varroa mites

How to torch your hive with an oxalic acid vaporizer


At first I thought this story was unusual. Debbie, a newer beekeeper who reported the incident to me, explained that she accompanied a seasoned beekeeper to his apiary to learn about applying oxalic acid with a vaporizer.

Here is her story, edited for brevity:

The one hive caught fire. It was hectic trying to get the boxes apart and watering the hive down to stop the flames.  The flames were shooting out everywhere. I don’t know if the bees will be able to recover or not.  He would not permit me to clean up the hive; he just put the hive back together, dead bees and all, and said the bees will fix the hive.

This is not how I do things, and I probably will not go with this person ever again.  It was disturbing to me.  If it was my hive, I would have cleaned it out, checked [to see] if the queen was still alive, etc. [I would] not just shut it up and leave the bees devastated as they were.

What else I didn’t like is…the bees continued to “attack” this poker and thus burn themselves up.…When you take the poker out, there are several bees on the end of the poker burnt to a crisp.

We did 35 hives and all did the same thing.  Some ran out of the hive so fast, it wasn’t even funny. [The bees] actually “attack” the rod [when] it’s hot, touch it, and the end just burns them up. I even asked the guy about why he thought the bees would attack something so hot.

The vapors will knock you out. The one guy I went with got a good whiff, and I had to catch him; he almost fell over.  I think one is supposed to wear a respirator, as breathing in these fumes causes one to cough and gag, and inside it probably does more harm to the lungs.  I tried to watch the way the wind was blowing and then stand on the other side.

Solutions to torching and scorching

Based on Debbie’s comments, I did a web search and learned that torching a hive with a vaporizer is not uncommon. In addition, many who don’t actually ignite the hive manage to scorch the frames and burn some bees. It seems that burr comb hanging down below the frames is the main problem. Such wax is easily lit by the hot metal vaporizer and explodes into flame.

Beekeepers have devised a number of solutions to these problems:

    • Some have found that using a slatted rack below the brood boxes increases the distance from the lower frames and accumulated burr combs, thus reducing the fire hazard.
    • Other beekeepers put a narrow three-inch shim on the top of the hive that contains an opening large enough to accept the vaporizer. This reduces the fire danger because there is no wax comb above the hot plate.
    • Some people wrap the sides and bottom of the vaporizer with aluminum foil, a system that dissipates heat and keeps the hottest parts away from flammable objects.
    • Some simply clear the burr comb away from the insertion area with an extra long hive tool.

My sexist remark for the day is this:  I know that a man—a male human—invented the vaporizer. It is so man-like to want big, powerful, macho equipment to do a wee little job. More power. More complexity. More hazards. Yay! One guy told me, “Some catch fire. So what? It is what it is.”

Whatever happened to the dribble method?

I learned to dribble oxalic acid from Randy Oliver’s website. Before my first application, I stalled around forever, obsessing over how to do it properly. Then I saw the video of Margaret Cowley of Bee Craft Magazine applying an oxalic acid dribble to her bees. She made it so drop-dead simple that all my hesitation disappeared. And it truly is as easy as it looks.

With the dribble method, there is no fire danger, no expensive equipment, no batteries to haul around, and no respirator needed. It is fast, dirt cheap, and it works. The biggest drawback, apparently, is that it doesn’t look very macho.

The vapor method works because the vapor condenses on the bees. The dribble method works because bees communicate and groom by touching each other. They quickly spread the stuff around the hive.

Endless discussion has centered around which is better, which is safer for the bees, which kills more mites, and on and on. You can find research and arguments to support either side. The latest research I read suggests that vapor may be slightly more efficacious. But my opinion is the slight benefit is offset by the many negatives.

Winter application of oxalic acid

One common argument for vapor is that you want to apply oxalic acid when little or no brood is present. That means you need to apply it in the dead of winter when it’s too cold to open the hives. But with a few exceptions for particularly cold places, I don’t see much problem with opening a hive for a couple of minutes in winter.

The main danger with opening a hive in winter is chilling the brood. But the whole point of applying oxalic acid in winter is to use the broodless window to kill the most mites. So with no brood in the hive to start with, a couple minutes of open time will not hurt anything. In addition, those of you with infrared imagers can apply oxalic especially fast because you know where the colony is before you open the hive.

Vaporizers are the current “bee thing”


Oxalic acid is an inexpensive organic acid used for mite control. © Rusty Burlew.

I completely understand that some of you are not concerned with toasting a few bees. I get that. But setting a hive ablaze should be a financial concern, if nothing else. Additionally, using a vaporizer in areas of extreme drought sounds foolhardy at best.

My personal dislike of vaporizers has more to do with the accumulation of stuff. I try to “travel light” and I resist purchasing specialty equipment when I can do the job with the tools I have. But regardless of your personal preference, I offer Debbie’s story as a warning about the things that can go wrong. Bottom line: If you vaporize, do it with care.

More on the dribble method

For more on the dribble method see “How to apply an oxalic acid dribble.” For Margaret Cowley’s video, see “Oxalic acid trickling.” Another good demonstration video can be found on Emily Scott’s blog, “Drizzling oxalic acid on bees.”

Honey Bee Suite

Discover more from Honey Bee Suite

Subscribe to get the latest posts to your email.


  • I made a bottom board that is screened and has a gap at the front so I can easily treat a bee free area and the vapors will rise through the screen.

  • I have done the dribble method and it works fine. I now use the Varrox vaporizer. I use double brood boxes and the bees tend to cluster between the two boxes. When I separate the boxes to do the dribble method I break the cluster and this is why I prefer the vaporizer. I am in Ontario Canada where the temps can be cool in the fall. I do not have to separate the boxes with the vaporizer. I use great care with the Varrox vaporizer (which is not cheap). I also use a mask and gloves. I have seen a lot of homemade vaporizers on the web and I wonder how safe most of them are?
    Thanks for another great article. A good reminder to use caution with the vaporizer.

    • Hey there,

      I just wanted to answer on Tom Nolan’s comment about the Varrox vaporizer. It has been developed by Mellifera e.V., a German organisation researching and developing methods for organic beekeeping:

      Varrox has been tested with over 1500 colonies with great success:

      Ironically this method is not approved by German laws, so German beekeepers take their bees regularly onto journeys to Austria and Switzerland.

      Because oxalic acid does not affect capped brood, beekeepers treat their bees 3 to 5 times in two weeks, so that one brood cycle is covered completely to catch every mite.

      Maybe you find this information useful,

      all the best,


  • I have never used one and I am not an organic beekeeper but I still have trouble getting past something called an “Oxalic Acid Vaporizer”.

  • This is what happened to me Rusty. Last year I vaporized one of my hives and when I saw the vapor looked a little heavy, open the hives to flames engulfing my hive. Heartbroken, I put it back together in form of a nuc and the next day looked for the queen. Didn’t find her so I went and bought one. The hive still didn’t survive. The actual acid holder container actually was burned off. So I bought a more expensive one and put on a slatted rack. So far, no problems. It seems Rusty with everything there is a risk of killing the queen or the bee’s absconding. But your article is food for thought.

  • Some problems and solutions with oxalic acid treatment.
    Here in the coastal pacific northwest, bees rarely go brood-less in the winter. The last time was December 2012. My hives had between 2 and 5 seams of brood at the end of last November.
    When brood-less, oxalic acid dribble or vaporization appears to give close to a 100% knockdown. Once vaporized oxalic acid immediately condenses into its anhydrous form, and the dust coats everything in the hive. In its dihydrate form, oxalic acid does not damage mites unless ingested by the bees.

    I use vaporization because it does not appear to damage bees at all, unlike forcing them to ingest the acid dribble. I also use an external vaporizer and re-circulation system to apply the dust, in order to avoid the heating and fire problem.

    My main concern with vaporization is not breathing the vapor (only a mad bee keeper would not wear protection) but the long term effect on the eyes. I see very few people wearing properly fitting goggles when handling acidic vapors.

    I am currently experimenting with caging the queen for two weeks and then treating a week later. If it works, it will be an inexpensive and effective late summer treatment. I would love to hear from people who have tried it.

    • I’d love to know how your experiments went. I’m currently doing the same thing. She’s been caged for 15 days and I plan to release her in 3 days and treat after 6 days.

  • Greetings from Scotland,

    If you look at the recent work of Prof Francis Ratnieks, et al, you will see that sublimating oxalic acid during broodless (if possible) periods is more efficient than the trickling method and is less harmful to the bees. Also less invasive.

    I have been sublimating for several years and place the evaporator under mesh floor on the outside as I have burnt frames in the past myself. Of course the acid is corrosive so I wear an appropriate gas mask. (not cheap, but anyone who is careless with chemicals is bonkers). I hope that this helps. Prof Ratnieks is based at Sussex University, UK and is speaking, alongside your very own Prof Seeley, at our Scottish Convention on Sept 10th in Elgin. There are still places so why not come along and join us for our tartan weekend. See Scottish Beekeepers Association website for details.

    Best wishes

    • No. As I stated in the article, I use the dribble method largely because I do not want to allocate money or storage space to the vaporizer, battery, and respirator. The expense of other mite control products is the main reason I switched to the oxalic dribble. But I’m repeating myself here.

      I should mention I have accompanied others who were vaporizing, which further convinced me to stay with the dribble system.

  • Hi Rusty:

    I have a method that seems to work for me. All of my hives have screened bottom boards. I take the trays out below the screens. I have made a tray out of a cheap metal cooking pan but any flat aluminum surface or foil will do. I put the tray in below the screen, close off the front entrance, and put the vaporizer on the tray below the screen from the back. I block the sides with rags and then vaporize. As for staying away from the fumes, I have a very long extension cord which I can switch on from the basement or the honey house.

    Hopefully this might be helpful for someone else.


  • I have been trying to find a good option for treating for varroa when using top bar hives. I live in the east of England and the winters lately have been mild enough for the queens to keep on laying, so being brood free at the winter solstice is not guaranteed. I have not convinced myself that breaking open the propolised bars is less harmful than leaving the bees untreated but have been trying to find out more about vaporising the oxalic acid and hence not needing to break open the colony.

    How do you treat your top bar colonies, Rusty?

    Thank you for your excellent site, I’m delighted to have found it.
    How do you treat your top bar hive?

    • Sue,

      Lately I’ve been using oxalic acid dribbled between the top bars. I have to take out a bar or two from the end, space the bars a little (which requires breaking the propolis seal) and dribbling between the bars. I have never considered breaking propolis seals an issue. Even in the dead of winter they reseal due to heat from the colony.

  • Don Coventry,

    An alternative to your method would be to take two hives and give capped brood to one of them and open brood to the other. Treat the open brood hive and let it be a receiver of all new brood from the capped brood hive for the next couple of weeks.. Eventually all capped brood will emerge and you can treat this hive too. Now take some capped brood from the first treated hive to help equalize the populations. Summer bees die so fast, you really loose quite a bit of hive strength by caging the queen. Thoughts?

  • Being a particularly non macho individual, I have found vaporising the most effective treatment I’ve used. It’s simple, less intrusive and quick. I’ve watched bees hovering in the vapour issuing from the entrance without any signs of distress. The knockdown effect is remarkable and the system is perfectly safe if the instrument is inserted beneath the ventilated floor, resting on a wooden board or similar. I don’t think machismo has anything to do with it, but then I don’t light my smoker with a blow lamp either.

  • You need to be careful when you use this stuff that you are not overheating it. It is suppose to vaporize and not burn. It will react with the oxygen in the air and start burning if you get it too hot. You should do a cold test outside of the hive to see how long your vaporizer takes to finish off a dose w/o burning, and then always use that time or less to do your treatments. All vaporizers perform differently, so it’s important to test your own equipment/battery/setup.

    • AJ,

      Excellent points. Thank you for sharing good information. I hope everyone tests their equipment before they start. It could save both bees and woodenware.

  • Does anyone in the states sell those oxalic acid containers with the treatment pre-mixed as shown in the videos?

  • Regarding your sexist comment that the OA vaporizer had to be
    designed by a man. I couldn’t help but think the same about leaving a burning smoker on a wood table. “Must have been a woman.”

  • I am a 2nd year beekeeper in canada, an my first year i used the dribbling method with good success. Both of my hives wintered extremely well. My problem with the dribbling method is that, because it can only be done once, one has to wait for the bees to be bloodless. That delays treatment untill very late fall or early winter. Everything i read says we should be treating in mid/ late August. Because the vaporizer can be used consecutively, it allows us to treat much earlier. That makes for stronger bees going into winter, rather than weakening our winter bees.

    I hav not used a vaporizer, but have been considering it. Thoughts? Is it that bad to treat winter bees? I did last year and they came through great, but we had an easy winter here.

    • Tyrel,

      Like many other beekeepers, I believe the best practice is to alternate treatments. I recommend ApiLife Var (thymol) in August and oxalic acid in winter.

  • Rusty

    After reading the story I can’t help but think these people did not properly research prior to using the vaporizer and possibly used a homemade version. Based on the description they did not block off the entrances with rag, If that is true then they were not performing the treatment correctly. I just started using sublimination. I bought my kit from mannlake. It came with very clear instructions plus a organic vapor protection mask. To say they had to catch someone falling over due to breathing the vapors and that maybe they need some sort of mask? I have to wonder if they were using 100% oxalic acid and not some other crystals? Unfortunately that story is full of mishapps that could have been avoided with proper instructions.

    On the dribble method an earlier poster spoke of forcing the bees to eat the acid in sugar water. This is incorrect according to what I have come to understand. The sugar is to make it sticky so the mixture is drug around by the bees as they walk around the hive. Then when the mites emerge they get the crystals on them and they die. Is that not correct?

    I like the vaporizer since it can be used in temps down to 34 degrees according to Dr. Marion Ellis if I am recalling his power point presentation correctly. The original person who had all the issues would benefit from watching the video.

    Do you have a write up on the dribble method, how it works and how to do it or do you refer people to Randy Oliver’s site?

    I found this blog entry when I searched for “vaporized oxalic acid not working ” this story is the closest I could find to people having issues.

    Thanks – love your blog – lots of great info.


  • I’m a 2nd year beekeeper in the Pacific Northwest. In November, I started the oxalic acid vapor treatment; 3 treatments for 3 hives, once ever 7 days. I am using a self timer vaporizer. I use a 12 vdc car battery with a plastic carrying handle. I go out early, plug up the top brood box entrances with wine corks. I have my bee veil on and wear disposable nitrile gloves. The vaporizer has a very long cord. I hook up the battery. I remove the mouse guard. I have screened bottom boards and the slotted spacer board above it. I place the measured spoon amount of crystals in the vaporizer “cup” and push the rod as far as it goes in, then tuck an old bath towel strip around it to seal the bees entrance. I take another towel strip and plug up the sticky board entrance. I also put in a sticky board when I vaporize. Okay, now I turn the toggle switch to on and go sit in a chair next to the battery, about 10-12′ away. The timer light goes out about in 5 minutes. I wait another 5 minutes, before going back to the hive and removing the vaporizer and towel strips and cork plug before moving on to the next hive. I don’t use respirators which I have, but I am very careful and watchful of the entire process. First mite counts in 24 hours after treatment with 3 hives respectively each week was: 1st 7,8, 32. 2nd 33,72, 74. 3rd 21, 39, 122! I didn’t have any dead bees except for the normal 3 or 4. My problem is wasps, trying to raid the hives. I’m going to vaporize treat again as I don’t like the mite counts at all. Perhaps this is why I had an almost nil honey super production this year.

  • We have some nice weather here in Minnesota so I went out to check on the girls and put on some more winter patties. Two hives were dead outs so I brought them in the garage to clean them up and I also wanted to check the frames after using the vaporizer. The wood was charred black on the frames that were over the vaporizer. Time to go online and do some research. These are very good articles, very informative. Last fall was my first time using the vaporizer and it is a learning experience. First I ran a test outside the hive for the 2 1/2 minutes as suggested and it vaporized all the xtls. No problem. However after doing 5 hives the battery starts to lose its punch and the time has to be slightly increased to vaporize all the xtls. I use a screened bottom board on top of a regular bottom board for ventilation and to monitor the hive. The method mentioned here for putting the vaporizer under the screened bottom board is excellent and should prevent fires and still be effective. Thank all of you very much for the help.

  • I have some apiaries that I want to take care of. I didn’t know that unprofessional application of oxalic acid vaporizer could be such a big problem! I don’t want to risk lighting anything on fire, so I’ll be extra careful with it.

    • John,

      I’ve been using the dribble method for several years with no ill effects. If you follow the directions, it works easily and safely.

  • I had forgotten about this posting. So many great ideas. They will help me in the following years. I am still not a fan of vaporizing.

    • Debbie,

      No, me neither. Basically, I refuse to do it. For me, it crosses the line from “relaxing hobby” to “industrial agriculture.” Ain’t gonna happen here.

  • Does anyone know what a reasonable mite drop after a solstice OA vaporization would be?

    I treated with MAQs in August and an alcohol wash post treatment was <1%

    My counts since vaping have been around 100 and dropping, each day for the 3 days post treatment so far. Seems highish to me, but I can't find any suggested numbers with researching the internet.

    I understand the mite boards aren't all that accurate but Im hoping the numbers could be a bit of a guideline for retreatment.

    • Carol,

      I don’t know but someone else might. I think the absolute number of mites will be related to the size of the colony, which is one reason mite boards aren’t all that accurate. I’m wondering if you had some drifting of mites into your hive after the MAQ treatment. I agree the count seems high, especially after the good results in August.

  • Thanks Rusty,

    I was thinking drifting was likely also….I followed the drop after the MAQS, and only had about 40 and declining to zero in 4 days on both hives. I have a neighbor with a couple hives and we share the vaporizer….but we are very rural and I have we have no idea if there are other hives near us….no one in the bee club is close! I did have robbing activity until I got guards this fall…I blamed my neighbor of course!!

    I’ve been surprised at my numbers now. It looks like the temp is going to hit 40 here today so I’m going to OAV them again, its the 6th day since the first treatment.

    Do you know how reliable/likely the “broodless period in late winter” is in the PNW? I’m a bit higher and so colder than you. Ha, I’m not going to pull frames to look.


  • Oxalic is hard on the bees just like any other mite treatment. Rusty, do you know of any research on it’s overuse? I have heard of people using it weekly and even in the depths of winter when the bees are clustered. Doesn’t seem like it would bee a good idea to disturb them when they are clustered. Seems these issues should be taken care of prior to the winter clustering. It makes sense that if one treats in August, there would again be mites by October. That is a given. But to keep using oxalic for a 0 drop constantly doesn’t make sense. I don’t think one will ever completely rid the hive of mites as they keep coming back from so many different sources.

    And, with regard to the comments about not using protection or researching, etc., one must remember, when you are relatively a new beekeeper and you go with a ‘mentor’ to work their hives, you must learn to keep your mouth shut … especially when you are dealing with ‘old timers’ who know absolutely everything. Just makes things move more smoothly. As one goes thru mentors, one discards the BS and keeps what is good. Every beekeeper is different in how they treat their bees. Some care. Some do not. My motto for the mentors who do not care is: ” I learn ‘what NOT to do’ ! ”

    If you follow the advice on this website, one will do well. It’s way superior to others and offers down to earth suggestions and instructions. It also has an exceptionally good forum that offers great information from other countries and places. Keep up the great work this year Rusty. Hope you had a great Christmas.

    • Thanks Debbie. As a matter of fact, I was just reading some research into overuse of OA vapor. It was only preliminary, but there is some evidence that sensory hairs on the bees’ antennae may be damaged by it. This would probably affect the ability to forage and to communicate. Like I said, it’s not published yet, but it’s good to know people are working to find the answers. Personally, I think it is stupid to use OA as if it were harmless. If it was harmless to living things, it wouldn’t kill mites.

  • I have been reading extensively with what I could find on recent internet bee site entries. People from the UK who have been doing this a lot longer use 7 treatments OAV 3 days apart. For years.

    A more reasonable system seems to be 3-4 treatments 5 days apart. In the winter, with no drone brood, 3 TX should cover all the possible workers if treated on day 1, 6 and 11.

    I didn’t want to treat so much, but after < 1% alcohol wash after Maqs in August, I had over 900 mites drop last week after two OAV. That’s 90 or more every day over many days. It’s not like 97% drop with one treatment, then nothing…….the new ones must be coming from emerging brood..The only way I can see to have somewhat low spring mites is to continue treating till the numbers quit. Day 11 is tomorrow and Im excited to see what happens after treatment.

    I’m feeling and seeing on my IR camera that the cluster breaks up and moves quite a bit after the OAV…I think/hope they are fanning like crazy and moving it all around. Do they ever quit moving in a cluster? don't they continually circulate?

    I’m wondering if the common solstice treatment advise is too late…I must have gotten drift from where-ever….Im thinking an early December treatment,and watching the drops might be more better!

    Please recognize..Im going into my second year…..I might know everything,…..:)

    • Carol,

      I’m wondering what your count was after day 11?


      P.S. I’m also in my second year but I know less now than I did my first year.

  • Well, Greg, the longer you are in it, the less you know ……. the more intrigued you get and it takes over your bee-ing ! As for Carol’s comments, if you treated in August, then of course you would have mites again in December. It’s a constant battle that never ends. I don’t think one would ever get to the point of having absolutely no mites in a hive. If you oxalic in December, and then start your drone trapping in February or March, you can get them buggers out of the hive before the bees start producing in earnst for spring buildup. You might want to read Rusty’s post on drone trapping. Always remember, even though people do something a lot and for a long time, doesn’t mean it don’t have any consequences for the bees. If you are oxalic’ing when they are clustered, and then after treatment they are moving around, then you have disturbed their winter cluster. Keep us posted as I am also interested in your mite drop.

  • Greg,

    After the day eleven treatment one hive went to zero.

    The other hive continued to drop 30+ for a few days and then 70! So I did a fifth treatment on day 16.

    The second hive has continued to drop more than 20 or 30, I may treat just that hive one more time. The other hive is still at one or zero drop.

    Our weather has been up into the 50″s and the bees are flying a lot, Ive wondered if their moving around more and cleaning up is knocking already dead mites off the comb and slatted racks?

    I think I may have mite related OCD? Its becoming a thing. Ive seen some literature from the UK relating 7 treatments three days apart as a normal routine.

    Our bee meeting president has had a similar experience…low alcohol wash in late August but surprisingly high counts in December. Next year I will be checking mite boards/alcohol washing in October to see whats up. I will also use my robbing screens all season. I didn’t know, so didn’t get them on till late this year and had some ongoing low grade robbing for a while…which I assume brought the little buggers.

    Any other suggestions?


    • Well both of my hives are now dead. The first one went in December but it was showing all kinds of signs of CBPV since June and the numbers just kept dropping all summer fall…and I felt completely unable to help them. I used oxalic vaporizer when mite counts looked boarderline and swapped out drone frames every 30 days. Both of my hives had very low mite counts (sometimes zero) all spring through September so I thought I was going to be fine this winter. Big mistake! I just inspected my remaining hive and it had all of maybe 50 bees still alive – clustering around a dead queen. Very sad. I see Varroa on almost every live bee. I was of the very wrong impression that having really low mite counts in late September meant I didn’t need to worry until spring. 🙁 Time to start all over again.

      • Gregory,

        It’s hard to get a good mite count when there is lots of brood in the hive. Using a sugar roll or alcohol wash will help, if you’re not already doing so. The old rules about mites don’t apply much anymore. Treating once a year used to be enough, now multiple treatments are often needed, depending on local conditions. Do start again; it is worth it.

        • Thanks for the encouragement Rusty,

          Yeah I did my first sugar rolls this summer and it does seem to help with getting a more accurate count than with mite drops on sticky boards. I just ordered two more packages of bees. I’ll start again this April and will be much more vigilant on mite counts throughout the fall/winter.

  • Oh, I wasn’t expecting the counts to be zero in December. I had assumed a one time clean up treatment to get rid of most phoretic mites while there was low brood and that would be it till spring.

    I wasn’t expecting a thousand mites.

    There must be more bees, mite bombs, up here in the hills than I knew!!


  • Ha ha! It’s a never ending battle ! It will drive you crazy if you let it. We’re waiting on Rusty’s post about ‘oxalic overload’. How big is this hive? Do you have an estimate of how many bees you believe are in there. The mite drop doesn’t seem that large for a huge colony. Usually the drop is quadzillons ! I am just curious as I am learning all about them as well, but I don’t treat but a few times a year. It’s unnecessary for us to treat more than 3 or 4 times a year, depending on the mite load. And we start our drone trapping in February, weather permitted, to alleviate putting anything in the hive before the main flow. Hopefully your hive will pull through. It’s not as much mites you have to worry about, as the virus loads they carry. Once you have mites, you have virus, it’s a given. I don’t believe you ever get away from them.

  • I sent a post but it seems to have been lost to the ‘wherever,’ so if this is repeat I apologize.

    I have been treating OAV every 5 days since 12/22. One hive got to very minimal drops after Tx 4

    The other hive kept dropping a lot, and after this last day of 63 degrees, dropped 150 in one day. I did a sixth OAV on that hive and have finally gotten low single digit drops.

    I attribute the 150 drop to the increased activity and housekeeping of already dead mites. They were bringing in pollen and dumping dead bees that day. (Jan 17th)

    I attended the Randy Oliver talk in Everett last fall and have notes that say 3-5 treatments of QAV at 4 day intervals needed to be effective. Well, I did 6 Tx at 5 days and finally got low numbers. I totally understand that the mite board drops are not really great, but it IS a measure after so many consecutive days. (I have no life I guess.)

    I can also say that the clusters, by IR camera subjective measure and debris on the boards, and not just the on warmer days, are increasing. I don’t think the two hives ever went broodless, hence the continued mite drops and needed repeated treatments.

    I will be alcohol washing as soon as the weather permits this spring. I also just went ahead and put on the robber screens, it was so warm and the bees were actually bearding a bit. I figured better safe than sorry. I don’t want to deal with those low grade robber/mite drifters again.


    • Carol,

      I find it interesting that people see such variable results with OA vapor. I think the only thing to do is what you did: keep treating and keep testing until you get where you need to be. You can’t just treat and assume it will be okay.

  • Gregory, please go and study Rusty’s post on “Two Beekeepers Watch their Hives Abscond”. That will be a great posting for you to learn and read thoroughly. Once you read that post you will be more savvy re: mites.

  • Just a side note, today’s ABJ article about lithium had a paragraph that said: It should be noted that studies have shown oxalic acid to be inconsistent at managing mites during the summer months as well as in colonies with capped broods. It provided a link, but for some reason I cannot get the link attached to this. Maybe Rusty can if she gets the article. Here is the abstract below. It is a little outdated, 2002. I have found oxalic to not be effective as well and had to use other methods for a better drop.

    Format: Abstract

    Send to
    Vet J. 2002 May;163(3):306-10.
    The control of Varroa destructor using oxalic acid.
    Gregorc A1, Planinc I.
    Author information

    Veterinary Faculty of the University of Ljubljana, Gerbiceva 60, 100 Ljubljana, Slovenia.


    Twenty-four honeybee (Apis mellifera) colonies were used to monitor the efficacy of a solution of 2.9% oxalic acid (OA) and 31.9% sugar against the mite Varroa destructor. Mite mortality was established prior to and after OA treatments, which were conducted in August and September. The treatments resulted in 37% mite mortality as opposed to 1.11% in the controls. OA treatment conducted in September on previously untreated colonies resulted in 25% mite mortality. OA treatments in October and November resulted in approximately 97% mite mortality. These results suggest that OA is effective during the broodless period and less effective when applied to colonies with capped broods. The possible use of OA against the Varroa mite in honeybee colonies as an alternative to routine chemical treatments is discussed.

    • Jeff,

      Oxalic acid dihydrate which is used for oxalic acid treatments runs about 97% oxalic acid. Rhubarb leaves are approximately 0.5 to 1% oxalic acid. In other words, they are useless.

  • Hi Rusty,

    Have you heard of the Aluen Caps in Argentina? They have been discussed on Bee-L a few times. Not registered as an OA delivery method in US but are very similar to Randy’s paper towel method but with considerably more testing in Argentina. My friends in Argentina swear by them. There was a July 7 note in Bee-L from Robert MacKimmie describing his method of making the strips. These seem like an ideal way for long term OA treatment with minimal risk to beekeepers and ease of application. I’m surprised no one has registered them for sale in the US. I plan to give them a try this winter. Glenn

    • Glenn,

      Simple solutions rarely get registered because the process is way too expensive. If a company sees they will barely be able to clear a profit after all the red tape, they won’t touch it.

  • Rusty,

    If you have a slatted rack, any reason you couldn’t place the hole for a provap vaporizer between the slats? That way frames would never be in the way. Or do you think that would be too far below the cluster?

  • Thanks Rusty, I wish I’d read this yesterday. Today I’m wishing I’d never seen that vaporizer, looking at a big setback, and shopping for a new queen. I had recently done a complete rehive for spring and had a slatted rack, which caught in the fire, so I don’t know why it burned but it did. Thankfully the weather was damp and I had water on hand.

    • I haven’t done this thing. Pretty sure that’s only because I’ve never gotten up the courage to USE the vaporizer I bought One Hundred Years ago. I hear we’re going to have oxalic acid strips soon, and I’m looking forward to that.

      I guess what I’m saying is be kind to yourself—forgive yourself. Pretty sure we’ve all made some beekeeping mistakes, so you are not alone there.