Size matters

Anyone reading the will be aware that there are a number of contributors there that enthusiastically recommend the treatment of colonies with vaporised (or, perhaps more accurately, sublimated) oxalic acid to reduce Varroa levels.

There goes a few pence ...

There goes a few pence …

Although vaporised oxalic acid (OA) has been used by some for many years, the speed with which it has recently been embraced by many UK beekeepers (at least those that contribute to discussion forums and, perhaps to a lesser extent, those I speak to in associations over the winter) probably reflects two or three things:

  • an awareness of just how effective oxalic acid is as a treatment
  • the increased availability of commercial oxalic acid vaporisers (or Heath Robinson-like plans to build-your-own)
  • the huge price-differential between oxalic acid and most other treatments

There are almost as many homegrown or imported vaporisers as there are treatment regimes to hammer down the mite levels. Of course, there’s the contentious point that oxalic acid is not approved by the VMD (Veterinary Medicines Directorate), despite having been in routine use for decades. Api-Bioxal is, but is probably unsuitable for sublimation due to the inert (as far as Varroa are concerned) additives it contains. Api-Bioxal can be vaporised but leaves a caramelised residue in the vaporiser pan that is hard to clean.

Out, damn'd mite ...

Out, damn’d mite …

‘Vaping’ is also popular in the US. Randy Oliver has covered it extensively on his site and it’s also regularly discussed on Beesource. OxaVap make/supply a vaporiser that appears very similar to the Sublimox I use. The OxaVap model has a useful temperature display that I would find much easier to read than the red/green diodes on the Sublimox … I’m red/green colourblind.

Active and passive vaporisers

The Sublimox and OxaVap vaporisers are ‘active’ … they blow out a dense cloud of OA-containing vapour through a relatively narrow diameter nozzle (the video below uses water to demonstrate this process). This provides advantages both in terms of ease and speed of delivery. These vaporisers simply need a 7mm hole drilled through the sidewall of the floor (see photo at the top of the page), or through an eke placed over the colony. The OA-containing vapour is ‘squirted’ in, permeates all corners of the hive within seconds and you can then move on to the next hive. The vaporiser doesn’t need cooling between treatments and the dose administered is tightly controlled.

Big Daddy

However, OA dosage isn’t critical. It has been shown to be well-tolerated by bees in studies from groups in the UK and Germany. If the dose isn’t critical and speed really is important then perhaps consider the vmVaporizer. At $3600 it’s about ten times the price of a Sublimox.

vmVaporizer ...

vmVaporizer …

The manufacturers claim you can treat 300 hives an hour with one of these … one every 12 seconds. For comparison, the Sublimox takes 20-30 seconds per hive. However, what takes the time is sealing the hive, moving the generator about, unsealing the hive etc. so you’d need a team of (well protected) helpers and some closely spaced hives to achieve a similar rate. The vmVaporizer is mains (110V) powered so would also need a generator or inverter.

The video above demonstrates the vmVaporizer in action. It produces copious amounts of oxalic acid vapour, albeit less ‘forcefully’ than the Sublimox. It seems the only way to control how much is delivered is by changing the duration the hive is exposed for.

Undoubtedly this is overkill for the majority of readers of this site, but it’s interesting to see what the commercial beekeeping community are using (much like browsing the decapping or bottling machines in the Swienty catalogue). There’s at least one satisfied UK-based beekeeper quoted on the vmVaporizer site so … Mark, if you happen to read this I’d be interested in how well the machine works and whether you can achieve the quoted hive treatment every 12 seconds?

And, does it work with Api-Bioxal?



8 thoughts on “Size matters

  1. Alan Jones

    Hi David,
    I have been using a vapouriser that I bought from Germany on e-bay for three years and am more than pleased with the results. I treat the hives around the 20th of December, three times at five day intervals.Please wear a chemical grade face mask as you really don’t want to breathe in the fumes. I also treat in August with a rotating alternative to prevent resistance and have really strong colonies in the spring.

    1. David Post author

      Hi Alan
      I’m not sure I understand why you treat multiple times in midwinter? Presumably you’re assuming the colony isn’t broodless and the repeat treatments are to ‘catch’ mites that were originally in a cell at the time of the previous treatment? The Sussex LASI group have suggested opening the colony midwinter and removing sealed brood prior to treatment. I’ve not done this.

      I discuss in other posts the need for personal protection equipment when using a vaporiser, but it’s certainly worth repeating.

      Because of the very different mode of action it seems unlikely that resistance will readily arise (as it has done for Apistan) to oxalic acid. It’s arguable, but oxalic acid-based treatments (and there are more coming to market soon) – if used properly and carefully – probably offer the ‘sweet spot’ when cost, likelihood of resistance, colony tolerance and efficacy are taken into account. In particular, in comparison to other soft chemical treatments like thymol or formic acid (Apiguard and MAQS respectively), it’s tolerated much better, with no appreciable effect on the laying queen for example.


      1. Alan Jones

        Hi David,
        I live on the Lizard in Cornwall, about as far south as you can get without actually falling in the sea!
        we have really mild winters and consequently there is some brood all year round, hence the three treatments. I can see the sense of removing any brood, but would not like to break up the winter cluster, just as I wouldn’t squirt liquid OA in with a syringe.

        1. David Post author

          The Lizard … lovely 🙂

          I agree about splitting the winter cluster up … not something I’d do. However, trickling oxalic acid works well midwinter, is pretty-well tolerated and is quick and easy. It even works with Api-Bioxal. For the 1-2 hive owner it’s probably a better option than vaporising OA. It’s worth noting that trickled OA is toxic for open brood, but sealed brood should be OK.

  2. Helen

    How effective in anyone’s experience is treating 3 times at 5 day intervals, with brood present?
    I read (bee keeper quarterly) that mites now emerge from a cell, and go straight into another to reproduce. Rather than spend time on a bee before entering a cell. If this is the case, it would then make the above vaporising pattern less effective wouldn’t it?

    1. David Post author

      Hi Helen
      I’ve used that regime and it seems to work well. I’ve counted mite drop after every treatment and it decreases significantly and is negligible at the end of the final treatment. The first person I’m aware of who published this regime was Pete Little of Exmoor Bees and Beehives who is Hivemaker on the Beekeeping Forum. I think Pete determined the schedule empirically.

      I don’t get BKQ any longer so don’t know the article. All the scientific published work I’m aware of indicates that mites are phoretic, primarily on nurse/hive bees (not foragers), for 5-11 days before re-entering a cell (obviously much longer if brood is absent). If this were not the case then the treatment timing would be incorrect as you suggest.

      The University of Michigan (Zachary Huang and colleagues) published an overview of the Varroa life cycle which includes the following quote … mites that do not experience the phoretic stage have a lower fertility, especially compared to those hosted by younger nurses ….

      I hope this helps.

  3. Calum

    Banned in Germany as breathing the vapours is very bad for your health. You could treat wearing a gas mask, but then beekeepers would lose the aura of being managers of nature. Arguments about pesticide use while we go about in gasmasks is so much harder to carry off….

    1. David Post author

      Hi Calum

      Yet driving at 270 kph on the autobahn is OK 😉

      The ‘managers of nature’ is a very interesting point. I think that’s an aura some like to project. I don’t see it that way, preferring to consider it as a team effort … working with nature.

      Whatever, the video is pretty irresponsible as neither user is wearing personal protection and that machine produces a huge amount of vapour. Being downwind of it would be both extremely unpleasant and very harmful.


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