I’ll check how they progress over the next week or two.

Apis mellifera aquaticus

My colonies are usually headed by dark local mongrel queens. My queen rearing records show that some are descended from native black bees (Apis mellifera mellifera) from islands off the West coast of Scotland, albeit several generations ago. These bees are renowned for their hardiness, ability to forage in poor weather and general suitability to the climate of Scotland.

Nevertheless, without further natural selection and evolution they will have still needed water wings, a snorkel and flippers to get mated last month 😉

Not waving but drowning


Carl Linnaeus

Carl Linnaeus

The taxonomic scheme ‘developed’ by Carl Linnaeus (1707 – 1778) is a rank-based classification approach actually dates back to Plato. In it, organisms are divided into kingdoms (Animals), classes (Insecta), order (Hymenoptera), family (Hymenoptera), genera (Apis) and species (mellifera).

The subspecies is indicated by a further name appended to the end of the species name e.g. Apis mellifera capensis (Cape Honey bees), Apis mellifera mellifera (Black bees)

Apis mellifera aquaticus doesn’t really exist, but might evolve if it remains this wet 😉

Was it good for you?

Her majesty ...

Her majesty …

Queen development takes just 16 days:

  • she hatches from the egg on day 3
  • the cell is capped on day 7
  • the virgin queen emerges on day 16

There’s then a further 6-7 days until she becomes fertile and goes on her mating flight(s). These are weather dependent, needing warm, calm and sunny conditions, usually between 2pm and 5pm. These can often be relied on in late May and June, but are a bit more hit and miss late in the season. Fortuitously for a small number of queens in my apiaries it looks like they’ll be enjoying great conditions for their nuptials … yesterday or today.

Near-perfect ...

Near-perfect …

I’ll check in a week or so and hope to find mated laying queens …

Queen clipping – why?

I sometimes have colonies in my (very) small suburban garden … it’s great to be able to watch the bees before leaving for the lab or to observe them early in the season bringing in pollen from the crocuses. It’s also a convenient staging post between my out apiaries and a whole lot easier than carrying heavy boxes around through waist-high field margins. However, I’m aware that my neighbours may not share my enthusiasm for bees. I therefore do my utmost to only keep well-behaved colonies in the garden by selecting for docility as a priority when queen rearing. In addition, I make sure any queens heading colonies in the garden are clipped. Queen clipping is the trimming of one wing, preventing the queen from flying any distance should the colony swarm. In the absence of a queen, a prime swarm leaving the hive will either return to the hive or will cluster with the queen a very short distance from the hive.

Clipped queen ...

Clipped queen …

A colony in the garden swarmed on open queen cells (QC) last Sunday afternoon. The colony had chosen to ignore the super, so filled the brood box with nectar (I suspect I’d added the super too late and the colony had already started to think about swarming). Consequently the colony ran out of space. The QC’s were about 3-4 days old and unsealed. There’d been none present at the previous inspection (remember that colonies usually swarm once the first QC’s are sealed). The colony was half-way through a vertical split (to be described in the future) with the original queen in the top box and the newly emerged virgin in the bottom box. I’d been away and arrived home to find the top box swarming and the air filled with bees. With an unclipped queen they would usually settle in a nearby tree or bush and then send out scouts to find more desirable accommodation.

I might have been fortunate enough to catch this, but they might have settled somewhere inconvenient like the chimney or on the kids trampoline in the garden next door. However, because the queen was clipped, she couldn’t fly and the bees just milled about for 15 minutes … a fantastic sight and sound. Eventually they returned to the hive … but to the bottom box. Shortly after they’d settled I found the queen and a small retinue of workers on the ground about a metre from the hive entrance (see photo above). I quickly went through the top box, shaking bees off the frames and knocked off all the QC’s. I also swapped out a couple of nectar-filled frames for drawn comb. I then ran the queen back into the entrance. With luck the reduced density of bees and increased space to lay will discourage them from swarming again*.

A queen with a clipped wing generally swarms later than an unclipped queen, potentially giving you a few extra days between inspections. However, as the example above shows, you can’t rely on this so seven day intervals between inspections are still recommended. Had I not found the queen she would have probably crawled back to the hive stand, climbed up the leg and ended up under the open mesh floor. Although this is not ideal, it provides another opportunity to recapture her and it’s far preferable to losing the bees altogether or bothering your neighbours with swarms.

Summer storm ...

Summer storm …

Although the weather was wonderful when the colony swarmed, it rapidly changed later in the afternoon when we were treated to downpour of biblical proportions … any swarm caught out in the torrential rain and hail would have probably fared very badly.

Time to close the hive up ...

Time to close the hive up …

The image above (the densest cloud formed a wide band from the North East to the South West, almost directly above three of my apiaries) is a composite of three images stitched together in Photoshop. I was desperately trying to get through the last few hive inspections but had to abandon things and seek shelter in the car. The rain and hail didn’t last long, but what it lacked in duration it more than compensated for in volume (both sound and fluid ounces).

Perhaps surprisingly, in the 30 minutes or so before the heavens opened the bees were remarkably well behaved.

* Update on checking six days later (today) the blue marked and clipped queen is back and laying again in the top box. It looks like she’s been getting a lot of attention as the blue paint has almost disappeared. There are no signs of any more queen cells but they’re still not taking much notice of the super. Unfortunately, they are showing signs of robbing another colony in the garden, so I’ll shortly be moving them to another apiary.

In the meantime, I prepared a stack of boxes in preparation of moving house and – within 24 hours – another swarm moved in. I’d missed a finger-wide gap in the stack and the bees occupied a chest-high pile of broods and supers. These look like another generous donation from a neighbour … thank you.

Going over

Two images from the last week showing the oilseed rape (OSR) going over. The first – from the last day of May – nicely sums up the weather we’ve enjoyed this Spring. The OSR is already fading fast.

Mainly dry ...

Mainly dry …

The excellent Bablake School weather station recorded May 2015 as having more rain, less sunshine and colder temperatures than the 30 year average for Coventry. The average maximum temperature was 15.2ºC (1.4ºC lower than average) explaining the slow build-up of colonies. The OSR was in full flower before most colonies were able to fully exploit it and even strong colonies were hampered from foraging by the weather.

Yellow path ...

Yellow path …

And a week later (7th June) it’s gone. Typically, colonies that have been foraging on OSR get bad tempered once flowering is over. It’ll be interesting to see whether this happens this year when they’ve hardly had the opportunity to use the OSR. In the photo above it’s not clear why the only OSR flowering is along the footpath … I suspect these were slightly lower growing plants which were a bit more sheltered. Some of the sheltered field margins also had flowers lingering. However, there were almost no bees on the flowers and it’s effectively over for the year.