Vaporising Api-Bioxal

Vaporising Api-Bioxal leaves a burnt caramelised residue in the vaporiser. This is difficult to clean. Does this damage the vaporiser or make it work less efficiently?

Forget it ...

Forget it …

I remortgaged the house, took my kids out of university and cancelled both trips to Mauritius later this year, all so I could afford some Api-Bioxal (a snip at £10.99 for 35g from Thorne’s). Api-Bioxal is the VMD-approved oxalic acid-containing miticide. Only ‘containing’ as – according to the manufacturers instructions – only 88.9% of the dodgy-looking white crystalline powder is actually oxalic acid (OA). The remaining ~11% is a mixture of glucose and powdered silica (VMD documentation [MS Word]) . As cutting agents go, these are relatively harmless. Nevertheless, some have expressed concern that the presence of glucose might leave a horrible gunky mess (a widely accepted technical term) in the bottom of the vaporiser. Let’s see …

Since I’d promised to help a friend with vaporising a few hives that were disappointingly Varroa-riddled when treated earlier in the winter, this seemed a good opportunity to do a side-by-side comparison of Api-Bioxal and OA vaporisation – in terms of residues, not efficacy¹. My vaporiser is an ‘active’ model (made by Sublimox) in which the vaporised oxalic acid is forced out through a small nozzle in about 20-30 seconds (see video). In use, the OA crystals are dropped into a preheated pan – by inverting the Sublimox – so the temperature change from ambient to 157ºC happens more or less instantaneously. Any comments below therefore might not apply to the passive vaporisers like the “Varrox”, or the plethora of home-grown ones² on the forums or variants listed on eBay. In the majority of these types the powder is added to a pan which is then heated to the sublimation temperature³.

At the start of the trial the pan of the Sublimox was clean, contained no residues and was only slightly tarnished (from historical use). This machine has been used dozens of times previously and in each case has been washed out with clean water after use as instructed by the manufacturers.

After a single colony was treated with 1.6g of Api-Bioxal the pan of the Sublimox contained an obvious charred residue.

Single use ...

Single use …

We treated one further hive with Api-Bioxal and took another photograph of the vaporiser ‘pan’ which now contained an even more obvious charred caramelised deposit, bubbled and lumpy in places. This wasn’t a loose flaky deposit, it was burnt onto the base and lower sidewalls of the vaporiser ‘pan’.

Two treatments ...

Two treatments …

In use the ‘collar’ around the plastic (delrin?) cups used to deliver the OA/Api-Bioxal usually have slight traces of the powder left around them. These were particularly obvious when using Api-Bioxal though I’m not sure any greater amount of powder was left here … it just looked a lot worse. It was also more difficult to clean off than ‘pure’ OA.

Plastic cup ...

Plastic cup …

The caramelised charred residues remaining in the vaporiser after two Api-Bioxal treatments needed a combination of scraping with a knife and repeated rinsing with boiling water to remove it. This took several minutes and would clearly be impractical (and irritating) to do between treatments, meaning that the residues would build up quickly over time. Compare the first and second image in the series above to see how much residue builds up at each use (and see the note below regarding the amount vaporised).

Cleaned vaporiser ...

Cleaned vaporiser …

I then added 1.6g of standard oxalic acid dihydrate (Thorne’s) and vaporised it before immediately photographing the unwashed pan and cup. The photo below should therefore be compared directly with the first in this series. You can see the traces of OA powder at the end of the nozzle of the vaporiser, but the pan is completely clean and contains no additional charred and caramelised residues. This vaporisation was done ‘in the open’ (i.e. not into a hive) and it was interesting to see how long it took the extensive cloud of crystals – perhaps 5 x 2 x 2m in extent – to dissipate as it gently drifted away downwind.

Single OA use ...

Single OA use …

But it gets worse …

I actually used much less Api-Bioxal per hive than the manufacturers recommended 2.3g per colony (this is partly because there is published evidence that ~1.4g is sufficient and double that amount provides no increase in mite killing). I didn’t weigh the Api-Bioxal but used one measuring scoop that – from previous tests – is known to contain ~1.6g of OA when full. Had I used the full recommended dose of Api-Bioxal I would have therefore expected the residue build up to be about 50% worse than shown above. On a vaguely brighter note, the powdered Api-Bioxal pours easily and smoothly, presumably because of the anti-caking agents it contains.

What are the implications of this?

I am very disappointed with the amount of residues left in the vaporiser after using even a single (less than recommended) dose of Api-Bioxal. I’m also disappointed with how difficult these are to clean out of the vaporiser. Might these residues damage the vaporiser, for example by blocking the nozzle, or reduce the effectiveness of vaporisation, for example by not allowing the pan to heat as evenly or quickly? I think both of these are a distinct possibility. An advantage of vaporisation is the ease and speed with which OA can be administered. If the vaporiser needs to be cleaned between every (or even every few) hives it would significantly reduce the attractiveness of this type of Varroa treatment. Remember, if you take your PPE seriously – which you should when vaporising oxalic acid – you’ll be wearing gloves, a respirator/mask and goggles throughout this entire procedure, including cleaning out the residues from the hot vaporiser.

No thanks.


Update … 22/2/16

Chris Strudwick kindly sent me before and after photographs of a Bioenoxal vaporiser that had been used once with Api-Bioxal. The ‘before’ image (left) shows the machine after vaporising 1.6g of Api-Bioxal. The ‘after’ shows the “result of 5 minutes with a nylon pan scourer and water after an initial scraping with a hive tool” … so the gunk can be cleaned off, but it takes time.

Many thanks Chris

¹This would have entailed treating hives with a known Varroa-load with either Api-Bioxal or OA. This was not done.

²Some of the DIY vaporisers are either spectacularly dangerous or have been designed without an appreciation of the temperature control required to vaporise oxalic acid.

³If you have a “Varrox”-type vaporiser I’d be interested to hear your experience with using Api-Bioxal.

12 thoughts on “Vaporising Api-Bioxal

  1. Neil

    I was a little surprised when I read that you’d used Api-Bioxal in your vaporizer but before writing this I spotted a flier that came with the BBKA news, I think, saying that there are indeed two methods of use: trickle and vaporisation! Having glucose in the mix is bound to leave deposits unless the temperature is raised very high. I have a Varrox and will stick to OA dehydrate crystals, getting the cost benefit and avoiding the problems that you have found.
    I enjoy reading your blog, keep posting 🙂

    1. David Post author

      Hi Neil
      Api-Bioxal is approved by the VMD for both trickling and vaporisation. I favour the latter method for reasons I’ve presented before. I see no reason why using Api-Bioxal in a Varrox-type won’t also produce a (similar) mess … if you decide to try I’d be interested in hearing how you got on. It might even be worse as the machine heats up more slowly, who knows? But at least there’s no nozzle to potentially block.
      Pleased you enjoy the posts …

  2. David Brazendale

    The *HUMAN* medical profession is required to prescribe using the generic name rather than the trade mark name.

    So beekeepers should also be using the generic material.

    Powdered silica used as an anti-caking agent – I have no objection to that, think back to Secondary School Science (Chemistry in particular), we heated many compound in crucibles made of silica, so its relatively inert.

    Burn any mono-saccharide or di-saccharide or even many carbohydrates and you inevitably get a burnt horrible mess of caramel and/or carbon.

    Also 500g of the generic costs £6.67 plus postage and packing so thats 312 1.6 gram doses at ~2.7p each hive compared with 21 doses of the trade marked item at ~52p each.

    So use the generic every time !!!

    1. David Post author

      I’ve commented on the cost of miticides in general and Api-Bioxal specifically in an earlier post. It’s certainly a lot more expensive than oxalic acid dihydrate (which you can get a lot more cheaply than the figures you quote – see my brief comment on cleaning your yacht). However, it’s significantly less expensive than any other of the leading miticides per treatment. This has to be a good thing.

      Why have they added glucose to the mix? For trickling you add Api-Bioxal to syrup, so it’s nothing to do with that. The cynic in me wonders whether it’s some sort of already-approved additive that’s safe for bees that makes the product distinct from oxalic acid dihydrate.

      How safe is powdered vaporised silica? It’s certainly inert, but there are regulations regarding exposure via inhalation as it’s associated with lung diseases … such as silicosis.

    2. Emily

      Isn’t the catch with using generic oxalic acid that it’s officially illegal here now, so in theory beekeepers could get in trouble if it was found out they’d used it?

      1. David Post author

        Hi Emily … the legality or otherwise of generic OA isn’t really the point. I’m not recommending that beekeepers break the law. However, the licensed product – in my view – does not seem to be suitable for vaporising despite the fact that approval by the VMD has been granted for this mode of delivery. This has been widely discussed on the forums when it became apparent that the product contains sugars. What is the sugar there for? We now have access to an approved relatively inexpensive (in comparison to other miticides) treatment that appears unsuited to one of the recommended, and approved, routes of administration. When vaporised it’s also – again in my view, though the pictures above make it clear – less good than the generic product beekeepers have been using for years. All these comments relate to ease of administration and the residues left after use, not comparative efficacy. I’ve not done this. I have no reason to think it would be any worse, but also no expectation that it will be any better. However, it’s only effective if it is administered and if it makes a mess and is difficult to clean it’s less likely to be used … ironic really when you consider the recent paper from the LASI/Ratnieks group saying OA is best administered by vaporisation!

        1. Emily

          I agree, it seems like a ridiculous situation that the scientific research is telling us vaporisation is best, yet now the only legally approved treatment produces inferior results in vaporisers! It’s obvious that anyone with a vaporiser would be better off using generic oxalic acid, so only authorising Api-Bioxal is a backward step.

          1. David Post author

            In fairness, and to be painfully pedantic (just in case there are any lawyers reading this 😉 ), I don’t think there’s evidence that Api-Bioxal produces inferior results to generic oxalic acid when vaporised. The active ingredient is, after all, exactly the same. What Api-Bioxal does, at least in my machine, is leave a horrible gunky residue that is difficult to clean and that I fear might damage the vaporiser. I think this makes it much less useful and possibly an inferior product.

  3. Chris

    What annoys me is that other beekeepers in the EU are able to use the generic form of OA (not to mention formic and lactic acids) although I understand there has been a recent hitch in some countries with OA being taken off the EU’s ‘positive list’. Generic formic acid however remains freely available. If the restriction on OA and FA is truly driven by European regulatory requirements, how is it the British beekeepers seem to be the only ones without access?

    I use a Bienoxal evaporator. Api-bioxal leaves the same crud as you describe, while pure OA leaves little behind.

    1. David Post author

      Hi Chris
      Do you have any photos of the mess that remains after using your Bienoxal (which, I believe is a passive Varrox-like vaporiser?). If so, I’d be interested in seeing them. It’s disappointing that the approved product is demonstrably less suited for vaporisation.
      Please don’t ask me about European law … I’m just a simple beekeeper 😉

      Stop press Chris kindly sent me some images which I’ve appended to the end of the post (above)

  4. Jason

    I’ve used Api-Bioxal with a Varrox. I put Kitchen foil over the pan and so the foil ended up charring rather than the pan. worked a treat and easy to clean; dispose and add another sheet of foil. I wonder if you could do the same with the sublimox? Although you would have to tear off a bit of foil with every/ everyother application, it’s quicker than cleaning the pan.

    1. David Post author

      Hi Jason
      I’ve seen others suggesting this and pleased it to hear that it works. I’ve not tried with the Sublimox. The pan gets very hot and the entire thing would need to be lined with foil (because you tip it over to ‘drop’ the Api-Bioxal into the pan). I suspect it would also have to be pushed tight down into the corners and the base to ensure good, quick and even heating. What’s irritating is that the additives that mess up your vaporiser aren’t necessary additions for treatment. They are irrelevant as far as the mite is concerned. It’s a perfect example of “progress” being quite the opposite!

      I’m hoping my Varroa treatment is completed this year – with a couple of exceptions mite drops are extremely low. By treating as early as possible after taking off the summer honey I’m trying to protect the winter bees from exposure to mites ad the viruses they transmit.


Comments are closed.