Winter Feeding and Mite Teatment

Through winter the bees are all busy keeping warm, clustered in their hives away from the prying eyes of beekeepers. Barring a bit of hardware maintenance, woodwork and renewing Beekeeping Association subs there isn't much for Beekeepers to be doing. However there are two bee related tasks still to be done: mite treatment and Winter feeding.


The mite treatment as with every other year is an organic acid treatment which kills off a huge proportion of the varroa mites in the hive. There's a couple of options but most beekeepers seem to be using an Oxalic Acid solution. It's easy to make, just dissolve 35g Oxalic Acid Dihydrate in one litre of sugar syrup -most sources say to use 1:1 syrup but 2:1 syrup has been used by some. The hive is then opened and the syrup trickled between the frames directly onto the bees. As the bees move about the solution gets distributed over the whole colony and onto the mites. It takes 5ml per seam for a National hive and by my calculations 6.6ml per seam for a Commercial. It's only effective when the mites are actually on the bees though so needs to be done then the colony is broodless. If there's brood most of the mites will be in the comb with new larvae and the oxalic solution won't reach them. Waiting for a long enough cold snap took a while but I treated my colonies about a fortnight ago.

Mite treating time

Oxalic solution is very cheap and easy to make at home, unfortunately it's no longer legal for beekeepers to do so. Last year a firm called Api-Bioxal registered it as medical product so now any treatment with Oxalic Acid needs approval from the Vetinary Medicines Directorate. This means you can't just whip up your own solution or buy it from just anyone anymore, you need to buy the approved and expensive VMD approved product. The approved Api-Bioxal currently costs £10.99 for a 35g  sachet of what is clearly Oxalic Acid Dihydrate, if you shop around and source your own >99.5% pure Oxalic Dihydrate you get about half a kilo for that price. So the cost of treating my 8 hives with Api-Bioxal comes to about ninety quid whereas using other Oxalic Dihydrate I'd be paying under a fiver. Not that I'm suggesting anyone does ..obviously I used the super expensive pricey approved stuff and the photo above shows a bottle of lemon barley water I was drinking at the time and the syringes were just so I could drink it through the veil of my beekeeping jacket. Honest.

Can see the roughly round shape of the cluster here.

I've not seen my bees for a long time, what with it being winter and all but opening hives in Winter is quite different to Summer. In the summer bees tend to be distributed allover the comb in the brood box but in winter they form a rounded cluster and when you remove the crownboard you can clearly see the shape of it. All being well the cluster moves in the hive using stored food from the combs.

When I was doing the treatment I found four of my colonies are still very densely populated with huge clusters whereas two are like the one above where there's been some of the expected die back and two are looking very low on numbers. The two colonies that are low on numbers may struggle to generate enough heat so I whilst I've  so far left the mesh floors open with those two I closed them to try an conserve heat -I very much doubt they'll make it through Spring but shall wait and see.

You can order anything, as long as it's sugar.

In Winter hives can be running a little low on stores -especially big strong colonies that haven't experienced much die back  through Winter. Because of that it's fairly common practice to give the colonies a little food top up. Bees won't take syrup when it's cold so instead the beekeeper can give them dry sugar or fondant. In previous years I've made candy boards which are effectively huge square sugar lumps covering the top of the hive so the bees have access to emergency food wherever they are in the colony. I had planned to make newer shallower candy boards but never got round to it so this year I've gone back to fondant again.

Fondant can be given in a block, as it comes from the packet, placed above the feed hole in a crownboard with a plastic food tub above it which I've done previously. This time I decided to just cut the Dr Oetker Ready to Roll Icing very thinly and place it above the frames in the small gap between the frame tops and the crownboards. With the fondant in place the crownboards, insulation and roofs were quickly put back in place so the bees could get back to warming the air in there.

Bees making cleansing flights, must be quite a relief for them.

On Monday just gone I popped to the out apiary and was able to see bees making cleansing flights although according to my weather app it was only 7 degrees Celsius. It's been a fairly warm winter so far, which isn't great for the bees. In a cold winter they're less active and cluster tighter using less food, when it's warmer they're more active which means using up more energy and depleting food stores faster. In early Spring I'll need to check how much they've got left as that's the time they're at most risk from starving.

Winter mite treatment

There isn't a lot for beekeepers to do in the winter except maybe drink mead, argue on forums, pad out their blogs with book reviews and clean equipment for next year but one winter activity that needs doing is the mite treatment. As with every other winter whilst there's no brood in the comb the varroa mites will be clinging to the bees which makes them vulnerable.

Can't see any mites, but they'll be in there somewhere..

The treatment we use is a solution of organic acid and sugar syrup. Lactic, Formic or Oxalic acid is used with the latter being the most popular going by the forums and articles posted. I gather there's been a recent change in the legal status of Oxalic Acid to treat mites so it's now comes under the control of the Vetinary Medicines Directorate and is considered an Annex II product whatever that means (seriously I don't have a clue). The upshot is it needs to be prescribed by a vet, however it's still being sold as a hive cleaning product so beekeepers can still get hold of it. So er yeah I'm actually applying Oxalic Acid to clean the hive, specifically the hive floor between the frames. If it goes on some bees that happen to be in the way and happens kills a 90% of the mites well that can't be helped :)

The Oxalic acid solution isn't actually that wonderful for the bees but it's 70 times more damaging to the mites. There's different recommendations of the strength of solution to use and a lot of studies have been done on the balancing act between minimising it's effect on the bees and maximising it's the impact on the mites. 3.2% is the strength of solution sold by people like Fragile Planet and Thorne. Confusingly there's two different ways to measure it there's the % concentration or the % by weight of crystals to syrup solution .

Do not eat.

Previously I've bought ready mixed Oxalic acid solutions but this year I decided to save a little coin and mix my own, so I bought half a kilo of Oxalic Acid Dihydrate Crystals. It's very cheap stuff. The recipe I followed was from Montgomery Beekeepers Association website 1KG of sugar dissolved in 630ml or water, I then decanted a litre into a jug and added 35g of Oxalic Acid Dihydrate crystal. I didn't need a litre of the stuff but as the article notes the more solution you make the lower the error margin when you add the oxalic crystals.

Add caption

The amount given to use if 5ml per seam which is based on a National Hive brood box, I use slightly bigger Commercial brood boxes so I aim for 6ml of solution per seam.

We've had some really cold days and nights recently but even though it was 22nd December the weather had warmed to 14.5 degrees Celsius so the bees were flying. I started with Hive4 which I'd thought had a small population but there were 9 seams of bees to treat so they're more populous than I expected. They were very placid and I was able to treat them without a problem.

Hive3, the brief calm before the storm.

Hive3 is my aggressive colony. I'd thought with they might've calmed down a little having requeened them a few months ago, left them alone save for feeding and it being December. They hadn't. They'd done an excellent job of gluing the crownboard to the frame tops so it took me a long time to prise it off, once the hive was open it wasn't long before they were on the attack. After a few puffs on the smoker I quickly administered one syringe worth of solution and was rewarded with a sting on the wrist. I decided to walk away and let them calm down before continuing so wandered to the other side of the garden whilst a little contingent of angry bees followed me bouncing of my head. Eventually they subsided after puffing a lot of smoke around me so I returned to the hive, I repeated the process twice to complete their treatment before moving onto Hive1. I'm thinking I should probably have done the aggressive bees last as the amount of alarm pheromone they're probably throwing out may well affect the other colonies. Luckily the bees in Hive1 didn't seem that bothered by my opening them up and trickling acid on them. Hive2 weren't quite so relaxed with one bee stinging my leg and I later found another had crawled up the wrist of my glove.

All finished.

I also added candy boards to each hive, did it at the same time to minimise disruption to the bees but I'll cover that in another post. The excess oxalic solution went down the sink with a lot of water. I'm unsure of it's shelf life but it's cheap to make if you have crystals and the ready made stuff is usually given a fairly close use by date so I wasn't going to mess about trying to store it.

Trickling Acid

Most of a hive's Varroa mite population, well 85% of them, usually live within the developing brood leaving only 15% of the population on the adult bees. When there's no brood all the mites should be on the adult bee population and this makes them vulnerable to treatments applied directly to the bees. The treatment I'll be using is a solution of Oxalic acid and sugar syrup.

For the past six weeks or so the night time temperature over here has mainly been below 5 degree Celsius with a some nights of temperatures below freezing. This should mean that by now the queens have stopped laying eggs and the last of the brood should have hatched by now. With hopefully no brood in the comb the mites should all be rather vulnerable. Obviously if there are brood in the hive then the mites will be safely ensconced in the comb and the acid won't affect them.

Off to work we go

Today was a balmy 9 degrees C, armed with a smoker, hive tool a couple of syringes and a bowl of oxalic acid solution I'd warmed in a water bath I went to meet the bees. They were making the most of the slightly warmer weather and whilst I had expected them to be making cleansing flights but I also noticed they were  bringing in pollen from somewhere too.

Are you ready for your treatment?

Including the space between the end frames and the follower boards there's 12 seams per hive. Hive3 with it's caught swarm had about 4 seams worth of bees and was unsurprisingly the weakest colony. They were also the most edgy with a lot of bees flying out to meet me and inspecting the syringe. Hive1 had eight seams and Hive2 was packed with 12 seams of bees. The guidelines are based on a National brood box and suggest 5ml of solution is dribbled down each seam of bees. As I use a commercial which is a little bigger I did a little guesswork and used about 6-7ml per seam. It's a simple enough procedure, you just open the hive and run a syringe along each seam gently squeezing out the solution as you go. Once completed the hives are closed up and you're done.

Seams of bees

Schrodinger's Bees

Winter is a period when beekeepers don't do a huge amount of hands on beekeeping. It's a good time to clean up kit, drink some mead, pad out your blog with book reviews and so on but as far as contact with the bees go there's not a lot. Whilst beekeepers do their best to ensure their colonies will survive the winter we do seem to end up a with a Schrodinger's Cat sort of situation. Are the bees in the boxes alive or not? There's a lot that can happen to them over the winter. They could starve if they didn't have enough food stored or warm snaps made them use up what they had too quickly, they might get damp and die, varroa load may be too high or some other pest or illness may have wiped them out.

Anyone alive in there? Knock once for yes, twice for no.

I occasionally pull out a stethoscope and have a listen to my colonies just to be sure they're still alive in there. Hopefully the bees have been living on the honey stored in the comb of the brood box, but that may be running low by now so many beekeepers will feed their colonies a nice lump of fondant icing after xmas. Actually I got an email from Fragile Planet last week advising customers to feed their bees this winter. However I'd given mine some fondant back in November just in case it was needed and as I checked recently I was able to see most of it still there, it may be a little dry but condensation inside the hive should provide water to allow the bees to use it.

Lotta sugar and 3 bees. The brown stuff is a supplement.

Another thing beekeepers do when it's cold is pour acid on their insects. Sounds a bit strange, I know, but it's for the benefit of the colony. It's intended to kill the varroa mites. Normally most of the mites will be safely tucked away in the capped brood along with the bee larvae they're feeding on, however when it's too cold to raise larvae the queen stops laying eggs so the mites hang about on the adult bees instead at which point they're more vulnerable to varroacides, specificall organic acids applied to the bees directly. The January edition of the BBKA News advised waiting for a period of cold weather with an average of 5 degrees Celsius, lasting three weeks so any capped brood will have emerged. Then as the cold snap comes to an end you trickle a 3.2% oxalic acid solution and 1:1 syrup onto the bees between the combs. The bees between the combs are called a seam, and the figure people go by is 5ml of solution per comb. I suspect that's actually based upon the population of standard National hive brood box really and it may be that in a Commercial like mine you should use a little more but I decided to go with 5ml per seam for now. I think I read somewhere that the acid damages the mouthparts of the varroa leading to their demise, many believe it also does some harm to the bees but less than the varroa would do and given the short lifespan of individual bees shouldn't be a significant problem for the colony as a whole. The figure bandied about for efficacy of dribbling oxalic acid onto the bees seems to bea reduction of about 90% in the colony's varroa population.

Do not drink me.

A very weak solution of Oxalic Acid is used for this, other organic acids can be used such as Formic or Lactic Acid, but Oxalic is currently in vogue. It's legal status seems a little confusing to me, the choice of these organic acids as varroacides seems to be based upon them not having a defined Maximum Residue Limit like regular pesticides. I gather these organic acids occur naturally to some degree within bee colonies anyway and unlike other varroacides don't leave a residue affecting the hive products. It's not difficult to make up your own solution, but if you get it a bit wrong it could be a disaster for your bees either by not killing enough mites or by damaging the bees themselves -and do you really know how accurate your kitchen scales are? I doubt it.

If you really want to know more about varroa control DEFRA have a 44 page document available called Managing Varroa that you can download and includes Oxalic Acid treatments. There's other ways to administer organic acids such as spraying or vapourising the stuff. Vapourising seems wonderfully dangerous giving beekeepers the chance to find out first hand how much damage of a lungful of vapourised acid can do to a person, whilst simultaneously being less effective on the varroa. The advantage of vapourising it is it's faster to do than dribbling, although that doesn't take into account time spent waiting for an ambulance and further time spent recuperating after burning your lungs out.

Back to my bees. I've never used oxacilic acid before but you administer it by dribbling it from a syringe. It just so happens I'm no stranger to drawing up and administering solutions in syringes, and it's easier without a needle involved.

My table needs a clean

Today the temperature below the hives was 8 1/2 degrees Celcius, the warmest it's been for a few weeks so I decided to apply the acid -it was also due to expire next month too. After lighting the smoker and popping on my smock and veil I decided to treat the bees in the nuc first. As I said above it's hard to know how the bees are doing over winter despite best efforts in the lead up to winter so it was something of a relief when I removed the nuc's crownboard to see bees in there under the fondant and more coming up from the seams to see why some fool was opening their hive in late Janury.

They're alive!

There looked to be four seams full of bees. In the photo you can see three of them, the edge seam on the left was also full of bees but they'ed propolised the top edge so you can't see them so well in the image. The two seams on the right were more or less empty of bees. Interestingly (slightly) the left side of the hive is more exposed with the right side facing Hive1 so I'm assuming they found it easier to keep warm on the left of the hive than the right. I drizzled 5ml of oxalic and syrup solution into each of the four occupied seams making 2 passes for each (2 1/2 ml per pass) rather than drowning them by trying to apply it too quickly. I had some spare brood frames with honey on that I'd stored in the summer in case it was needed in the winter. Rather than disturb the frames the bees were on I prised out the rightmost frame to assess their stores but found it still had capped honey in it, so I guess they're not short of food and that probably explains why they've shown little interest in the fondant so far. Closing up the nuc I cracked open Hive1 where I was greeted by a few bees and saw them crowded into the seams again. I drizzled 5ml of solution into each seam before moving on to Hive2.

"It's January, put the lid back on you muppet!"

In Hive2 I could still see some grey bits of Api-Life Var on the outer corners of the frame tops. This is a crumbly material holding thymol (thyme essential oil) which as it evaporates kills varroa but not bees -although it does annoy them. Normally the bees would have broken it up and thrown it out of the hive by now but with the cold weather I'd guess it's not been evaporating so I pulled them out. There were a few bees on top of the frames and investigating the fondant. Not too many though. If there'd been a lot of them then it would be an indicator that they were starving -I suspect they'ed've eaten the fondant before that was a problem though. Once again I trickled the solution over the bees and closed up. You can see in the above photo the bees are towards the far side of the hive rather than in the middle.That side of the hive whilst nearer the entrance is more sheltered from the elements as it face a garden wall whereas the other side faces the garden. Evidently they've chosen the warmer side of the hive to cluster in. Hive1 had done the same.

Oxalic acid applied and all the hives closed up again I popped to Pearson Park for a quick run. Apart from an occasional check on how much fondant they have left I'll be leaving the bees alone from now till spring.