varroa mites

How to use oxalic acid & glycerin strips for varroa

Randy Oliver's varroa mite treatment using a mixture of oxalic acid and glycerine.

This post, first published in 2017, explains the why and how behind Randy Oliver’s varroa mite treatment featuring oxalic acid and glycerine.

Inside: Disposable shop towels soaked in a mixture of oxalic acid and glycerin may be the next reliable varroa mite treatment. It’s cheap, fast, and effective.

For beekeepers who treat beehives for varroa mites, oxalic acid has become the default favorite miticide. Oxalic acid is inexpensive, a natural component of honey, safe for bees when used as directed, and drop-dead effective. But being beekeepers, we can’t agree on anything, so the disagreement about how to apply oxalic acid rages on.

The US Environmental Protection Agency (EPA) currently recognizes three ways: spray, dribble, and vaporization. The spray method works on packages, but disagreement about dribble vs vaporization for complete colonies continues to fester. Being fundamentally a minimalist, I prefer the dribble method (less equipment, less expense, less danger) but each time I say so, I get trounced by those who thrive on great clouds of toxic fumes. Whatever.

Randy Oliver to the rescue

But now, biologist Randy Oliver offers us hope in the form of a disposable shop towel soaked in oxalic acid and glycerin. In fact, I have received so many questions about Randy’s new system, I’ve decided to write a short summary of his findings. However, I highly encourage you to read his paper in full, which details his methods, results, and statistical analyses. It also contains many photos.

The original idea for dissolving oxalic acid in glycerin came from elsewhere, but Randy took the idea and refined it. He tried various methods of delivery to find the one method that would be safe for bees and beekeepers, deadly to mites, and both economical and quick. So far, his new method has exceeded his expectations, and, much to his credit, Randy is now working to get the method endorsed by the EPA.

The basic idea for the mixture

The original research showed that dissolving oxalic acid in glycerin provided a way to slowly release the oxalic acid over time. Unlike dribbles or vapor where the dose is applied all at once, the oxalic/glycerin mix provides a slow release that is remarkably effective against mites but easy on the bees. Randy has been able to extend one treatment to last about 30 days, which means multiple treatments are not necessary. Mites die as they emerge from the brood cells without repeat applications.

Randy has amazing photos of his bees raising brood all around the soaked towels, seemingly unaffected by their presence, yet the mite kill is spectacular. After about 30 days, the bees have removed the entire towel from the hive so the beekeeper doesn’t have to re-enter the hive to collect them. It’s the closest thing to magic I’ve seen in a while.

What is oxalic acid?
Oxalic acid is a naturally-occurring organic compound. In its pure form, it is a colorless crystalline solid that dissolves in water. Many foods contain oxalic acid, including buckwheat, parsley, rhubarb, spinach, beets, cocoa, nuts, berries, and beans. In industry, oxalic acid is often used as a cleaning or bleaching agent.
What is glycerin?
Glycerin (or glycerol) is a sweet, non-toxic colorless and odorless liquid. It is widely used in both the food and pharmaceutical industries for a variety of purposes, including as a binder, thickener, sweetener, solvent, and humectant (a product that retains moisture). It is typically derived from soy or palm but can also come from tallow.

The supply list

Here are the supplies used in the experiments. Some are listed in the article and some I assumed. Plastic, glass, or wood utensils are necessary since metal can be ruined by oxalic acid.

  • Oxalic acid dihydrate (wood bleach)
  • Food-grade glycerin
  • A flat plastic tray for soaking the towels. Randy recommended two 12 x 14.5 x 2-inch InterDesign Refrigerator and Freezer Storage Organizer Trays.
  • Blue disposable shop towels. The article doesn’t specify a brand, but Randy says his towels fit nicely into the above trays. Looking over various offerings, I found that Scott 75143 Original Shop Towels are 11 x 13 inches, so I assume something about that size would work.
  • A scale for weighing the oxalic acid
  • Heat-proof glass measuring cup for measuring and heating the glycerin and mixing in the oxalic acid
  • A plastic or wooden spoon or spatula for stirring
  • A glass jar with a plastic lid for leftover solution
  • Chemical-resistant gloves (nitrile)
  • Protective goggles

How Randy prepared the shop towels

Randy is quite clear that he is still refining the method, but here are the steps that worked for him in his summer hives. Testing on winter hives is still underway.

  1. Wear chemical-resistant gloves and protective goggles when using oxalic acid.
  2. Use 25 ml of glycerin, 25 grams of oxalic acid, and one shop towel for every hive.
  3. Stack the shop towels in the plastic tray.
  4. Heat the glycerin in the microwave until hot but not boiling (about the temperature of a cup of coffee).
  5. Stir the oxalic acid into the warm glycerin, mixing thoroughly.
  6. Pour the warm mixture over the towels in the tray.
  7. Once saturated, Randy moved the towels to the second tray to drain. He says, “Squeeze or press them until you’ve recovered half the solution.” This is important for achieving the proper dose and encouraging the bees to remove the towels.
  8. Store the remaining liquid in a glass jar for later use. Randy warns that the liquid became quite blue.

Once ready, Randy placed one towel across the top bars of the lower hive body of each hive.

Be sure to read the whole article

Remember that this post is my interpretation of what Randy wrote. Be sure to read his .pdf for all the nuances that I may have left out. Also, remember that this method is not yet approved by the EPA and is therefore illegal.

Rotate Your Treatments
Like any other mite treatment, oxalic acid must be rotated with other treatments to prevent or delay resistance. Reports that mites are somehow unable to develop resistance to oxalic acid are completely unfounded.

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  • We know this treatment making stripes using cardboard for many years, comes from Argentina Mr.Prieto of apiary Los Alamos, the queen breeder of famous NAVEIRO line, invented this form.

    Resistance against ACID is nearly impossible. Only if mites getting a grosser shield. But this never could be observed in the past.

    • Oliver,

      Yes, resistance to acid is nearly impossible, but we don’t yet know if the mode of action is pH or if it is something else. Many beekeepers assume that it is just the pH, but assuming is not knowing. Until we know for sure, the precautionary principle is advised.

      • We know the mode and PH is not a factor.

        – Oxalic acid well known effect is that it reduces (oxidizes) calcium (and other metals), mites have/need free calcium on their mouth and feet as it is used in chemical communication (taste & movement).

        The reduction of that free calcium ( the same reason some people shouldn’t eat spinach) binds Ca into CaO and releases a lot of localized heat.

        Both effects interfere with the mites’ ability to move and locate feed.

        The Ca in a bees exoskeleton is bonded in chitin so the OA has little effect on honey bees unless they consume it.

        • DW,

          When you say “we” know, who are we? Also, can you cite a paper or study? I would love to read it.

    • I have used the towels method for two years with great success. This year I migrated my bees to NC. for the winter. Upon inspection by local authorities I was informed that this method of delivery of OA was illegal and was ordered to remove all towels immediately. However, vapor and dribble methods were acceptable. Could I spray a mist of OA and glycerin on the brood frames and nurse bees. Or is there another way to apply the OA and get the extended release effect.

      • Please see the March 2022 latest report by Randy Oliver that all beekeepers should read, irrespective of their expertise. The report since 2021 is of the utmost importance to bees. If the beekeeper follows the findings of Randy Oliver it will be seen to be the most efficient control without the use of manufactured insecticidal products. From the UK. I would ask what on earth is the opposition to a solution administered on an adsorbent sheet compared to spraying the stuff directly on the insects?

        It would be interesting if a researcher gives the answer to the question why does this method work when a 1-to-1 solution of oxalic acid and food-grade glycerine put onto an adsorbent sheet work better than fumigation or dribble methods?

  • Hi Rusty,
    You end with a note saying, “Reports that mites are somehow unable to develop resistance to oxalic acid are completely unfounded.” Have you come across any reports indicating resistance? I’ve been searching the internet for data on that very topic and haven’t found much.

    This new method Randy Oliver is trying is intriguing. I’ve downloaded his article and look forward to reading it. I’ve been fortunate to hear Dr. Rangal and Liz Walsh both present their findings on the effects of miticides on queens. Liz doesn’t seem to be a fan of oxalic acid, so I’m hoping the A&M Honey Bee Lab will be able to include research on it in the near future.

    Thanks for keeping us informed on the latest in our battle against Varroa.

    • Laura,

      No, I haven’t read of any pockets of resistance. But OA treatments weren’t legal in the US until recently, so they weren’t widely used. As more and more people use them, the selective pressure will increase. One problem in particular is that we don’t know the mode of action of OA in varroa mites. Some people think it’s merely the pH, but others think it’s more complicated. Until we know, it best to operate on the safe side and use the precautionary principle.

      • I am an engineer and have through my quite long life had to be precise so as not to blow up a room full of folks! I am new to beekeeping but seem to have done quite well in the circumstances regarding not being told about the threat of varroa mites when I bought the first colony of bees in July 2021.

        To cut a long story short, I have killed well over a thousand mites on the second colony I bought in June 2022.

        I paid meticulous;ous attention to a few on YouTube regarding the experiments they did with the oxalic acid strip method.
        I chose a 2 1/2 ” strip that dangled down between the frames x 2.

        I first fumigated the new hive but got an 80 drop after three days. A week later I installed the strip and the next day got 300 drop! I count every day what’s dropped and as Randy Oliver found his counts were erratic. Some days there would be far less and other days the count would go up but then towards the end of the first month, the counts went down and are now three per day.

        The first obtained colony were free of mites for three weeks but were then again infested with a few mites up to 10 in one day. They are now down to between 3 and one per day’s drop.

        If Randy Oliver says it can be possible to arrive at no mites and I do believe that. I base that on my observations so far. I am not too concerned about why the system does seem to work but take comfort in the fact that others and myself see that the method works to kill those horrible cretins.

        The first hive has exploded with bees and has produced 40lbs of honey this mid-July 22…… I am over the moon but am not prone to wishful thinking because I will be keeping a close check on everything that drops on that sheet which has been in place since day one. I felt that idea re the OMF was a damn good one.

  • Rusty can u or someone convert 25 ml to us measurments and what would 25 grams be is that tablt spoon cup i can not find the answer on the web thanks

    • Frances,

      It’s easier to just use a measuring cup and scale that has metric measurements. Many have both scales on them. 25 ml is about 5 teaspoons. 25 grams is a little less than an ounce by weight. But you don’t want to get this wrong or you could end up hurting your bees. You can get a scale that measures tenths of grams for less than $10 on Amazon.

    • I bought my digital scale at Smith & Edwards in Far West (my second one anyway, my first from a smoke shop) and got my syringes (free) from Walmart Pharmacist for the 25 ml ( about #/8′ diameter by 3′ long) mixed in styrofoam cup ( or glass I’m told) in microwave for 30 seconds (on high), then dribbled on blue shop towels, then placed in ziplock baggies until I could get bee suit on (and get my courage up) then placed on top of my two hives and left there for 10-14 days then removed during next hive inspection. good luck. mixed up on 5-29-17, & placed on hive frames, removed on 6-10-17. i plan on doing a powdered sugar mite count (w/ assistance of Utah state dept. of Agg. bee inspector-of course) next weekend (7-1-7/4) hopefully get low mite counts…

      • Dave,

        I think I see a flaw in your timing/application of the OA. My understanding of the towel method of treatment is to allow for longer slower release of the OA into the hive as opposed to the one shot deal with vaping. If your removing the towel after only 14 days, I think your missing part of the benefit from applying through this method. As is, I think most people using the vapor method apply three times 7 days apart in order to get all the capped brood but if you removing he towel after 14 days, aren’t you missing some brood? The method with the towel was also meant to have the bees chew and remove the towel over time which allows for the slow release and disbursement of the OA brood emerges as opposed to you removing the towel yourself. If you read the article, Randy goes into great length in finding the right proportion/consistency of the towel in order for the bees to be able to chew up the towel themselves.

        • It is such a shame there does not seem to be an up to date article and it is frustrating the idea of the extended release 1 to 1 oxalic acid and glycerine is not current to date.
          I see there is a Scientific Beekeeping ‘paper’ labelled part 1 by Randy Oliver.
          He is such an exacting individual being as he is a biologist that it seems incredible the way of distributing oxalic acid onto mites without any adverse effect on the bee colony has not had approval from the Authorities?
          A professional beekeeper is most probably correct in his assumption and forthright ideas when he says = there is no money in the idea =oxalic acid because it’s so cheap! Right on Harris……. Keep killin the damn things.
          Any beekeeper who loves bees will do anything possible to help the bees,
          and even if it means stepping (slightly9 out of the legislation.
          It is within the legislation to spray the Oxalic acid onto bees directly & so it seems faintly ridiculous to suggest the acid cannot be administered more slowly by a fibrous mainly organic harmless flexible sheet !
          Especially as the acid has been used in Europe since who knows when!
          I would be with Randy Oliver when he says a hive can be seen to have zero mites with careful application of the ‘strips’. Not only that finding but the observation that the colonies ‘saved’ from the mites that pass on the horrible viruses, are seen to be stronger in numbers than those hives which have not received ‘help’.
          One anomaly, looking at the application of oxalic acid is that fumigation, which it would be thought of and expected to be more searching than any other method is not as effective as the application of the same acid.
          I consider Two figures that influence my reasoning. 300+ after one day of a single strip being put in the single deep brood box as compared to three days after fumigation with 4 grms of O acid = 80 mites dead.
          The current to date count is 24 mites per day.
          If the previous experiment where 24 mites per day went on for quite a few days that month of ‘strip’ treatment in another hive then within a month a
          reduced fall of perhaps 4 per day until total eradication is seen to occurr.
          Randy Oliver is correct in saying zero mites can be achieved.
          Although the strip method of application has not been heralded by a fanfare of trumpets, as yet, I hope it soon recieves the accolades it rightly should do. .

  • Hi Rusty! Another wonderful article!! Thank you! I’m lucky enough to live close to Randy Oliver and my local beekeepers association is offering an advanced beekeeping class in April that will be taught by him and which I will be attending. If his OA method isn’t part of the class I will be sure to ask him about it.

  • Presenter wasn’t quite clear—did he use one shop towel per brood chamber or one towel per hive (2 brood Chambers)?
    Having been a research Biochemist, I truly appreciate the amount of effort that went into this research, Kudos to Mr. (Dr.?) Oliver and his crew.

    D. Dtoffel

  • Thanks Rusty, that’s very interesting.

    I’m based in New Zealand and we are coming out of the worst season in 2 decades, almost no stores let alone excess honey, will be a long winter ?

    However varroa has flourished this season so I’m keen to try this, but am trying to work out what a shop towel equivalent is here, are they a thick paper towel or an actual fibre towel? This is all I can find, should work ?

    • Graeme,

      Your source seems to be a little larger, but I think they would work. Shop towels are often sold in automotive stores, so that sounds right, too. They are like a strong and thick paper towel. And if you wanted to cut them a little smaller, you could.

    • I am a new beekeeper as of July last year. I’m a very old engineer and like to delve into how anything works plus I’ve always said if I cannot buy it I will make it! I have saved loads of money over the years and enjoy tig welding stainless still at 81. Luckily my eyes are still ok.

      It dismayed me that the beekeeper who sold me these incredible Buckfast bees did not ever mention Varroa. I checked them with icing sugar twice without seeing a single mite. I saw two dead bees in December with the DWVirus & so gathered that they may have varroa on them. I’d already made an accurate fumigator in case and fumigated them with OA 5 Dec. I made a stainless open mesh floor 40mm above the supplied floor from day one.

      I counted 60 mites on the cooking oil white plastic sheet that is checked in any case every week. The check was three days after the fumigation.

      The bees have been pampered re heat ( not too much heat though) due to me having a rad in the greenhouse the hive backs onto.
      I read Randy Oliver’s paper on the absorbent strips & noted he said the test strips were more efficient between the frames rather than above the frames.

      My wife bought me some ‘Multy’ brand 2mm gauge yellow fibre cleaning cloths that have 30% cellulose and 70% polyester in them (made in Holland.

      I feel they are just the job and are stiff enough to slip down between the frames.

      I have counted the mites that drop and have found the number of dead mites has increased over a weeks treatment.
      The count went from 18 to 20 most of the week but the last count on the 7th day was 44.

      I am wondering what other beekeepers who use this undoubtedly efficient method are finding re the various numbers? I found the strip method with 1 to 1 OA and Glycerine to be more efficient than 2 fumigations 7 days apart because I got less mite drop with the fumigation method than with the strips that Randy Oliver calls the OAE, the e being extended of course. (So many abbreviations these days which can confuse us lot who are not ‘smart’)

      Is my theory correct in that after a number of days more bees obtain an anointment of OA & there fore expose more mites to the acid. I note that there was 50% light coloured mites dead on average but that number is increasing………. I feel that seems good due to that fact meaning the acid is killing more young daughter mites ?

      I noted that Randy Oliver who is exceptional in his research said “it is possible to arrive at the time when there are no mites in a hive treated with the OAE. I for one am of the opinion that I should aim for. I have a similar attitude to rats and grey squirrels. I blame them for passing on Lyme disease to me October 2020. I hate em just as I hate Varroa.

      Exterminate Exterminate as the Darlek said!

      The authorities should ‘get their finger out and pass the needed legislation, tout suit, so that all those who know what Randy Oliver has proved can get killing mites as he has done……. Authorities =look sharp please!

  • Rusty, I can’t thank enough for your blog. It has been a constant source of wisdom, perpective, comfort, and chuckles. And this … this is exciting stuff! I’ll be trying it this summer for sure! Thank you again for your great service to bee-kind.

  • Hi Rusty,
    Can you please comment on using OA in regards to harvesting honey. Is there a specific time to wait once the treatment is completed before you can remove honey safely from the hive? What would be the best time frame (what months) for treating a hive so you can harvest honey?
    Thanks very much,

    • Mark,

      The EPA label is the law. It says, “Do not use when honey supers are in place to prevent contamination of marketable honey.” Since it says no more, I assume you can apply supers as soon as the treatment is complete. The best time to treat is going to vary depending on where you live. I generally have my supers off buy the end or June/first of July, but things may be different in your area.

  • In previous oxalic vaporization, it was necessary or suggested to remove the honey supers or place a barrier between the brood nest and the honey supers. After reading Randy’s information, I didn’t see any reference to this in this new treatment. Can this new method be used while honey supers are on?

    • David,

      Because no difference was mentioned, I would assume the safety measures would remain the same. That is, I would use this method before or after honey supers.

  • Thanks for the great info Rusty. Will put this method to work when season gets underway.

  • Rusty,

    Very interesting article. Certainly sounds like a promising safer way to treat for the mites.
    I would only caution one thing. You mention the glycerin should be hot but not boiling. That leaves a lot of room for interpretation, as the boiling point of glycerin is around 554 degrees F. A different way of putting it would be to use a thermometer and a specified temperature range.

    Very interesting article.

    • Fred.

      Hmm. Good point. I added Randy’s description to the post. He says to heat the glycerin until it’s like a cup of hot coffee. That would be a bit less than 554 🙂

    • There is no reason to heat the solution any more then to dissolve the QA. Higher temperatures can change the OA (reduce it) so- 120f is the limit I use.

  • Graeme,

    A shop towel is simply a very strong, fibrous paper towel.
    I’m interested in the method of draping the towel. I’m a TBH keeper and this method could easily be adapted to drape over a bar holding brood comb.

    • Dear Shawn,

      I’m sorry it’s a long time since the post. Also I must stress I’m a new beekeeper but as an engineer I see that the 2mm thick yellow ‘Multy’ brand cloths 30% celulose 70% polyester may be just what you are looking for. I cut these 400 x 300 ‘cloths’ ( which are just pence to buy) into 2-1/2″ x 10″ long and stuck a wood tooth pick 1/2″ down from the top as ‘they’ do with Apivar strips as they do not like the bendy bits and no wonder (who thought of that one?) Ah well it’s kept me busy for a life time often altering what manufacturers have made and sometimes for the better, hopefully? This absorbent fibrous sheet is not floppy as a shop towel and lends itself admirably to this project. Keep killing those varroa.

  • Great information, Rusty. This could be a really useful way to apply OA in a single treatment. I haven’t heard of this before

  • Rusty,
    Thanks so much for bringing this article to our attention. I am also from NZ and presently use OA vapour treatments and see this as an alternative to that. I lost all 4 of my hives to varroa infestation last year even with OA treatments – my problem though, not the OA. The varroa got way too far ahead of me to save the hives. So far this year I had to start is a queen cell and a shake of bees from a local beek. I am back up to 3 hives now, although we have had a terrible summer for the bees this year. Thanks again for our website and your time creating and collating all this good information. Cheers!

  • If one looks at Mr. Oliver’s article, which I’d encourage anyone wanting to know the specifics of his technique and its development to do prior to using it, it’s evident that strips hung between the frames as the Argentinians did produced a somewhat longer-lasting effect than his shop towel method. The driving force behind using shop towels laid across the top bars was good effect with maximum convenience, as there’s no need to reenter the hive to remove anything; the bees take out the trash. Making the OA/glycerin solution involves heating the mixture to 150 degrees Fahrenheit and holding it near that temperature for several minutes until all the OA has dissolved. Esteban, on the TECA site, describes a 60% w/v solution, Maggi, et. al., in their paper describe a 33% w/v solution, and Oliver describes a 50% w/v solution in his ABJ article. Glycerin is flammable and OA is dangerous. Don’t overheat the mixture trying to dissolve it; take your time. Don’t heat it directly over a flame or heating element. Don’t heat it in metal or plastic. I used heat-proof glassware and a water bath (large Pyrex measuring cup set in a few inches of water in a crockpot on high). Wear chemical resistant gloves such as you can find in the hardware store and use goggles. Glycerin can pass through your skin, so immediately rinse it off well if the solution gets on you. If it has OA dissolved in it, you may get a nasty chemical burn and/or suffer OA poisoning or kidney damage. Having a jug of water with a good quantity of baking soda dissolved in it to use as a neutralizer if the OA/glycerin gets on your skin, as Mr. Oliver recommends, is a smart idea. The effectiveness of OA seems to be related to getting it on the bees where it can damage the mites. The other application methods do this, whether via a fog condensing on everything in the box (heated vaporization) or dribbled in sugar syrup. Esteban and Oliver both note that the paper fiber carrier has to be superficially “dry”, not with excess liquid on the surface, or the bees avoid it and then it has little effect. Drywall shim strips might make a good carrier if one wanted strips.

    • Cal, you don´t need to heat the acid, I never did it, no need for it.
      Oxálic heated too much will transform in formic acid (gas!!!!) that´s why it correct to warn from heating the acid.

  • Rusty, USA is lightyears behind Europe in Varroa treatment. There they use the acids for decades and no resistance was observed. I think we can forget this point. More interesting is the correct use of treatments. A suisse study shows that the maiority of losses occurs with hobby and small beekeepers, professionals haven´t high losses caused by varroa.

    • Mary,

      The don’t eat it. They rip the paper apart with their mandibles and dump it outside the hive.

    • Bob,

      I would just lay the towel over the top bars if you have room, otherwise I would drape it over one of the bars and let it hang down on either side.

      • Ok so at the risk of being annoying….if I just lay it across the top will the vapor just go up and out rendering it ineffective?

        • Bob,

          It’s going to depend totally on the shape and style of your top-bar hive, since they are all different. My top-bar bees spend a lot of time in their attic, since that’s where their feeder is. I imagine that as they travel back and forth to the feeder, they will eat away at the annoying towel. But if your top-bar hive doesn’t work that way, you will have to do something different, like hang the towel over a bar.

        • Bob, this method relies on contact with dissolved oxalic acid (OA), not vapor. The glycerin is used to dissolve the OA and hold it within the paper towel. It may sublime very slowly, but you should perhaps think of this as an extended oxalic acid trickle, not a vaporization method. I think the only reason that Randy mentions using it in warm summer hives is not for vaporizing the OA, but rather because when the glycerin/OA solution cools sufficiently, it develops crystals – the OA comes out of solution potentially rendering it much less effective.

          • Dear Dawn,

            I think, and I hope I’m correct ( because being correct and exacting is something that gives me the feel-good factor) that these lovely incredible Buckfast bees are being anointed with the horrible (in my view) oxalic acid due to them rubbing against the fibrous 2mm thick sheets and therefore transferring that sticky acidic fluid onto the mites.

            I say this because the daily average drop has no mites alive in the 18 to 22 mites per day but has now risen to 44 yesterday. And above 50% are light in colour thereby suggesting the mites are getting younger that are killed. There is nothing I like better than killing loads of young female mites! I ask myself when will it be that the numbers begin to tumble? I should like that advice from other oxalic acid and glycerine at 1 to 1 extended-release strips which would be comforting, to say the least.

            I consider the correct procedures to get this excellent method that Randy Oliver has hit upon that he may well have obtained from the EU but seems to have refined his method somewhat.

            He seems to be an exceptional meticulous guy and loves his bees and seems also to be very giving in his information. In a nutshell, he wants to help bees scientifically, as his site says.

  • Rusty, I made up a batch of the towels, was very easy, but what I found is that I left them for 2 days under pressure, found the oxalic had started to crystalise on the paper before I put it on the hives. Will see if that makes any difference, but they moved away from it initially but today were walking over it and seemed to be trying to chew the edges

    Question is, is there a period that the towels can be stored for or should one make them up and put them on the hives pretty quickly , the paper didn’t seem to cover that.

    • Graeme,

      Randy does says the extra liquid can be saved, and somewhere else he talks about crystallization in cold weather (which is generally dry). And in another place he talks about the towels disintegrating if they soak too long. All in all, I think I would just make as many as I could use immediately and save the extra in a jar.

  • Please help opened my double brood yesterday.they have not been taking down the fondant but have a good honey store. Bringing in pollen also. Very worried at affected bees with v.mite damage. Is it too late to treat with OA?and are the towells used the tear off big rolls used for cleaning up in workshops? PlEAseHELp

    • Noreen,

      Have you sampled your bees to do a mite count? That would be the first step. Use a sugar roll or alcohol wash, and then you will know whether or not to treat. The oxalic acid and glycerin method is still experimental and not legally recognized, so another method might be better, especially if you are not experienced. But yes, the towels are the blue tear-off type used for auto repair, etc.

  • Hmmm…if you do not distribute your bee-related products, is use of the paper-towel method “illegal” or is it simply not EPA-approved?

    • Julia,

      I’m not sure how it works. Using some in-hive products, like antibiotics, is just plain illegal because the government is trying to prevent resistant organisms from developing. Oxalic acid is an EPA-approved product, but this method of application if off-label. Probably no one would object unless you tried to sell the product. Supposedly the question at hand is how much OA gets in the food supply. It’s a good question for a lawyer.

  • Hello there Rusty,

    Just discovered Randy’s article last night – it looks promising! Thanks for your great article and being able to condense it all. I’m still not totally clear on how dry the shop towel should be after you press and/or squeeze out 1/2 of the solution. In his photos it appears that his towel are still damp when applied to top bars. Is it also possible to let the shop towels dry out completely or will that decrease their effectiveness?


    • Clark,

      At one point Randy says, “If allowed to air dry, [the towels] will be a little stiff. Once in the hive, they will quickly rehydrate, and the bees will get to work at removing them.”

      • Some feedback on this method, it certainly works and side effect is it seems to kill wax moth larvae which is great for overwintering boxes, BUT

        A lot of Beekeepers here in NZ tried it and found it works well between two brood boxes, single boxes and nucs seem to ignore it and it’s definitely a contact treatment from what we can see .

        It also is not a rapid knock down treatment so hives with high mite loads need to be treated with formic or strips, we have had a number of losses when used as end of season treatment

        View here is that it’s a great maintenance treatment if the mite numbers are not nearing critical stage already, so maybe 3-4 treatments per year vs the current 2.

        Also may be worth using the strip method on nucs and single boxes for hobby Beekeepers who have a bit more time, it seems to work better as the bees are in contact with it a lot more

        • Graeme,

          That’s interesting. I’ve also heard that it wasn’t working well in nucs, but I hadn’t heard anything about singles. I’m planning on trying it on singles, so I will be extra alert to that problem. I wonder if the relative wetness or dryness of the towels has any bearing.

          • If you look at Randy’s update on 12 Feb he seemed to place less onus on the dryness of the towel compared to his initial method, but I treated 12 hives with one batch of fairly dry towels with varying results, I think a single box with honey supers above would work, but seems easy for the bees to ignore if they are not forced to moved up and past it. We have had the worst season in most people’s memory so a lot of hives were fairly weak comparatively which could have been a factor

            Be really interested to see feedback from your readers through a full season.

            Great blog by the way.

            • Thanks, Graeme. I will be sure to pay attention to the singles when I try this, and make sure they have something overhead.

        • Sorry to comment on an ancient post’ but in my view the article is so important and of course reading other beekeepers’ finding on what looks like what Harris Jeubet (I hope I spelled his name right) says as being the possible silver bullet we’ve all been hoping for.

          I put 20 grams of 1 to 1 of oxalic acid and glycerine on a 2″ x 9″ piece of capillary mat 1/8″ thick and the very next day counted 300+ mites dead on the catch sheet which has a thin coat of cooking oil on it. The next day the number had halved and the next day same. Today I lined up 34 mites.

          I have a strong perception that the numbers will eventually be zero because that is the number in the big colony = zero for almost 2 weeks now. It is as Randy Oliver says 2022 report part 1 = very exciting.

          It has been said that the dragging of heels in terms of the legislation is because there is not big money in this idea regarding the strips. The latest Scientific beekeeping through the eyes of a biologist is a must-read for anyone plagued with varroa mites and I would be surprised if it is the done thing to do very soon. Why has the idea not been heralded by a ‘fanfare of trumpets’ =I do not know for the life of me.

  • Thanks Rusty! This is a great article.

    I have a fellow beekeeper, that uses sumac heads, in his smoker. He swears by the method, and then uses oxalic acid, just prior to winter. He is a firm believer in knowing your mite load, FIRST. That gives you a baseline, of where you are, for treatment.

    He has convinced me to sugar shake mine.

    So, now I’m somewhat educated to what my load is. But, I’ll probably give this a shot. Sounds promising. Al

    • Al,

      As I’ve stressed here hundreds of times, treating without knowing your mite load is unconscionable and leads to resistance. Also count first, treat later.

  • The rehydration in hive part made me think it can be applied either damp or dry. Am I correct in assuming this?


  • OOOOhhhh … head is spinning and I failed algebra. Can someone help me out…?….please!!
    If I wanted to do a drip application of Oxalic acid and use a squeeze bottle measurer like the one in the video of Margaret Cowley.
    How much of a percentage of this mixture:

    Measure 600 ml of hot water into a non-reactive container.
    Add 35 grams of oxalic dihydrate crystals (wood bleach) into the hot water. Stir but do not shake.
    When the crystals are dissolved, add the 600 grams of sugar. Stir until dissolved.

    do I give one hive? Does this make 50 mil? Or this mixture more than 50 mil of acid when mixed?
    How much acid of 600 ml of water with 35 grams of crystals….etc. etc. I’m not a scientist but I AM confused.

    • Jeff,

      First, you make up the solution as stated because the proportions come out more accurately than trying to make a smaller amount. Once the solution is made, you measure 50 ml of it into your squeeze bottle or syringe. 50 ml treats one hive. You put about 5 mi of it between each two frames.

      I don’t know exactly how much solution the recipe makes, but since you start with 600 ml of water, you’re going to have at least 600 ml of solution.

  • Randy my friend, you are a God send.
    I was a new apiariest 23 years ago.
    I had many mixed results to say the least,
    from less than accurate advise and
    Information. I knew little, and blogs and the vast offerings
    of the internet were not very accessible to me. In fact there
    was little available on line then compared to now.
    I gave up after a few frustrating years.
    I have since retired and have a very small
    “gentlemans farm”. My recent successes at this have
    encouraged me to try bee keeping again. I knew that access
    to the web would be a total game changer this time It is proving so.
    I give a great deal of the credit to you and your blog. The knowledge
    and Insight of your courageous patrons has also been of help.
    Thank you so much. I feel almost as if I have a mentor.
    Sincerely, Dave

    • George,

      Both alcohols, propylene glycol and vegetable glycerine are commonly used as liquid carriers. But why one is used over another, I don’t know.

    • “VG” means vegetable (plant) source glycerin. “PG” means petroleum (oil) sourced glycerin. Chemically, glycerin is glycerin, regardless of the source it is derived from. “PG” in this context is not propylene glycol.

  • It’s I can get propylene glycol is slightly cost more, but I have access to it, both are basically the same thing, but was wondering if I could us PG. Thanks for the reply.

    • George,

      I don’t know why Randy Oliver chose one over the other, but perhaps there’s a reason. I like to use the things that have been tested.

      • Oxalic acid is more soluble in glycerin (about 500g/kg) than in water, alcohols, propylene glycol, or any other reasonably inexpensive solvent I know of.

  • Hi Rusty,

    Do you know if anyone using this method has reported finding many varroa on the bottom boards in the week/weeks following treatment? Where previously there were few to none?

    Thanks! Adair

    • Adair, et Al, I used OA shop towels to reduce critical mite levels in 3 hives to zero in a period of about 6 weeks. Some hives were slow to remove, lasting two months or more. Excellent results and I am now a firm believer.

  • Hi Adair,

    I know of a couple of local beekeepers who have tried it and had enormous mite drop. (not me…this year) :-).

    • Hi again Julia,

      We have been monitoring our bottom boards and have had huge mite drops weekly! Mostly tiny mites, which tells us that the treatment is working on the newly hatched bees with mites on them. There is also a lot of shredded shop cloth fibers on the bottom, which is how it’s supposed to work, if I understand correctly. We went from none/few mites to what looked almost like black pepper on the bottom board. Some were so small it took a strong magnifying glass to identify them. We hope we are making headway against the varroa, since we lost several hives to them last year. We will be going in to check everyone tomorrow or Friday, depending on the weather in MI.

      Best to everyone!


    • “It is possible in Spanish or French thanks, it seems interesting.” Sorry, but I don’t have the time or energy to do it. I can barely keep up with the English version.

    • Yes, it worked for a time or two then began failing. It’s much too hard to get the OA deep into the hive.

    • Sure. It’s the Everclear part I don’t know about. Is that common and is there something special about Everclear? I thought people were dissolving the OA in water or sugar syrup.

      One of the problems with OA fogging as opposed to the glycerin method is that fogging has to be repeated several times, whereas the towel method is “time-release” and should destroy mites without repeated application.

      • The everclear ( alcohol) and the water are the carriers for the oxalic acid. They both make a vapor ( steam) and carry the oxalic vapor into the hive where the steam condenses on all the cooler surfaces. This deposits the oxalic acid on surfaces where the bees and mites will contact the crystals and mite contact with oxalic is the kill method. Alcohol and water have different boiling temperatures, so I don’t know if there is a difference in effectiveness. It is important to flush the alcohol or oxalic acid from a fogger after usage to prevent corrosion from the acid. I think water will be easier on rubber seals etc than alcohol.

    • I would like to know about the honey supers. Can they be left on the hives when u treat for mites using this method.


      • Frances,

        The official US EPA label for oxalic acid says, “Do not use when honey supers are in place to prevent contamination of marketable honey.”

  • Rusty,

    I believe the Everclear or pure grain alcohol is to slow the vaporization. I’ve heard some beeks use mineral oil.

    • Well, that’s interesting. It would seem that Everclear would speed it up. Alcohol evaporates really fast. I would expect mineral oil to slow it down.

  • I only have one very active hive currently in Southern California. The days are just now getting shorter and cooler. I saw a few mites on the white board every few days and decided to treat using the paper towel /oa/glycerin recipe. Mite counts now in the 100 range four days in a row on the white board now! I’m very impressed.

  • Hi Melissa,

    It’s great to hear that someone else is seeing what we’ve seen. We were in closing our hives down for the winter a week or so ago and the only shop cloth residue was on the tops of the frames. The bees had chewed/carried off most of the rest. I took a FLIR picture of the hives last night and they are in cluster now, assuming the weather doesn’t warm up and cause them to break up. Both our hives had great population and great honey stores to go into the winter. We’ll report back on the flip side.

    Adair and Jerry

  • Just FYI, we have been playing with this method and having come out of winter it seems towels are not effective as hives hunker down, beekeepers that made strips and hung them between the frames found it worked far better through winter.

    The strong summer hives are removing the cloth in less than a week, so not even a full brood cycle, so we are experimenting with cardboard infused strips hung over frames as well, seems to last a good few weeks so will see how effective it is when we do a alcohol wash.

    • HI Graeme, and thanks for the input. Where are you? Here in the upper mid-west, it seems that the strips between the frames would interfere with the bees forming a cluster for the winter….. Your thoughts?


  • Hi Adair, to be fair our winters are probably a lot milder than yours so our clusters aren’t as tight. Our bees will often still have 2 frames of brood, vs what I presume in your case would be minimal and just sufficient to keep the hive numbers viable.

    Because we seem to be getting milder winters and more brood we are seeing increased losses due to varroa so keeping an organic treatment in place over winter has paid dividends in hive build up over spring despite a very wet start.

    The only thing we can say is that the towel method over the top during winter didn’t work, I can only assume that by having it between frames, even emerging bees and mite were exposed to oxalic very quickly and hence what seems to be far healthier hives overall.

    One gentleman is running 3 test hives per treatment method and is saying his alcohol wash on OA/GLY hives showed no mites which is an amazing result for start of summer.

  • I’m so encouraged hearing and seeing the good results from oxalic acid. My husband and I kept backyard bees about 25-30 years ago and had to stop when the Africanized bee scare started. Back then, tracheal and varroa mites were just rearing their ugly heads in Southern California. We just got bees again last year and it was sad to see the lack of progress made in mite control over the years, until I found oa/gly. Every other treatment I found seemed so invasive and hard on the bees, built up in the comb, and led to resistance. I’ve really appreciated the knowledge and support here on HoneyBeeSuite. Thanks, Rusty…and everyone!

  • Hi Rusty,

    There are no commercially sold ready-to-go oxalic pads or something that you would just put on top of the frames to do the trick? This home chemistry sounds quite dangerous to me and I am, well, I even studied chemistry in college unlike most people who would be trying this in their garage.

    Thanks, Jitka

    • Jitka,

      No, there is nothing on the market because, as the post explains, it is not yet an approved method of mite control.

  • Great share Randy and the commentary was also very helpful. We are in the midst of our Canadian winter on the west coast. I have only one brood chamber and a medium super on top converted to a quilt box which is working out wonderful. I was noticing big mite drops on my bottom board over the last few weeks. I went ahead and purchased a vaporizer for OA treatment. The mite drop was quick and lasted several days with close to 150 mites on the sticky board. Couldn’t apply the towel treatment but I’m excited to try this.

    I did a MiteAway Quick strip treatment in mid August after honey supers came off. Thought I was good for mites but obviously had a mite bomb in October as a mite test revealed high numbers. I did the powdered sugar treatment a few times to help and had good drops. This OA treatment was very quick and “mitey deadly”.

    Looking forward to trying the towel method once hive is in brood mode!! Thanks Randy

  • I tried Randy’s shop towel method in the 2017, laying a full towel across the top bars in the center of the lower deep. In some hives it seemed the bees considered this towel the top of the hive and were slow in drawing comb in and utilizing the upper deep, even when there were a few frames of drawn comb placed there. I think Randy’s latest updates on the methods references a similar observation, and that the preferred method currently is to cut the roll of towels in strips and apply the strips with spaces between them, it being easier to work with the smaller strips and I think less likely to impede the bees. I’m going to try this adjustment this year, and also stay away from the center of the brood nest where the bees seem most inclined to move up. I noted in Randy’s most recent update photos of the center of the shop towels eaten away – those photos suggesting a similar interpretation of bees wanting to use the center of the nest.

    Might it be possible to prepare the OA/glycerin mix in a W/W solution, and then weigh the shop towel (or portion thereof) after saturating it with glycerin and squeezing out the excess (subtracting as tare weight the unsaturated towel portion used)? This would allow calculating more precisely the total amount of oxalic acid applied per hive, as squeezing the towels dry leads to total oxalic values within a broad range because of the imprecision of “squeezing.” This would be impractical for high volume field use, but for small time beekeepers like me, help in standardizing dosage and also removing the excess OA/glycerin solution to achieve a more Goldilocks like “dryness” (not too wet, and not too dry) that the bees are most likely to chew on and remove over time.

    I had a bit of trouble hitting the Goldilocks saturation point this year. Some of the towels weren’t chewed at all and I think it was because they were over-saturated. Some of them worked just like Randy’s examples & there were nice little pieces of blue towel outside the hive entrances as the bees removed them gradually. The over-saturated ones got built up with propolis along the frame tops and I wound up cutting through them at first so I could get the frames out to inspect the hives & eventually scraped the pieces off with my hive tool. The bees eventually cleaned off the residue.

    • Keith,

      Thanks for your observations. I’m in process of updating my post to match the new recommendations. I did not have good results with the towels this past year and noticed, like you, that sometimes the towels were chewed nicely and discarded and sometimes they just got propolized in place. I also had very little mite drop, less than I should have based on sugar roll samples. We have to remember it’s still a work in progress, though.

    • You could use drywall shim strips as the carrier. Cut to about an inch longer than your brood frames are tall, soak them, drain to the point of not looking glisteningly wet, insert between the brood frames, bend the top 1″ over the top bar and pop in a staple or thumb tack. Brood will be raised right up to them, sometimes even under them. Queens hide under them. Bees will slowly remove them, slower than the towels, but they can’t avoid them as easily as a towel laid on the top bars. Weigh a dry strip cut to length and compare it to a soaked one. Calculate the dose of OA in a single strip based on your solution’s concentration and the absorbed weight. Maggi’s study, easily found online, used about 40g of OA per brood box. This works; just don’t ask how I know.

  • Cal:
    Can you clarify “drywall shim strips?” Do you mean pieces of drywall cut into strips? If so, is it 3/8″ drywall or 1/2″? I’m suspecting 5/8″ would be too thick. Also, is there a recommended width for the strips – you’ve been clear on the length – somewhere close to 10 1/2″. Or are “drywall shim strips” a unique product I’m not familiar with? Pieces of drywall cut and soaked in the manner you describe would be very easy to prepare, store, and use, and I think much more practical when it comes to standardizing the dosage per hive.

    In Randy’s first articles on the shop towel method he mentioned using egg carton cardboard as a carrier, mounted over the frames much like you’re describing above. As I recall, this was effective in treating for mites, but his son (was that you, Rusty? I’m sorry if I’m wrong on your identity, as I’m a late comer to this posting) nixed the idea as it’s too time consuming placing the number of strips required and then removing them later. If the bees remove the drywall, that would seem to resolve that issue. I think drywall is currently treated to prevent certain types of mold growth, so there’s another thing to consider & maybe someone reading this knows more & can comment.

    • Keith,
      Drywall shim strips are used to correct the plane of a wall before putting on the sheets of drywall, by stapling them on the wall studs to fill in a low spot. They’re unbleached paper cardboard, similar to what you see egg cartons and cereal/cracker boxes made of. You should be able to find them at any place selling drywall products. A 100-pack of shims was going for about $11 at a big-box home improvement store near me. The shims are 1.5″ wide, 45″ long, and 1/16″ thick. The product’s packaging and the manufacturer’s literature make no mention of having any mold-inhibitors in it.

  • Rusty – 3-days ago I picked up a package of bees shipped from NZ and installed them. As I understand bees sent internationally are treated prior to shipment. At the time of installation I had a mite board in place but did not expect to see mites from the installation. After cleaning the board – without looking for mites! I noticed spots which turned out to be mites stuck to the board. Now, two days later I have a mite count of 136. The package came with a single strip – this I’m told is good for 42-days – not sure the product but looks innocuous – white plastic no odour. I’m told it works by bees walking over it. I’ll continue monitoring everyday. If numbers remain this high I’m thinking of doing an Oxalic vaporizing treatment at the end of the week before our first capped brood appears (queen is out today). Or best to wait, give the strip (a single one – 1.5″ x 5″) time to continue working. I’m paranoid after having lost two very nice hives last fall to mites.

    • Vince,

      Not sure. I guess my question is this: Were the mites all dead? If so, maybe the strip is working and the mites are falling off the way the are supposed to. It sounds like the white strip might be Apivar, and there is a lot of resistance to Apivar, so maybe an oxalic treatment would be warranted. Judgement call.

  • R –

    One mite was kicking legs, but another 16 were counted on the very outside edge of the gridded testing paper (stuck in place to help assist in the counting). My thoughts were for them to be there some likely crawled but just a guess. I never lost a queen last year to the vaporizing treatments we administered, nor saw any abnormal number of dead adult bees immediately after treatments, but that’s my concern.

    Last year the first mites I saw came in June and just 2-3 when first noticed. I’m sure you are right about the treatment having the effect intended and the large number being dead from it. I was told the bees were treated prior to shipment and the strip put in to maintain some form of longer term control. I’ll wait, and see how the daily count goes. If a precipitous decline over the next week I may hold off but sure tempted to do one OA treatment before capping of brood. It would be a risk, but so is an uncontrolled early build-up of mites. The above discussions on using OA as a long-term treatment option are valuable and may provide a good alternative to vaporizing now – given our queen is new and hopefully working on building brood. However, this is the only brood-break I will have until I can split the colony later in the season. So tempting to make use of it.

  • Rusty, thank you for all of this good information. I’m in Colorado, lost both of my top bar colonies last fall to mites. I’ve used sublimated OA in Langstroths (lost those colonies to mites too, probably too little too late); but I REALLY dislike doing it that way. I’m getting two new packages next week, and I’m going to give the shop towel OA/glycerin method a try, but I’m not sure about timing and placement with a new package in a top bar hive. I think using strips of towel (or dry wall shims? – I’ll have to check that out) hung vertically from the top bar between brood combs might be the way to go, rather than full sheets. Do you have any new insights specific to top bar hives?

    • Go with what Maggi, showed worked in their study – strips. You may want to remove them after a suitable period but you only have 2 hives, not the hundreds or thousands a commercial beekeeper does, so that is no big chore for you.

  • The person whining about the potential danger of making the solution is a bit of an alarmist.

    Making homemade soap is far more dangerous than warming glycerine and dissolving oxalic acid in it.

  • Hello all –
    So after reading the paper, Rusty’s article, and all of the posts, I think that doing the cardboard strips on my hives (I only have 4) and then just removing them after two months would be best. My plan (I think) is to do Apivar strips in the Spring and then oxalic acid in the late summer and late fall. I’m new at this so does that sound like a good plan? And second, I couldn’t quite figure out the “recipe” for the cardboard strips – can you help?

  • To add into several of the discussions:

    I find if I tear the towel in half and leave a 3/4 to 1 inch gap in between the 2 half’s of the towel the bees go thru the space better and are more prone to start removal. I find a smaller hives where I nader and place the towel in between or super and place the towel in between the bees tend to propolize it and leave it there. If some one tries the draping on singles, let us know how it works. The article I read talked about 37 grams for the “dry” towel weight. I bought the gram scale and did the squeeze and weigh a few times. For me its about all you can squeeze out to get it down to 37 grams, practice with several and get the feel and go for it. BTW IMO the final weigh is the “dose” not the wetness, at 25 grams per 25 ml and the towel weight the total is what gets the hive dose right. I do the towel in the spring about 3 weeks before I super , then when supering scrape off the remainder, add supers. In the fall after removing honey then treat again. I warm my glycerine in a glass 2 quart pot on the stove on low, dump in the OA and stir with a paint stirrer or wood stick of some sort, until dissolved. Since I Can cook, I know to not boil it just warm it. if you are stove challenged then do the crock pot double boiler mentioned in this thread. I have a Tupperware type container with the towels in already and dump the mix on it warm. put in the car go to the apairy, then Squeeze the towel, tear in 1/2 place in between the 2 brood boxes. Once you do it a few times it is not to complicated. do wear the nitrile gloves. Scrapping off the propolized towel 3 weeks later will still take the paint off your hive tool. I have seen new packages come with mites, i would treat some how or they will collapse in the fall. Pick your posion, and read the MSDS and follow the warnings. The OA/GLY does not work by vapor it works by contact. If someone has more tips please let us know.


  • Rusty – just researching the OA towel method. So far no need to treat but I want to think about how this treatment can be best used if needed. For example, there is a delay time in the wet towel OA treatment to work. Have you heard of anyone using OA vapourizing for an initial treatment for killing phoretic mites then adding the towel method to work-longer term. This would be a combination treatment of using OA vaporizing along with the wet towel treatment to provide control over the longer term. This would eliminate the need for consecutive OA vapourizing treatments. Such an approach being applied now – mid-August if mite counts show need for treatment. OA is very easy on bees and queens making it an attractive treatment.

  • Hi, I know this is an old article, so I don’t know if anyone will see this question, I’m having a hard time getting on to scientific I have an 8 frame observation hive that now (Sept 13 2018) just swarmed (7 days ago) has a good amount of uncapped and capped brood and I am seeing a few visible mites (3-4) on my bees. The other workers are trying to help the itchy bees out and grooming them, and I’m not seeing mites at the bottom of the hive, nor any deformed wing. But, I am still waiting for a queen to emerge, AND I am not sure how best to vaporize the hive. Getting into it involves taking it off the wall and going outside with it, as well as opening up one whole side. Vaporizing possibly could be done through one of the ventilation ports, but not easily, so this article seems to be a godsend, because I could easily put a OA/glycerin towel into the hive. My question is this: do I need to wait until the queen is laying before I do this? It’s mid September now and I don’t know if I can wait that long with visible mites in my hive. I’ve lost 2 observation hives to mites in the past. Also, does this method bother capped or uncapped brood? By the article, it doesn’t seem to, but I’m unsure. I know that most of this brood is likely to be winter bees and I’m worried that they are going to be damaged by mites before they’re even emerged.

    I am located in NY State, and the bee hive itself is located inside all year long, so I don’t need to worry too much about cold. I would be interested to try this method on my hive and would happily provide pictures/information for anyone interested in seeing how it works in an observation hive. My thought is that I would cut the paper towel into stops to lay across the tops of each 2 frame set. Any suggestions, advice would be appreciated. Thank you

    • Sasha,

      Here in the states, this method is not yet approved. I think you would be better off by using a strip of something like HopGuard or Apilife Var. You could cut the dose down to serve the number of frames you have. Most of the mites are under the capped cells, so seeing mites on bees is a bad sign.

  • I want to know if someone use strips from auto air filter for support innstead of paper.

  • Rusty, thank you for your good work and efforts on helping disseminate this info. Am I the only one who is alarmed by blue shop towels turning the OA solution blue? Just doesn’t sound organic or even healthy to me.

  • Rusty, I really appreciate your blog. I have done both methods and I cannot say that I felt nearly as confident about the shop cloth method as I do about my vaporizer. Stirring up chemicals and hoping I measured correctly is not less scary than using a well-designed vaporizer that is not going to catch my hive on fire. But, my question is, what about Jennifer Berry saying that mites cannot become immune to oxalic acid any more than we can become immune to being hit with a hammer (paraphrased for convenience)??

  • I use a curling iron that I bought at goodwill for $3.00 to heat 3 grams of oxalic acid powder. It turns to a gas in 2.5 minutes and completes the oxidation fumes at 12 minutes. I have a video of the process and the temperature stats. The iron goes to 400 degrees on turbo mode. Florida business has 5lb OA for $12.00 on amazon.

  • Rusty, would this be an effective treatment in late October-early November when daytime temps are 50-55*f?

  • Where is the research showing that mites have become resistant to oxalic acid?

  • Thanks for posting this info, Rusty! I had been reading over this info on Randy’s site. The “recipe” was very easy, and I just happened to gave glycerine! I have a top bar hive. I saturated the towel with the 25/25 g/ml mixture. I weighed all on my scale. I just squeezed between newspaper until I had half the starting weight. I hung my towel in the brood area between two top bars like a curtain. Hopefully, they will remove instead of just walking around or under it.

    Thnx again!!

  • I’m fighting varroa now, may 2021, and it’s a heavy infestation. Bees are pulling out larvae and seeing some crawlers. The hive is very strong, 20 bars of bees, and that’s with sharing 3 brood combs. I’m afraid of vaporizing, plus they’re too spendy. I did a dribble today and have the ingredients for a shop towel. My thinking is hanging a towel between two bars, would’ve like a shower curtain, with the bees just going around it or to side of it. I’m thinking maybe I could put on floor under the comb?? Would that be too much contact?

    • Melissa,

      The shop towel method is not approved by the EPA so I cannot give advice about it.

    • M, maybe you can try cutting the shop towels into 4 strips and draping those over the frames. If you did that and you find blue fuzz on the bottom board, I bet it will work. But if that hive is different, they might propolize the strips and then have no effective release. “Just thinking”.

  • Hi Rusty, this article about using OA/Glycerin shop towel treatments for verroa sure generated a lot of comments back in 2016. I understand that until/if this method is approved by our EPA you can’t comment on it but do you know of anything currently in in print elsewhere you can refer us to that says anything new about the efficacy results from this method?

  • Although I liked reading this, if it is still illegal in the US, I think you should remove the instructions on how to do it. A person posted a link to this on a Facebook page, saying they are going to do this.

    What risks are there if this illegal process is used in honey bee hives?

    • Mark,

      Although it’s been eroded over the years, here in the U.S. we still have the first amendment right to freedom of speech. Talking or writing about something is different from doing it. So no, I won’t remove it.

      The risk is the potential contamination of a human food product. The studies necessary to answer the questions are very expensive. Unless a company sees a way to make lots of money from it, no one is going to finance the studies.

      • Thanking God (if I may still use His name) for patriots like you. I’m going to whip up a batch in your honor. My preference is using the Swedish sponges – available once again online at an unnamed massive liberal leaning company with quick shipping.

  • Rusty, in NZ we are using strips of materials hung over or between the frames, shop towel gets stripped out too fast, but most of us are seeing great results with these with low or no mite loads

  • In British Columbia, Canada OA is widely used for mite mitigation. It is legal and sold commercially. It is recommended primarily as a treatment in spring and winter when hives are broodless and mites phoretic.

  • Good method. Only issues might be heat causing evap or liquification in the hive and possible interaction with certain dyes used to color the towel. But easily solveable, apply august for brood that will care for hive during winter and use undyed towels.

  • Hello — I am in south central PA and wondered if you had advice on the timing of OA pads (OA + glycerin on Swedish sponges). I put some on my colonies last fall and left them on all winter. I replaced them in April. My colonies survived the winter well and have had a good summer with only 1 or 2 mites each colony. I’m planning to replace the pads soon with fresh pads (OA + glycerin) but wonder if I need to introduce a break during which there is no OA treatment?

    • Hi Pam,

      I cannot answer your question simply because the EPA does not recognize oxalic acid and glycerin on sponges as an acceptable treatment protocol for varroa mites in honey bees. As you know, the label is the law and I do not advocate for off-label use.

      Also, the label specifically mentions resistance management. Regardless of the method you use, OA should be rotated with other treatment methods. Since OA does not kill mites beneath cappings, times of high brood rearing are excellent times to use a different product. From the label: “When possible, rotate the use of miticides to reduce selection pressure as compared to repeatedly using the same product, mode or action or chemical class. If multiple applications are required, use a different mode of action each time before returning to a previously used one.”

  • Planning to try shop towel method as soon as I take off honey supers ( late September in upstate NY where late flow is productive). Daytime temps can fluctuate 50s-80s, nighttime 30s-50s. Too cold for this method?

    • Victor,

      It will most likely be fine. The temperatures in the brood nest are held steady by the bees, and since the towels are close to the top of the nest, they will be warmed by the bees.

  • Rusty and others like Victor: I’ve been at this mite thing now for quite some time. Needless to say, it is not easy to control mites regardless of the method. Personally nothing in my data suggests any method gets mites to zero. Far from it. Victor – your September 18 – post. This is far too late in the season to get the results you want. Your mites, if you have them and you most likely do, are running around as phoretic mites and inside cells doing their damage. All you can do now is hope for the best.

    I have made all the same mistakes and paid the price. Last year, I went with Amatraz on September 2. I wanted to start the first week of August but had to be away. Amatraz killed thousands of mites but it does not get under caps where the damage lies. I even hammered them with OA vapor after Amatraz and still had hundreds of mites show up. DWV, Nosema, and other hazards took their toll on several hives and weakened others.

    A year earlier we lost on the order of 70% of hives regionally. Even those of the best, most experienced keepers. This year I began working with queen exclusion traps. 4-hives in the trial. Queens were excluded on July 21. The purpose was to trap phoretic mites to extinction! Of course, you can’t! But the traps did capture thousands of mites – all through July and most of August. The hives went broodless which allowed me to use OA vapour to “clean” the remaining mites. I got enough mites in 2-OA treatments to show even trapping to broodless can not get to zero.

    On 21 July I began OA extended in non-trapped hives. That treatment takes time. You don’t get the drops you see with vapour. This of course means you have to go through x number of brood cycles to get most of the mites. Thus, anyone starting any such treatment in September has to accept they are late and well past the time needed for good control. I uncap drone cells from frames laid up by excluded queens. Average mite counts in those cells times the area of cells give me a kill count. This goes to thousands over the trapping periods. These are all mites that would have entered winter bee cells. I can easily 50% of winter mites would have been infested had I not trapped. You have to deal with mites in late July and no later than early August. Otherwise, hope for the best.

  • OA binds the CA- ions which form a basis of mite biological communication. Without free CA ions, they can’t taste or move to a cell.

    The same thing it does to soft-bodied insects eating spinach leaves or causing gout in humans.

  • Daniel – what’s the point your making. Sorry but I don’t understand. “Mite communication” are you suggesting OA disrupts the ability of mites to eat or find their way into a cell just before it is capped? How does this explain mite drops that are usually greatest on Day 1 of post-treatment followed by a reduction in numbers usually to Day 3 and few to Day 5? That suggests the decline is due to mortality or inability to cling to a bee due to lack of function. Mites on my mite boards are nearly all dead or paralyzed. Some are still kicking and a few fast enough to scurry away when poked.

  • Sorry, I meant kidney stones overall; approx 5% of all stones are mixed calcium oxalate and uric acid.

  • Daniel, I am very curious about your background and if there is any of this published anywhere. Could you point the way? I have not yet heard of any conclusive research concerning the modus operandi between OAE and mite fatality and would like to read the sourcework. There are many theories out there; researched & cited statements are much more helpful. Thank you in advance, Daniel!

    You also wrote (above, as a reply to a 2017 comment),
    [DW July 29, 2022, at 10:59 am]

    “We know the mode and PH is not a factor. Oxalic acid well known effect is that it reduces (oxidizes) calcium (and other metals), mites have/need free calcium on their mouth and feet as it is used in chemical communication (taste & movement). The reduction of that free calcium ( the same reason some people shouldn’t eat spinach) binds Ca into CaO and releases a lot of localized heat. Both effects interfere with the mites’ ability to move and locate feed. The Ca in a bees exoskeleton is bonded in chitin so the OA has little effect on honey bees unless they consume it.”

    • Daniel,

      I agree with CiCi. Please provide sources and credentials. Your theory doesn’t comport with any research I’ve read.