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Oxalic acid and glycerin for varroa mites

For beekeepers who treat for varroa mites, oxalic acid has become the default favorite miticide. It is inexpensive, a natural component of honey, safe for bees when used as directed, and is 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 is often used 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 beekeeper, 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

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 are killed 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 not 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 would be 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
  • A 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 the shop towels were prepared

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. Chemical-resistant gloves and protective goggles are needed when using oxalic acid.
  2. He used 25 ml of glycerin, 25 grams of oxalic acid, and one shop towel for every hive.
  3. The shop towels were stacked in a plastic tray.
  4. The glycerin was heated in the microwave until it was hot but not boiling (about the temperature of a cup of coffee).
  5. He stirred the oxalic acid into the warm glycerin, mixing thoroughly.
  6. The warm mixture was poured over the towels in the tray.
  7. Once the towels were saturated, he removed them to the second tray to drain. Randy 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. The remaining liquid can be stored in a glass jar for later use. Randy warns that the liquid became quite blue.

Once the towels were prepared, he 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.

Rusty
Honey Bee Suite

Varroa mite
Varroa mite. Pixabay photo.

Note: this post contains affiliate links.

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Comments

Oliver
Reply

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.

Rusty
Reply

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.

Wei
Reply

I wonder if perhaps this method could be used when the honey supers are still on then perhaps?

Rusty
Reply

Wei,

I doubt that warning will change unless someone is willing to pay for studies.

Carol
Reply

Rusty, this is fantastic! Thank you for sharing it. I will definitely read Randy’s write-up.

Laura Colburn
Reply

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

Rusty
Reply

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.

frances I Moore
Reply

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

Rusty
Reply

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.

frances I Moore
Reply

Thanks for everything, u are great, keep the post coming I so much enjoy them.

dave hortin
Reply

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…

Wei
Reply

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.

Rusty
Reply

Dave,

Wei is correct on this and makes some good points.

Paul
Reply

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.

Dan Stoffel
Reply

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.
Thanks,

D. Dtoffel

Rusty
Reply

Dan,

(Mr.) Randy used one towel per two chambered colony and he put the towel between the two chambers.

Graeme
Reply

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 http://www.supercheapauto.co.nz/Product/SCA-Shop-Towels-200-Pack/376538, should work ?

Rusty
Reply

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.

debbie
Reply

WOW … what a brilliant idea ! Thanks for sharing.

Cathy Wilde
Reply

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.

Rusty
Reply

Thanks, Cathy.

Mark
Reply

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

Rusty
Reply

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.

Cathy
Reply

Thank you
I’m trying this
Lost my hives the last 2 years in the fall from mites

David
Reply

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?

Rusty
Reply

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.

Tom Mckinney
Reply

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

Fred
Reply

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

Rusty
Reply

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 🙂

daniel weston
Reply

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.

Shawn Bird
Reply

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.

jim
Reply

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

Jim
Reply

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!

Cal
Reply

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.

Oliver
Reply

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.

Oliver
Reply

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.

Rusty
Reply

Oliver,

Did you read Randy’s article? I think not.

Oliver
Reply

Sure, and we use and study this method for years.

Mary Keogh
Reply

Ìs OA safe for the bees to eat as they chew on the paper towel?

Rusty
Reply

Mary,

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

Bob
Reply

Hi Rusty,

I may have overlooked it but does this method discuss the application in a top bar?

Rusty
Reply

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.

Bob
Reply

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?

Rusty
Reply

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.

Oliver
Reply

No vapor, cause here we use oxalic, not formic acid. To vaporize oxalic acid you need a heat source.

Dawn
Reply

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.

Bob
Reply

And by the way u r funny.

Graeme
Reply

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.

Rusty
Reply

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.

noreen
Reply

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

Rusty
Reply

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.

Julia
Reply

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?

Rusty
Reply

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.

Clark
Reply

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?

Thanks,

Rusty
Reply

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.”

Graeme
Reply

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

Rusty
Reply

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.

Graeme

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.

Rusty

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

Al
Reply

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

Rusty
Reply

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.

Clark
Reply

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

Clark

Rusty
Reply

Clark,

Yes. I believe that is correct.

Jeff
Reply

OOOOhhhh …..my 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.

Rusty
Reply

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.

Dave Hoffmann
Reply

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

Stuart Herrmann
Reply

Great article.

George Anderson
Reply

What would be the difference between VG or PG as a base ?

Rusty
Reply

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.

Cal
Reply

“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.

George Anderson
Reply

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.

Rusty
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.

Cal
Reply

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.

Adair Renning
Reply

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

Rusty
Reply

Adair,

Personally, I don’t know of anyone using it.

Chuck
Reply

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.

Julia Youngs (Machias, WA)
Reply

Hi Adair,

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

Adair Renning
Reply

Thanks so much for that information Julia!!!

Adair

Adair Renning
Reply

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!

Adair

jesus serrano valles
Reply

es posible en español o frances gracias, parece interesante

Rusty
Reply

“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.

Dickydoo
Reply

Randy

Have you ever used the Insect Fogger method using everclear and oxalic acid?

Rusty
Reply

If you are asking me (?), no. I’ve never heard of using Everclear with OA for fogging.

Chuck
Reply

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

Dickydoo
Reply

Can I give you a few youtube sites that are using it and then get your opinion?

Rusty
Reply

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.

Chuck
Reply

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.

Rusty
Reply

Thank you, Chuck. Good information.

frances I Moore
Reply

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

Thanks

Rusty
Reply

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.”

Dickydoo
Reply

Rusty,

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

Rusty
Reply

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.

Dickydoo
Reply

Yes. I misspoke the Everclear would indeed speed up the vaporization.

Melissa
Reply

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.

Adair Renning
Reply

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

Graeme
Reply

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.

Rusty
Reply

Graeme,

Good to know, and it makes sense.

Adair Renning
Reply

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?

Adair

Graeme
Reply

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.

Melissa
Reply

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!

Jitka
Reply

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

Rusty
Reply

Jitka,

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

Nate
Reply

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

Keith the former lab tech
Reply

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.

Rusty
Reply

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.

Cal
Reply

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.

Keith the former lab tech
Reply

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.

Cal
Reply

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.

Vince Poulin
Reply

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.

Rusty
Reply

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.

Vince Poulin
Reply

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.

Chris
Reply

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?

Rusty
Reply

Chris,

No, I don’t have anything on using the technique with top-bar hives.

Cal
Reply

Go with what Maggi, et.al. 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.

Tsu Dho Nimh
Reply

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.

Donna
Reply

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?
Thanks!
Donna

Keith
Reply

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.

thanks
Keith

Sasha Boucher
Reply

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 beekeeping.com. 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

Rusty
Reply

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.

Chuck
Reply

Use the OA shop towels. Much safer for you and the bees.

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