Contact killer – The Apiarist

As the times get shorter and the beekeeping season turns into only a fading (blissful) reminiscence, customer numbers to this website begin to dwindle. Nonetheless wholesome , however maybe solely 30% of the numbers in Might and June.

That is partly as a result of there appears to be much less to do right now of the season.

No swarming, no queen rearing, no honey to reap … and for a lot of, no actual ideas of beekeeping.

It’s additionally undoubtedly as a result of the voracious ‘learn all you possibly can’ newbies now have a number of months beekeeping expertise.

Some are prone to suppose they know all of it already .

Others might have given up in disgust when their colony swarmed (once more) in August and so they ended the season dispirited, queenless and honey-less 🙁

After all, some beekeepers shall be conscious that, though there are some winter (or late autumn) duties, there isn’t a rush … there’s an entire winter forward to cope with these and the whole lot ought to then be nice till the season begins.

Au contraire as we used to say earlier than Brexit 🙁

The paradox of timing miticide remedies

There stays one critically ‘time delicate’ activity to finish earlier than the bees are prepared for the season forward.

Or, as I shall present shortly, not time delicate with regard to the calendar, however time delicate with regard to the state of the colony.

Not feeding … that ought to already be full and they need to not want topping up (if in any respect) till brood rearing actually begins to ramp up within the early spring.

What must be achieved is to kill the mites – or as many as you possibly can of them – that survive after the late summer time/early autumn miticide remedy.

There’s an fascinating paradox in miticide remedy …

The earlier you deal with for mites as soon as the summer time honey has been eliminated, the extra mites are current within the hive on the finish of the calendar 12 months. If you concentrate on this – or take a look at my crudely drawn diagram – it needs to be apparent why that is:

Mite numbers on the finish of the 12 months and the affect of early remedy

Should you deal with early sufficient (crimson line) to guard the winter bees from the ravages of Varroa and viruses, the mites that survive remedy will proceed to breed within the small quantity of brood reared on the finish of the season (crimson arrow).

In distinction, in the event you deal with too late to guard the winter bees (blue line), the surviving mites can have nowhere to breed as brood rearing can have stopped (blue arrow).

And there will be surviving mites.

Not one of the permitted miticides will kill greater than 95% of mites within the hive .

Survivors

So, to start out subsequent season with the minimal mite load, you actually need to kill as many of those surviving mites as attainable.

The standard selection for a ‘midwinter’ mite remedy is oxalic acid. This may be trickled or vaporised and, below optimum circumstances, kills 90-95% of the mites. You solely must administer it as soon as and it’s fairly effectively tolerated by the bees

Let’s assume there are 200 mites remaining in your colony after the late summer time miticide remedy and the final little flurry of mite hanky panky copy within the ultimate spherical or two of brood reared by the colony.

Should you can kill 90% of those mites with a single OA remedy there’ll solely be 20 mites remaining originally of the next season.

However are you able to kill 90% of them?

Oxalic acid is just efficient towards phoretic mites. Any mites lurking in capped brood cells will escape remedy. Subsequently, if some, most or all of these 200 mites are in capped cells there shall be considerably extra remaining in the beginning of the next season.

Through the energetic brood rearing season it has been decided that ~10% of mites are phoretic at anyone time. Sadly, I’m not conscious of any comparable research for the proportion of mites which are phoretic exterior the spring and summer time.

So, within the absence of any onerous information let’s do some arbitrary arm waving calculations … 😉

The graph beneath reveals the numbers of mites surviving a 90% oxalic acid remedy the place the proportion of phoretic mites ranges from 100% to 10% i.e. a spread protecting the whole lot from a completely broodless colony to 1 with extra brood in all phases for the mites to parasitise.

Whole mite numbers surviving OA remedy relies upon upon the proportion which are phoretic when handled

Unremarkably … the better the proportion of mites which are phoretic, the less mites are left within the hive after the oxalic acid remedy.

And, equally unremarkably, for a contract contact killer like oxalic acid, it’s only when all of the mites are phoretic that 90% of the unique 200 mites could be killed. As you possibly can see from the graph, if solely 50% of the mites are phoretic, 55% of the whole variety of mites within the hive will survive remedy.

Should you take a look at the ten% phoretic column you’ll perceive why a single oxalic acid remedy within the peak of the season – or for that matter dusting with icing sugar (which is even much less efficient) – has solely a really restricted influence on the general mite numbers. If solely 10% of the mites are phoretic then a whopping 91% of the mites (182) will survive.

Whopping?

Aren’t these are all fairly small numbers?

20, 74, 146?

What’s a handful of mites between associates?

Does it actually make a distinction whether or not your hive accommodates 20 or 74 or 146 mites originally of the next season?

Sure, it does.

It makes an monumental distinction.

The mites current in early January will reproduce as brood rearing ramps up in spring. Subsequently, at any specific time level within the season – assuming all different issues are equal – there shall be a considerably increased mite load in a colony that began the 12 months with extra mites, than one which began the 12 months with fewer mites.

We all know fairly a bit concerning the copy of Varroa. For instance, we all know extra progeny are reared when feasting on drone slightly than employee pupae (due to the longer period of pupation). There are a bunch of extra parameters that affect the copy charge of the mite inhabitants – the proportions of drone to employee brood, the supply of brood, the period of the phoretic section of the life cycle (in flip, probably influenced by the supply of suitably aged nurse bees) and so forth …

All of which signifies that we will predict the variety of mites current in a hive in the course of the season primarily based upon the variety of mites in the beginning if we make a collection of assumptions of hive power, time of the season, charge of colony construct up and so on.

I used to make use of the BEEHAVE software program to do this sort of colony modelling. Nevertheless, current modifications to the programming language ) means BEEHAVE now barfs a slew of error messages again at me once I use it. Since I’m not eager to try to patch up one thing that’s primarily based on outdated or deprecated libraries I’ve as an alternative been dabbling with Randy Oliver’s Varroa Mannequin which is Excel-based.

Randy Oliver’s Varroa Mannequin

A lot of you’ll know Randy as a daily contributor to the American Bee Journal, a industrial beekeeper and the creator of scientificbeekeeping.com.

Modelling mite numbers

Utilizing this mite calculator you possibly can simply predict how mite ranges construct up over the season.

Assuming there was an extra of brood accessible all through the season (there isn’t as I shall clarify shortly) you may count on mite numbers to extend 154-fold between January and September.

Unrestricted mite replication – the extra you begin with the (many) extra you get

Subsequently, in the event you began the season with simply 20 mites there could be ~3000 within the hive by the point the colony is rearing the winter brood in September.

Conversely, 182 mites in January would multiply to over 28,000 by September 🙁

After all, there may be not an extra of brood accessible all through the season. For instance, within the early spring brood is limiting. Nevertheless, we will issue brood availability by modifying the calculations to take account of colony power and construct up, reinfestation charges and the proportion of drone brood being reared within the hive.

All of which has conveniently been included within the Varroa Mannequin … thanks Randy 🙂

Mite numbers in September predicted with Randy’s Varroa Mannequin

These varied limitations inevitably prohibit mite copy and the fold-increase between January and September is ‘solely’ about 100. Which means that a colony that began the season with 20 mites will comprise simply over 2,000 by September, whereas a colony that began with 182 mites will find yourself with over 18,000 by the top of the summer time.

18,000 is so much lower than 28,000 … however it’s nonetheless a humungous variety of mites.

Or, extra scientifically, it’s an infestation stage that the colony is unlikely to outlive. 18,000 mites might be effectively over one mite for each two grownup bees within the colony. With that stage of mites you possibly can count on each pupa to be parasitised.

The colony is doomed.

You’ll be able to test these numbers if you need. The Varroa mannequin is freely accessible from scientificbeekeeping.com and is effectively documented. I used V19 for the calculations above. I additionally used the mannequin with nearly the entire default settings unchanged – particularly this was the colony kind Randy designates ‘D’ which means Default colony in temperate local weather, managed to forestall swarming (slight fall brood buildup). The one change I made was to set mite immigration (drifting) to 0.

Are you now satisfied of the necessity to deal with in ‘midwinter’?

The ‘midwinter’ mite remedy must be utilized to minimise the mite ranges the colony begins the season with the next 12 months.

Nevertheless, to be maximally efficient, this ‘midwinter’ remedy must be utilized when the entire mites within the colony are phoretic. That signifies that winter oxalic acid trickling (or vaporisation) must be achieved when the colony is broodless.

Not when it’s handy for the beekeeper as a result of s/he’s getting over an extra of mince pies and port within the now nearly common holidays between Christmas and New Yr’s Day.

‘Midwinter’ is not in the midst of winter … beekeepers ought to (mis)use the time period in the identical method they (mis)use phoretic … i.e. not actually.

Brood rearing – if it ever stops (which I’ll return to on the finish) – most likely restarts across the winter solstice. That signifies that there shall be sealed brood within the colony early within the New Yr. I don’t know the way a lot of that brood is prone to be infested, however I do know that any that’s infested will inevitably imply that I’ll be killing fewer mites than I may … and subsequently that I’ll be risking exposing the colony to a lot increased mite ranges later within the season.

We’re now in mid-November. Virtually all beekeepers ought to have accomplished their late summer time miticide remedy by now. My Apivar strips had been eliminated nearly a month in the past.

The exact timing of the ‘midwinter’ mite remedy is irrelevant so long as it coincides with a broodless interval within the colony.

I subsequently monitor brood manufacturing in my colony from late October onwards. As quickly because the colonies are broodless I deal with with oxalic acid.

There may be nothing to be gained by ready till later within the 12 months. A phoretic mite is a phoretic mite … as soon as they’re unable to cover away I’ve obtained a 95% probability of killing them.

These are my kind of odds 😉

I’ve beforehand mentioned learn how to monitor for a broodless interval. Should you don’t need to open the hive then learn to learn the particles on a Varroa tray. It’s not witchcraft or rocket science.

Biscuit colored (or a bit darker) cappings indicating brood rearing on this colony

I count on my colonies to be broodless subsequent week. It’s a bit later than final season, however we had heat climate by way of a lot of the early autumn. In the event that they’re not broodless but I’ll maintain off remedy for a fortnight or so. Previous expertise has taught me that the colonies (right here in Scotland) are nearly inevitably broodless for no less than 2-3 weeks between late October and mid-December.

And, in case your colonies are by no means broodless within the winter, the entire above nonetheless applies … besides you’ve got the marginally tougher activity of figuring out when there may be the minimal stage of sealed brood within the colony.

Why the minimal stage?

As a result of, until there are bizarre issues like a number of mites infesting every cell, it’s logical to imagine that when the brood stage is at a minimal the phoretic mite stage shall be at a most.

International warming

As we attain the top of a not-altogether-convincing COP26 convention I assumed I’d additionally point out a current paper by Giles Budge and colleagues in Newcastle.

I’ve discovered it’s simpler to handle mite infestation ranges in Scotland than once I lived within the Midlands. I’ve much more flexibility within the timing of the winter remedy now because the colonies are broodless for longer.

With world warming we will count on hotter winters and subsequently it’s possible that colonies might have sealed brood for extra of the calendar 12 months.

That can make mite administration tougher.

Actually not not possible although … notably in the event you be taught now 😉

Notes

A serious energy outage has meant this was written by candlelight and hot-spotted cell phone connection. As soon as energy is restored I’ll return and tidy among the textual content and add the key phrases. Within the meantime I’ll hearth up my trusty Ghillie kettle to make one other brew 😉

Ghillie kettle