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How to apply an oxalic acid dribble

Oxalic acid as a Varroa treatment first caught my attention two years ago when beekeeper Mark Luterra showed me a photo of his bottom tray after treatment. What an incredible display of dead bodies! I was intrigued.

Later, I followed up with some research, mainly from Randy at ScientificBeekeeping.com. From him I devised a treatment plan that is simple, inexpensive, and works well.

But first, what is oxalic acid? Basically it is an organic (carbon-containing) compound that is found in nature. A number of foods we eat are rich with oxalic acid, including spinach, swiss chard, rhubarb, beet greens, kale, sorrel, and chocolate. In fact, there is much speculation that the “spinach effect”—that weird mouth feeling some people get after eating spinach—is actually caused by oxalic acid. And we’ve all heard that rhubarb leaves are poison. The reason? Oxalic acid.

Since oxalic acid is found in nature, and because it is a normal component of honey, oxalic acid is considered a “natural” treatment. In fact, even Certified Naturally Grown beekeeping allows the use of oxalic acid for the treatment of Varroa. Oxalic acid is commonly sold as “wood bleach” and can be found in hardware and paint stores. The type I use can be found here: Savogran 10501 Wood Bleach.

However, oxalic acid in the form that works to kill mites is a potent acid, so care must be taken to avoid causing harm to your bees and yourself if you decide to use it. You should begin by reading the new draft label so you know how to handle the acid and how to protect yourself from splashes and spills.

Supplies

Oxalic acid can be applied as a dribble, a spray, or a vapor. Since I am a hobby beekeeper with a small number of hives, I prefer the dribble. Personally, I don’t want to buy, clean, or store vaporizers or sprayers, so I’m happy with a box of disposable syringes that I bought online for the purpose. The KISS method works for me, especially in this case.

If you use the oxalic acid dribble method, you will need a canister of wood bleach, a syringe that holds at least 50 ml, a small scale that can measure in grams (tenths or hundredths of grams is best), a standard measuring cup, sugar, and a non-reactive container for mixing. Your wood bleach should be between 95 and 100 percent pure. If you don’t know, you can search the web for the MSDS (Material Safety Data Sheet) for your particular brand and it will tell you.

The other item you will need is soft water. Soft water is an excellent solvent, but when the water is filled with hardness minerals (chiefly calcium and magnesium) it tends to form deposits or precipitates instead of dissolving things. If you see a white substance in the bottom of your container after you mix in the oxalic acid, you should toss that batch and try a different source of water. If you don’t have a water softener, you can use distilled, deionized, reverse osmosis, or even rain water.

According to the new EPA label, you need to mix 35 grams of oxalic acid dihydrate crystals into one liter of 1:1 syrup. (This is the same as Randy Oliver’s weak solution, and the one I’ve been using.) You can make a liter of syrup by using 600 ml of water and 600 grams of table sugar.

Time of application

  1. Because oxalic acid will not kill Varroa in capped brood, I like to apply oxalic acid at times when little or no brood is present but before it is crazy cold outside. For me, this is late fall.
  2. Treating once per year at the right time may be enough because this system knocks Varroa down to almost nothing.

Prepare solution

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

Apply the solution

  1. Smoke your bees down between the frames.
  2. Dip the end of your syringe into the medicated syrup and pull back the plunger, filling the syringe to the 50 ml mark.
  3. Starting at one end of the frames, dribble 5 ml of the solution along a seam that contains bees. (I like to start at the far end and dribble toward me.)
  4. Once you have dribbled 5 ml, you must go on to a new seam. (A seam is the space between two frames or the space between a frame and a sidewall.)
  5. After each seam of bees gets 5 ml of solution, you are done.
  6. In any case, you cannot go over 50 ml per colony. If the hive has more than 10 seams, dribble where the most bees are. Alternately, you can give less than 5 ml per seam and do more than 10 seams, but you cannot go over 5 ml in any one seam or 50 ml total per colony.
  7. Remember to apply the mixture directly onto the bees. Mixture that lands on the woodenware will be ignored by the bees and not moved throughout the colony.

Dribble practice

I strongly suggest that you practice dribbling with plain syrup in advance. The first time I did a test, I squirt syrup half way across the room. Seriously, it takes a little skill to get the hang of moving the syringe along the seam while gently pressing the plunger. Also, practice reading the graduations. My syringes are marked 10, 20, 30 and so on with five divisions between each one, so five ml is 2.5 divisions. I use this type of syringe: Syringe 60cc Luer Lock Tip Sterile (Pack of 10).

Be sure to use 1:1 syrup for your trial runs because plain water behaves differently. I also recommend putting 5 ml (1 teaspoon) of syrup in a dish so you can see what it looks like.

Once you get a feel for it, you will find that moving quickly along the seam is easier than moving slowly. Also, watching the drip end seems to be easier than watching the graduations once you learn how fast it comes out. Five ml doesn’t seem like much when it’s whiskey, but this stuff is different.

So there you have my method. If you want to use a vaporizer or sprayer, I strongly suggest you read the label and Randy’s site for the best information.

Rusty
HoneyBeeSuite

"CSIRO ScienceImage 7306 A European honey bee prepupa with varroa mites" by CSIRO. Licensed under CC BY 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:CSIRO_ScienceImage_7306_A_European_honey_bee_prepupa_with_varroa_mites.jpg#/media/File:CSIRO_ScienceImage_7306_A_European_honey_bee_prepupa_with_varroa_mites.jpg
“CSIRO ScienceImage 7306 A European honey bee prepupa with varroa mites” by CSIRO. Licensed under CC BY 3.0 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:CSIRO_ScienceImage_7306_A_European_honey_bee_prepupa_with_varroa_mites.jpg

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Comments

DaveS
Reply

I’m not sure what you mean by the “seam”. Can you explain please?

Thanks,

DaveS

Rusty
Reply

Dave,

Thanks. I amended the text to include: A seam is the space between two frames or the space between a frame and a sidewall.

Andrew
Reply

I find using a syringe with a catheter tip works best, little chance of squirting a the bees off the comb.

In the Netherlands we apply oxalic acid on a cold day just after the winter solstice. Then there is the least chance that there will be any closed brood. Any closed brood in that weather will be packed with Varroa.

The Wageningen University has a research group dedicated to bee research, they have published a kind of best practice manual for Varroa treatments. I’ll see if they have a English version and post the link here.

Rusty
Reply

Thanks, Andrew.

Diana
Reply

Back to the “seam” again (still flummoxed, sorry)…are you dribbling solution down the side of each frame? Mine would miss everything and hit the bottom screen which might defeat the purpose! Should I close up the hive?
This is fascinating. Thank you.

Rusty
Reply

Diana,

You don’t take the frames out of the brood box. You smoke the bees and they go down into the hive. Then you drip the solution in the spaces between the frames where the bees are. Seam is a word that they use like a seam of gold or a seam of coal, only this time the bees are the “gold.”

Where are your bees that they wouldn’t get dribbled on? Remember, it’s winter and they’re not out foraging.

Shreve
Reply

Stupid question time…. why use sugar in the mixture? Is it so it sticks to the bees better?

Rusty
Reply

Shreve,

The syrup dilutes and distributes the oxalic acid better than water would. Water would evaporate too quickly, before it got spread around from bee to bee. I don’t know if the researchers tried anything else, but syrup seems to be a logical answer. It’s actually a good question.

dave
Reply

So, in essence, the acid kills mites it comes in contact with without harming bees or brood?

Rusty
Reply

Dave,

The mites are much more sensitive to the acid than the bees. Don’t quote me on this, but I think I read the mites are about 100 times more sensitive (I have to look it up again). However, the oxalic acid can harm or kill the open bee brood, so there is more than one reason for doing the treatment when there is very little brood present.

Charlie
Reply

Hi,
This is my first time commenting and I hope I’m not out of line. I have a bit of concern about the timing of control. Randy through you and others I have come to learn the most important time for mite knock down is before winter brood rearing. In my area lets say Mid- Aug. I’ve been using one application of Formic Jell ( also organic but no fun to work with) with fantastic results.
Do you think I should switch to oxy and could it be applied late summer when brood is low? And also is it safer for the bees and us?
Love all you do here to help us. Thanks, Charlie

Rusty
Reply

Charlie,

One of the big problems with any mite treatment is that the mites can become resistant. Once they become resistant to a product, the product is no good. So no matter which one you use—formic, thymol, hops, oxalic—you should rotate between them. I usually use one product two years in a row, and then I switch to another.

I don’t think oxalic is better than formic, but it is an alternative. So after you use formic for a year or two, you should use something else for a year or two. At that point, you can go back to formic or go to a third product.

My personal favorite time for mite treatments is mid to late August before the winter bees are hatched. But I don’t do that with oxalic. Instead I wait until later, like November or December. If I’m using hops or thymol or formic, I do it in August. The primary reason is that oxalic (I believe) is harder on open brood than these other preparations. On the other hand, these other preparations take three to four weeks, whereas with oxalic I do one treatment and I’m done for the year.

As for safety, I think all these things require caution and careful attention to detail. I’m careful with all of them.

I don’t know if I answered your questions. Give a holler if you need more.

Marsha Bezold
Reply

I do 8 frame, all medium boxes. Would I still use 50ml per colony or less? I am so happy that this is now legally available!

Rusty
Reply

Marsha,

The label says to use a maximum of 50 ml whether the bees are in nucs, single brood boxes, or doubles, so I would assume the same holds for 8-frame mediums. In other words, just think 50 ml per colony.

Andrew
Reply

In the Netherlands we just use 5 ml per seam of bees, if the bees do not occupy that seam then don’t apply the acid. Last time I used the oxalic the colony I was treating wasn’t that large so I ended using using just 25 ml.

If there are just 4 seams of bees then bumping 12.5 ml of oxalic acid syrup mix in each seam isn’t advisable…

Jeremy
Reply

Thanks Rusty! I have been looking forward to this being approved by the Feds. I will be trying it this fall. And thank you for keeping this blog up to date, I really enjoy reading your opinions and fact based posts.

Rusty
Reply

Thanks, Jeremy.

TravisB
Reply

You might try “slip tip” syringes instead of the luer lock, would certainly be easier to draw up the mix with and most likely be better for dripping.

Rusty
Reply

Travis,

Thanks. I’ve never learned so much about syringes in my life. I don’t have any trouble filling the syringes but I would like to have more control on the drip side.

Erik
Reply

Thank you for the post, Rusty. I am still confused with an 8 frame hive. If you shouldn’t put more than 5 ml per seam then how do you use up 50 ml? Even more so for a nuc. After you dribble 5 ml per seam do you just stop? Or do you continue dribbling until all 50 ml is gone somehow? Thank you again.

Rusty
Reply

Erik,

After you do five ml per seam, you stop and throw the rest away.

Emily
Reply

I buy my solution ready made up, no mixing required, e.g. http://www.thorne.co.uk/health-and-feeding/varroa/oxalic-based?product_id=5060. It’s good to warm it a little in a pocket or airing cupboard before drizzling over the bees.

I usually do mine in late December, as close to the winter solstice as possible, as there is evidence that the queen slows down her laying as the days get shorter and starts to increase when the days get longer.

In the UK some beekeepers have lost queens after treating with both MAQs and oxalic acid (several months apart). Some say using both treatments is fine and others think it’s best avoided.

Andrew Millar
Reply

There is a second way to use oxalic acid when combating Varroa, which is in use in Europe. This technique is combined with a certain type of artificial swarm creation. You make a broodless artificial swarm and in transition to the new hive (with only foundation) you spray the swarm with oxalic acid syrup solution. Varroa has nowhere to hide in this technique and you are sure to eliminate very close to 100% of them.

I think you put the oxalic acid in syrup so the bees ingest the oxalic acid, and as the Varroa drinks from the bees hemolymph which now contains oxalic acid which it can’t handle. Similar to the drops you will drip in the back of the neck of your cat. Just a hypothesis, yours seems at least as likely.

(btw. I couldn’t find an English version of the Varroa treatment guide. I now asked someone at the university directly.)

Rusty
Reply

Andrew,

Related to the artificial swarm, you can also spray packages with oxalic syrup. If I recall, you folks in Europe are not so into packages, but a lot are sold over here. It’s a good time to treat because like you say, there is no brood and nowhere to hide.

Gayle
Reply

Do I understand correctly that treating a newly installed package would be a good idea, or even spraying them before, or as, you install them in a hive? Since it’s just about package time here, this interests me. Thank you!

Rusty
Reply

Gayle,

I have never treated new packages myself but I know of more and more beekeepers who do. For example, an employee of the Oregon State University Bee Lab told me they are now routinely treating new bulk bee packages because they have found high mites loads in prior shipments. I haven’t purchased any packages in several years, but if I did, I would probably treat.

David C.
Reply

I use a 50 ml horse syringe I bought from Tractor Supply. You can set the dosage to 5 ml per trigger pull and get easy accurate dosing each time. When the syringe is empty, you are done.

Rusty
Reply

David,

I like the sound of this. I’m looking at Tractor Supply, but could you tell me which one it is? Maybe this one? Ideal Instruments 50cc ProShot II Syringe?

Lindy
Reply

I go into winter with two deeps and one medium on my production hives (a HBS idea, I believe…). Late fall finds the bees down in the deeps. Would it be better to remove the medium prior to treatment?

Rusty
Reply

Lindy,

I would go down to where most of the bees are. So yes, just remove and then replace it.

Peter O'Donnell
Reply

oxalic acid application

Rusty
Reply

Hi Peter,

Is this a question? Correction? Random thought?

Don’t know how to answer.

Bob
Reply

When I use the product offered by Dadant, it is recommended not to have the honey supers on or the honey will take on the taste of thyme. I notice you do this in the fall . . . after you have collected the last of your honey or do you not need to worry about flavor issues with oxalic? I’ve been looking for a better way to handle mites – this may be it! Looking forward to feedback on my question above.

Rusty
Reply

Bob,

The EPA label says not to use oxalic when honey supers are present, so I would go by that. In any case, if you use it in the late fall, you wouldn’t have supers on.

Boyd Young
Reply

Rusty this statement comes from your post “Because oxalic acid will not kill Varroa in capped brood, I like to apply oxalic acid at times when little or no brood is present but before it is crazy cold outside. For me, this is late fall.”

My question is this: If the winter bees are raised in September and you don’t treat until after that time, haven’t the mites already been feeding on the bees and already introduced the different viruses into the winter bee population? If this is true, by treating after the winter bees are raised, you are still going into winter with less than healthy bees. Guess I had thought that is why I had been treating in August/early September to lower the mite count before the winter bees were infected by the mites.

Boyd

Rusty
Reply

Hi Boyd,

My intent here was to explain how I do an oxalic treatment, not necessarily how I manage mites throughout the year. But you are absolutely correct. What I’ve been doing is knocking the mites back at the end of August with Hopguard or Thymol, and then preparing for spring with the oxalic later in the year.

Mitch
Reply

Great info, Rusty. Exactly what I’ve been looking for. Is there a danger of applying a wet treatment in northern climates during the cold months? I’m concerned about killing bees by directly applying cold syrup. Many thanks.

Rusty
Reply

Mitch,

I think there is always a danger of wet treatments chilling the bees, so I think the amount of danger would depend on where you are. Around here at winter solstice, I can usually find a warmish sunny day. I’m referring to a day in the 40s F with direct sun that warms up the hives a bit. If I’m doing more than one brood box on a hive, I keep the moisture quilt or lid on one box while I’m treating the other, just to conserve as much heat as possible . . . and I work fast.

Jerry
Reply

You might try using a diabetic syringe with the needle still in place. The needle is usually extremely thin, thinner than a hair. The thin needle constricts the flow of solution and causes back pressure preventing it from all squirting out at once. You get very exacting control with a very thin stream of liquid. I haven’t tried this with a thicker solution like a syrup, you might need a thicker needle to draw and distribute the solution; but this works in my wood shop with water, oils, alcohols, or anything else that needs a very controlled amount of application, especially in tiny spaces. And talk about distance : you can not only squirt it half way across the room, but out the front door and half way across your lawn too.

Thanks.

— Jerry.

p.s., that is a great picture of the mites; yikes, I’m glad I’m not a bee. And please don’t anyone follow up and tell me I probably have dust mites on my pillow or something like this in my eye lashes. Yaaaagghh, yikes, yuck, ick ick.

Rusty
Reply

Jerry,

I thought of using a needle, but I don’t want to accidentally inject myself with oxalic acid. With all those bees around, I don’t trust myself.

Jerry
Reply

I can understand that. If you take the tip of the needle and rub it across a fine grit sandpaper, or better yet a sharpening stone, you can take the sharpness off the needle. After that it takes quite a hard poke to actually stick yourself. You want to be careful and drag the needle tip (it is ground at an angle) away from the center of the needle to prevent the tip from being bent over and block the hole.

You can also shorten the needle to say 1/8th of an inch, but that can take some work. Sometimes in the process you pinch the needle shut and have to grind it open again. Then you have that little sliver of a needle tip to figure out what to do with. If you use a grinding wheel the needle is so small it gets really hot quick. (I’ve never tried a dremel tool.) A slow grind by hand on a stone is probably best.

David C.
Reply

“David,
I like the sound of this. I’m looking at Tractor Supply, but could you tell me which one it is? Maybe this one? Ideal Instruments 50cc ProShot II Syringe?”

Yes, the ProShot II looks like the one. It works really well, but if you have air in the syringe it does have a tendency to drip a little between doses.

LK
Reply

Hello Rusty,

I really admire your blog and it has helped me a lot. I’m a second-year beekeeper and I have a question for you, or anyone else who can help. I went into my hive today and the bees were calm, but somewhat sluggish. The weather was sunny and the temperature was almost 60 degrees F. However, the humidity was around 25% so it felt a bit colder. Anyway, is this behavior normal for this time of year, or was it the weather?

Thank You,
LK

Rusty
Reply

LK,

At 60 degrees, I would expect them to be busy. Do they have plenty of food? Sometimes bees seem sluggish if there isn’t enough to eat; that’s the first thing I would check.

LK
Reply

Rusty,

Thank you for responding. Yes, the bees have plenty of honey to eat. It just seemed odd to me, because they were busy yesterday but not today. It’s supposed to rain the next day, so maybe that is why they were acting funny.

Rusty
Reply

LK,

If they think rain is coming, they will stay home. That could be what you are seeing.

LK

Rusty,
Hopefully, that was the problem and not something else.
Thank You,
LK

Sean
Reply

Hello Rusty. I prefer the vaporizer method as it’s much kinder to the bees with no OA ingested. I use it through the mesh floor so no need to open the hive in winter and disturb the bees. I use only 2-3 g per hive which can be used more than once with no ill effect on bees or brood. Once you’ve got the vaporizer it’s quick, easy and cheap and there’s nothing to clean.

Rusty
Reply

Sean,

What vaporizer do you use?

Mark Luterra
Reply

Thanks for posting, and I’m glad I inspired you to try this. With December oxalic acid treatment, liberal fall feeding, and moisture quilts I am now 20 for 20 on winter survival – three consecutive years with no losses. I am sure that streak will end some time…

Even with oxalic I can’t get by with one mite treatment per year, but I can usually ignore the mites from December until after honey harvest in August, so I don’t have to worry about mixing mite treatment and honey production.

I’ve definitely applied more than 50 ml to strong hives, with no ill effects so far. I just do 5 ml per seam of bees, reducing accordingly for partial seams, e.g. 3 ml for a seam that is 60% filled with bees.

For preparation:
I use Randy Oliver’s medium-strength formulation, using distilled water as calcium in hard water reacts with hard water producing a cloudy precipitate. It would take a lot of calcium to actually reduce the concentration by a meaningful amount, but distilled water is cheap. The acid needs hot water to dissolve, but I try to let that mixture cool to the point where I can touch it before adding the sugar. In warm conditions, sugar and oxalic acid react to form bee-toxic hydroxymethylfurfural (HMF). If saving acid syrup for later treatment, it needs to be refrigerated.
http://www.dave-cushman.net/bee/oxalicstorage.html

I’m not sure what to think of this spring. The bees are 2-3 weeks ahead of the last two years, and a couple of hives have 12-14 frames of brood with brood in the super above and the super 1/3 filled with nectar. I’m thinking it will be a long slog of swarm prevention and a long dearth later on. I’m happy to see them booming, but I’m not sure great things will come of it…

Rusty
Reply

Mark,

Whoa! That’s some kind of a record: 20 for 20 three years running!

Thanks for the tips on oxalic. Although I use distilled water, I forgot to mention it, so I will add that in, along with the HMF.

I’ve lost one of ten so far this winter, but I have two that are not strong. The bees have been out foraging like crazy, not finding much, but losing foragers in the process. I’ve been feeding a lot, hoping I can pull them out of it.

Mark Luterra
Reply

Not 20 for 20 three years running.
2011 0/2
2012 5/5
2013 5/5
2014 6/6 plus 4/4 on nucs but three of the nucs have very small clusters.

Rusty
Reply

Mark,

That is still very impressive. Good work.

Sean
Reply

I use a Varrox vaporizer which is easy to use and gentle on bees and brood

Jean-Claude
Reply

I vaporize O.A. in late fall; it’s a quick and easy technique that involves not opening the hive, which, in this season is good. I can treat an apiary in less time than with any other methods.

With syrup, in Europe, we use 5ml per seam occupied by bees so not necessarily 50ml/hive. Oftentimes 35 ml. A syringe for sheep treatment has a dose-application device: exact amount at each squirt!

The main program in organic beekeeping in Europe is formic acid in late summer since it penetrates the cells thru the cappings and does not harm the brood – but there is a certain percentage of queen loss – followed by O.A. in late fall/early winter.

Another program that is starting to emerge, developed in Italy, is made of 2 O.A. treatments. The first is applied after the queen is caged at the end of the main flows to block egg laying (Scalvini cage). When the colony is brood free, the queen is released and the treatment is applied (syrup, spray or vapor). That way there is no queen loss as with F.A. The 2nd O.A. as usual after natural stop in egg laying.

There is no resistance from the mite to acids.

Rusty
Reply

Jean-Claude,

What kind of vaporizer do you use? I like the idea of not having to open the hive in winter.

Laura
Reply

Rusty,
I saw you ask a couple of times about vaporizers, but didn’t see a response. I bought a vaporizer this month from OxaVap. (https://oxavap.com/product/varrocleaner-oxalic-acid-vaporizer/). It’s easy to use, although I did have to use electrical tape to attach the entrance sealer to the wand, which also helps keep the dish at the end level while it’s heating.

I couldn’t wait until winter to use it because my hives were hit really hard by varroa this summer and I couldn’t use hopguard or most of the other thymol-based treatments because the instructions said daytime temps should be around 85, which in Central Texas might not happen until late October, and my hives were really suffering.

I have brood in most hives, so 3 treatments over 3 weeks were necessary, but I vaped a broodless hive yesterday and the 24-hour mite fall was 238! Holy cow! Most of my hives have had a fall of around 100 the first day after treatment and then significantly lower after the 2nd treatment. I’ll do another sugar roll count after all the treatments are finished.

Just thought I’d share my experience with the vaporizer method. The bees don’t seem disturbed by the vapor and I only have to open the hive to remove the supers.

Rusty
Reply

Laura,

I would love to try this, but there is no way I can lug a car battery up the hills to my hives. Too steep and narrow.

Nel
Reply

Thanks for this information. We have 6 top bar hives and one Langstroth (we let the bees make their own comb in the Langs, just provided starter strips – it worked beautifully). We have been keeping bees for 4 years and have never treated. We plan to start treating this year. Do you have another post where you discuss how to use Hopguard and Thymol? Are these natural products? I guess we would need to use vaporized oxalic acid on our top bars. I do hope that Sean (posted above) replies regarding the vaporizer that he uses.

Rusty
Reply

Nel,

Yes, there are a number of posts, especially on HopGuard. Just use the search box.

Brandi
Reply

This will be my first year with bees. I am starting with two hives. I have heard of a natural oxalic strip made with strips of paper soaked in the water from boiled rhubarb leaves. Do you know if this works or not?

Rusty
Reply

Brandi,

It is my understanding that the amount of oxalic acid in rhubarb leaves varies considerably, but an average number is about 0.5 percent. If you boil the leaves in water, it will be even less. The treatment level I’ve been using (35 grams oxalic acid per liter of syrup) yields a 3.5 percent solution (weight-to-volume) of oxalic acid. So my guess is that the homemade strips would not be strong enough.

Adrienne
Reply

Hello Rusty,

I’m an Ophthalmic OR nurse and we use blunt tipped 27G cannulas on syringes during cataract surgery. These are fine, metal tips that fit onto the end of any standard luer lock syringe. They allow for exact control & delivery of solutions to a given area without the risk of skin puncture. I’m not certain how a 1:1 sugar solution would flow through them, but would be happy to send you a few for experimentation.

Another thought utilizing medical supplies would be to use the soft catheter tips from any standard IV catheter set. During IV insertion the sharp needle punctures the skin & vessel but is then retracted, leaving the soft, flexible catheter behind.These can also fit onto a syringe and would give control without risk of a needle stick. They can also be trimmed to a shorter length if you wish. I have used them several times when feeding solutions via a syringe, to newborn rabbits & birds.

The one down side with either method would be that one would probably need to fill the syringes with the sugar/oxalic mixture first without the cannula/catheter tip in place. The tips are fine enough that I think it might be a slow, frustrating process to try and fill the syringes with them attached.

Rusty
Reply

Adrienne,

Sounds promising; I’d love to experiment.

Adrienne
Reply

Rusty,

I will send you off some syringes & tips to play with!!!

I think what I may try next fall, is to pre-load individual syringes with 5ml of oxalic/sugar solution. I will put IV catheter tips on them and just have 8 of them at the ready when I open my hive. Sounds a bit like overkill, but I have the resources at my disposal and with this method I won’t risk overdosing my colonies.

We shall see!

BTW, I had the pleasure of hearing Dr. Dewey Caron speak yesterday @ the Delaware state bee meeting. Dr. Caron was my professor @ the U of Maryland where I studied Agriculture and he is just as dynamic a speaker now as he was back then. His topic yesterday was on tips for successful overwintering, with a concentration on Varroa management. Like you, he advocates utilizing a variety of strategies from IPM to a rotation of soft chemical treatments.

Thanks to both of you for helping me to be a better beekeeper 🙂

Rusty
Reply

Thanks Adrienne! I sent you an e-mail.

just for the love of bees
Reply

How about breeding healthy bees that fight varroa mite naturally so we can promote healthy bees vs using poisons in our hives and our food?

Rusty
Reply

How long have you been breeding honey bees? I have some tricky genetics questions, if you’re up to it. I’m particularly interested in how to deal with commercial drone saturation in built-up areas, and what is the likelihood of slowing gene flow from these drones into breeder populations without using II.

Adrienne
Reply

Dr. Caron stated yesterday that he feels in the future the honey bees will develop resistance to Varroa, on their own, as they have in Southeast Asia. But in the meantime, and since we have no idea how many decades that mat take, he feels our best option is to help them along with as little toxins as possible.

I dislike using anything on my bees, but I will tell you, I firmly believe that a very late, emergency treatment w/ Formic acid on Nov.4th saved my colony.

I would have felt like an irresponsible steward of my bees if I had not availed myself of the resources out there. Sometimes, unfortunately, it IS better living through chemistry!

Wayne Davidson
Reply

This is a great way to apply oxalic acid. What about applying it in the spring to a new package of freshly installed bees? Since they probably came with some mites and the mites won’t be in any brood since there isn’t any, wouldn’t it be a good time to treat the bees?

Wayne

Rusty
Reply

Wayne,

Yes, it would be a good time to treat.

Gretchen
Reply

Hi Rusty,

Do you have suggestions for treatment in a top bar hive with OA? I understand the dribble method, but could this be applied to a top bar hive this fall with several full bars of honey, which I hope to leave for the bees? I see references to not using OA with honey supers in place, so how would a person use it in a top bar hive, either with dribble or vaporization?

Your blog is great, and very helpful.

Thanks!

Rusty
Reply

Gretchen,

You don’t want to leave honey supers in place if they contain honey meant for human consumption. If the honey is for bee consumption, it doesn’t matter. You can do it the same way. I take out a bar or two so I can separate the others a bit, dribble in the spaces, then push the bars back together. Or use vapor.

Melinda
Reply

Hi! Just came across your blog. I am a total newbie and live in Southern California. I am experiencing a pretty bad mite infestation which I had been treating with Apivar, with little improvement. I’d like to use the OA method, probably vaporization, but my main question is this – most uses refer to Winter, when brood does not exist. A) In my temperate climate will the queen continue to lay throughout the year and will I actually have a period of no brood? And B) can it wait until winter or should I treat now, and use subsequent treatments for emerging brood, or is this too difficult on the hive?

Thank you!

Rusty
Reply

Melinda,

I’m really surprised that Apivar didn’t work. That’s scary because it’s the heavy-hitter for when nothing else works.

You will still have a period of low brood rearing at about the winter solstice. That is probably the best you can do that far south. If you treat now, you won’t get the mites that are sealed in with the brood and you will damage much of the open brood. Now is definitely not the ideal time, but if the colony is going to succumb to mites, you may have to risk it.

Mary P.
Reply

Hi Rusty…you mentioned dragging a car battery up a hill to your hives. You can use a 12V tractor battery, about 35 amps, which weighs about 4 pounds. I just saw it done about a week ago; the mite corpses on the sticky board was impressive…and scary.

Rusty
Reply

Thank you, Mary, that is good to know. Everyone keeps telling me I need a car battery, but the path to the bees is steep and narrow. However, four pounds would work. I’ll look into it.

Laura
Reply

The battery I’ve been using is a motorcycle battery and it doesn’t weigh much. I did have to recharge it after about 9 uses, but it was easy.

Also, I did a sugar roll this week on my hives that had the worst mites. Before treating, I had 12+ mites/200 bees. Horrible! After 3 treatments, one hive had 0 mites/200 and the other two hives only had 1 mite/200. Yay!

Jane
Reply

When treating with oxalic acid, do you treat each box on the hive or just the top box?

Rusty
Reply

Jane,

Remember, you can only apply 5 ml of solution per seam of bees, up to a maximum of 50 ml (or ten seams) per colony. So it makes the most sense to apply it where the majority of the bees are. For example, you may want to apply it to the center five seams in each of two boxes, if that’s where the bees are.

Dan
Reply

What do you do with all the extra mixture if you only have a few hives? Can I just dump it down the drain or compost? 1L is a lot and I only have two hives.

Rusty
Reply

Dan,

I would just dump it over a pile of rocks or gravel where it will get absorbed into the ground. It’s a naturally occurring substance, so it shouldn’t do any harm. It’s hard to mix small quantities and still get the proportions right, but if you have a good scale you can probably cut the recipe.

Dinah
Reply

Well, I messed up cause I didn’t read all the way through the comments, so I foolishly did not think to pull the top bars apart. Duh! So I just dribbled along the tightly closed seams.

Do you think I should open up and reapply, or take my chances, especially as late in the year. It’s my first year, and I just couldn’t figure out how to treat.

If you think I should retreat, how far apart are the bars? Does the solution just dribble down onto the comb??

I did a sugar check, so I know I have mites in there. One hive has a good queen, but not very many bees. I’m pretty worried it’s doomed. the other has a good queen and lots of bees. I think it’s got a fighting chance.

Thanks so much for your site. It’s really helped me!

Rusty
Reply

Dinah,

Well, I would do a sugar roll test and see what your mite levels are now. If you still are finding mites, I would retreat. I would think not much went down between the bars. I take out one or two end bars, just so I can space out the others while I treat. A quarter-inch or so, should do it, and then slide them back together when you are done. Yes, it just dribbles down and then the bees clean it up which moves it all around the inside of the hive.

Dinah
Reply

I’ll do it!

Thanks!

Sue
Reply

Hi Rusty,

I live in New Zealand so it is late spring here. I was late treating my Top Bar Hive for Varroa with Api Life Var and now am into week four of a 4 week cycle. I still have some white mites in the debris on the bottom board which I understand are males.

I am most interested to read of being able to use oxalic acid in a TBH using the dribble method!!!

My question: Shall I continue with Api Life Var a bit longer (and for how much longer) as bees are actively gathering pollen OR can I try the oxalic acid now given our season and the fact there will be capped brood?

Your site is a most interesting one. Thank you.

Rusty
Reply

Sue,

Since you are in the last week of the four-week cycle, I think it would be best to finish up the cycle and treat with oxalic acid much later, as you go into winter. I’m guessing here, but I think it might be hard on the bees to treat them with ApiLife Var and then oxalic right after.

I understand that you are eager to get the treatments done since the pollen is coming in, but you are so close to being done anyway, it seems risky to add another chemical.

Sue
Reply

Thank you Rusty for your advice.

As I write my bees are settling after swarming just over an hour ago. What a spectacular site! Conveniently they have chosen a low branch on a nearby tree. I have called my local bee club and someone whose approach to bee keeping I respect, is coming this afternoon to gather them. I am not sure yet how many bees remain in my TBH.

Andrew
Reply

Hi Sue,
Here in Europe we treat the bees with the oxalic acid dribble method with a maximum of 50 ml oxalic solution (30-35 gr oxalic acid/liter 1:1 sugar syrup) repeat once with a bad infestation, more often is not advised.
This method is used near the winter solstice with temperatures close to or below 0 degrees Celsius. That is the time there is the least chance of brood and the bees will be packet together against the cold.

An other method is by making a broodless artificial swarm and treating the bees with a pressurized plant mister.

Dave Stokes
Reply

Hi Randy, a good article and a good web site, but I do have a few issues with it and some of the comments.

Andrew was right when he said, “If the bees do not occupy that seam then don’t apply the acid.”

I would go further and say, if you only have half the number of bees in a seam you only give half (2.5 ml) a dose. The dose should be aimed at getting the right dose per bee. It is my understanding that syrup is used so that the bees will share it around.

Here in the U.K., Apivar hasn’t worked for about 10 years because it was abused. Oxalic acid isn’t adequate by itself here, I reckon on using several treatments: Formic acid, thymol or other hard chemical in the summer, oxalic acid whenever I have broodless bees (swarms whether artificial or natural), if I use Demarree or Snelgrove to make an increase, both the mother and daughter colonies go through a broodless phase, and of course, at or about the winter solstice. However, ideally a queen should only get one dose a year.

I addition, I sacrifice the first drone brood of the year (where all the varroa is) and use an icing sugar shaker at each colony inspection (it might not do much, but every little helps).

For the last few years here, the problem has not been the varroa as such but the viral diseases that they bring; ee have to adopt a zero tolerance approach.

I hope these comments are useful.
Thanks
Dave.

Rusty
Reply

Dave,

1. Rusty, not Randy.

2. You emphasize “If the bees do not occupy that seam then don’t apply the acid.” And I wrote, “Dribble 5 ml of the solution along a seam that contains bees. That is different somehow?

3. You write, “I would go further and say, if you only have half the number of bees in a seam you only give half (2.5 ml) a dose.” And I wrote, “Alternately, you can give less than 5 ml per seam and do more than 10 seams, but you cannot go over 5 ml in any one seam or 50 ml total per colony.” I really do think you are splitting hairs.

4. You write, “For the last few years here, the problem has not been the varroa as such but the viral diseases that they bring.” It’s been a good deal longer than the last few years. Varroa mites never killed the bees, but viruses do.

Alex
Reply

If you winter your bees in 2 deep brood boxes with free choice to lay brood where ever they choose do you do 50 milliliter each box or total on the hive? Also would you treat with OA or Apilife Var in the mid to late fall? This is my first time finding mites in any of my hives (I know I had good blind luck for years) so I’m clueless on how to treat in late October/early November. Thanks again for all your help!!!

Rusty
Reply

Alex,

Fifty milliliters of OA is the maximum dose per colony, not per brood box. I like to knock down the mites with ApiLife Var in late summer or early fall and then treat with OA close to the winter solstice when there is very little brood.

Alex
Reply

Thank you I couldn’t find apilife var anywhere for sale, every place I tried was out of stock. I was able to get mite away quick strips but I’m afraid treating this late in the year might backfire. My 24 hour mite count on my two hives is around 30 and 7. With those numbers would you use the strips or just wait until December and use OA and save the strips for a spring treatment of needed? As always thanks for your opinion!

Rusty
Reply

Alex,

Those are high mite counts. I would treat asap.

Sean
Reply

You can vaporise oa any time of year, I’ve seen no harm to bees, brood or the queen. It doesn’t stop the queen laying and if you treat with brood in the hive, treat three times five days apart to complete a hatching cycle. I use no other treatments and never have. I always treat from below the mesh floor to make life easy, very gentle on the bees!

Rusty
Reply

Sean,

I guess I’m going to have to break down and get a vaporizer. Does your use a battery?

Sean
Reply

Yes I use a small 12v car battery, I use 2.5 grams per hive, 2.5 minutes on heat 2.5 minutes battery off and hive closed for a further 5 minutes. Once you’ve bought the varrox there is no more cost as the OA is so cheap, 1kg will last years.

Joney
Reply

Hi Rusty,
Your blogs and the info you give are all so very helpful. For all the info; past, present and future, thank you!
My one question for now is: where may I get a good source of oxalic acid? Is it as simple as buying ‘Wood Bleach’ at the hardware store or is it best to get it from a pharmacy?
Thank you again,
Joney

Joney
Reply

Whoops!
Dear Rusty,
I just went way back in this blog to the top and noticed right off the bat you answered my question! Thank you I will try the Savogran 10501 Wood Bleach.
Cheers,
Joney

Rusty
Reply

Joney,

Excellent. I was just now looking it up for you, so I’m glad you found it.

George
Reply

Hi Rusty: Greetings from CT.

I’ve been using an OA vaporizer for a couple of years and have had mixed results. If using it with capped brood, I think what is crucial is that you rigorously treat a hive every 5-6 days to catch all the hatched mites and prevent the adult females from burrowing into the brood. I would apply the vapor 4x. If mis-timed it’s all for naught.

As for the equipment some thoughts:
– invest in a garden tractor battery (they run about $30) and leave it at your hive site. It should power a couple dozen 2 minutes vaporizations for a given charge. Then you can bring it back to your house to recharge.
– the vaporizer gets very hot and I thought I could quickly cool it down to quickly reload it with OA for the next treatment by quenching it in water, then drying it with a towel. (If you put OA directly onto a hot vaporizer you risk getting OA vapors outside the hive.) This turned out to be a bad idea because I eventually broke the vaporizer’s head by repeatedly drying it. These devices are kinda delicate and don’t take much abuse.
– plan for about 5-7 minutes of treatment per hive, a minute to load the device, 2-3 minutes to vape, then a couple of minutes to cool down and lug the equipment to the next hive. I have 10 hives and it runs me a bit over an hour. Do that for 4x on-schedule treatments, and it becomes a time sink with equipment to lug around.

I’m beginning to think that vaping is best used in the winter when there is no brood (thus needing only one application) and it’s too cold to open or OA drench the hives.

You have a great site, thanks so much,

George

Tom
Reply

Rusty,

Has anybody tried a LP vaporizer that is used for mosquito fogging? It just uses a small camp stove type LP tank and is very light and portable.

I’m getting 2 packaged swarms with queens soon. It sounds like it might be a good idea to spray them down with the OA and sugar solution from the get-go. Yet, I haven’t really read this as a reccommendation. Would it be harmful. It would seem to make sense.

Thank you for the site….I’m learning a lot. I’ll be sure to donate.

Rusty
Reply

Tom,

Yes, applying oxalic acid to packaged bees is often recommended. It is an ideal time because there is no sealed brood (or any brood at all).

Matt
Reply

Hey Rusty, I have a quick question… After reading this article Im wondering if you have stopped using essential oils in your hives? After doing a search it appeared that your advocacy of using EOs for controlling Varroa is several years old. Do you still use them or have you switched to other methods? Do you have an article about it? Thanks!

Rusty
Reply

Matt,

As a mite treatment, oxalic acid can be grouped together with the organic acids and essential oils. Formic acid, oxalic acid, thymol, and hop beta acids all fit in this category. Any mite treatment should be used in rotation with others to prevent (or reduce) resistance by the mites. So no, I haven’t stopped using the others, I just added one to the rotation.

Bill
Reply

Rusty, Great post and follow-ups! However, I’m not seeing any evidence that the acid is actually ridding the hive of mite with the drizzle method. Did you by chance install some kind of sticky board under the clusters to check effectiveness? If so, you have any photos to support?

As always, I enjoy reading your blog.

Bill

Rusty
Reply

Bill,

The most awesome mite drop I’ve ever seen, and it was absolutely incredible, was achieved with an oxalic acid dribble down in Oregon. I’ve asked the beekeeper if he still has the photos. If so, I will post them. Otherwise I will have to wait until the next time I treat to take photos. But you can be assured that the results are unreal. It was right after I saw his results that I switched to an oxalic dribble.

Linda
Reply

Hi Rusty

I am trying to decide between the oxalic dribble and the vaporizer. After all that I have read I can’t figure out which is the safest for me and the bees. Also can’t figure out exactly when to do the treatments. And how many times. Once site says 3 times 5 days apart and another says only one treatment per year. Etc. I am now totally confused. Any thoughts on this?

Rusty
Reply

Linda,

Yes. My thought is to go to reliable sources for your information. A good place to start is the official EPA label for oxalic acid. Read the whole thing because there is lots of good information there including how to mix it. It says specifically “Use only in late fall or early spring when little or no brood is present.” The label is silent on using it multiple weeks in a row, but it does say, “Consult state guidelines and local extension experts for monitoring protocols and thresholds for treatment.”

When I go to Washington State University Extension, it sends me to Randy Oliver’s site for tips on using oxalic acid. This is where I learned how to do it, and I think it is the best current information. Randy doesn’t follow the label exactly, but close. He talks about using oxalic in three consecutive weeks in summer but does not recommend it in winter. He says summer bees tolerate it better because of fast turnover. I recommend reading all of Randy’s article.

My post here is largely a distillation of Randy’s post, or at least my interpretation of it. It may make more sense after you’ve read these other documents. Personally, I lean toward not using it three weeks in a row, but the EPA doesn’t prohibit it.

Remember too, that mite treatments must be rotated to avoid developing resistance. Both the EPA label and Randy are adamant about this. So if you use oxalic this time, use thymol, formic, or hop beta acids next time.

Robin @HoneyGirlGrows
Reply

Hi Rusty:

In CA we have NO real “winter” nor period where there isn’t capped brood. I have been mentored by Randy a bit and he is caging the queen (I am guessing for 12 days) to create a false winter so the brood birth out. He treats, then releases her. I have heard the vapor is much more gentle on the bees and am wondering if there’s any scientific testing/evidence of this? They’re so expensive. Perhaps I can talk my bee club into getting one.

PS
I want to give you HUGE thanks for your site. I’ve been referring it to beeks like crazy on my Instagram @HoneyGirlGrows. I’ve read the hell out of this post and all of the comments and want to thank you for giving me confidence with this!

Rusty
Reply

Robin,

I too have read that the vapor may be more gentle, but I haven’t seen any statistics on how much more. Of course, if people want to sell you something, they will say it’s “much” more. I’ve used the dribble with no apparent bee mortality, and I end up with fine healthy colonies the following spring. I don’t believe all the gadgetry is necessary, except to those who love that kind of thing. I like simple.

Kristen
Reply

Hi Rusty,

Love your website. I am on week 3 of treatment with ApiLife Var. I did a mite count today on the sticky boards and there is still a high mite count. I was planning to do a follow up treatment in October with Hop Guard, now considering the Oxalic Acid dribble. Would that be overkill following the ApiLife Var?

I am in eastern Washington state where winters are quite cold. So, I would do the Oxalic in late October during a time of low brood.

Thanks, Kristen

Rusty
Reply

Kristen,

For whatever reason, I sometimes don’t get excellent results from ApiLife Var. Usually I do, but sometimes not. I think it would be reasonable to do a follow-up treatment with oxalic acid, especially at a low-brood time of year.

Robin @HoneyGirlGrows
Reply

Hi Rusty:

I’ve been informed by Randy he is caging the queen (12 days) to create a false winter so the brood birth out. He said to be cautious not to stick her into the honey band or you can drown her.

*Randy highly advised AGAINST using a vaporizer.

He said Oxacalic is really safe, until you make it small particles that are airborne. He referenced someone’s kid passing out in a bee yard.

**Randy uses a pump sprayer — easier than the syringe.

***Oxalic is available on amazon

On his site Randy has updates to Oxalic Dribble that make things a bit more clear. He finds treating in summer with it is more effective than winter and states why.

It might be a good idea to delete some of these comments that add to the banter of non-accurate info, or better yet, update and repost this blog post all together — the comments are long and include a lot of misinformation. That includes my previous comment with my impression (not based on science, but based on others’ words), that a vaporizer was easier on the bees.

Thanks,
Robin

Rusty
Reply

Robin,

Randy Oliver is my go-to guy and I have (and continue to) learn much from him. I frequently mention him and link to his work. From day one he has promoted oxalic acid delivery methods other than vaporization. I first learned the dribble method from him, and that is the one I still use.

However, this is not Randy’s website. Furthermore, not every one agrees with him. That is fine. Beekeepers never agree and disagreement in no way diminishes Randy’s work. The point of comment and discussion is a back-and-forth sharing of both facts and opinions, and I will not delete comments because you don’t agree with them.

I do delete some comments, as I have outlined elsewhere, that are rude, inconsiderate, ridiculously off-point, or that contain foul or profane language. I also speculate that some comments go directly into spam and I never see them, but that is a separate problem.

Randy’s use of a pump sprayer rather than a syringe is fine, and especially appropriate for people running hundreds or thousands of hives as he does. For people running just a few hives, the time and ease differential will be marginal.

Sequestering the queen while the brood hatches is also an excellent idea, although it probably is not for everyone.

Oxalic acid is available everywhere, including Amazon and your local paint and hardware store. I bought mine at Home Depot.

I don’t believe it is misinformation that vaporization is easier on the bees. Some researchers have shown otherwise, some beekeepers believe otherwise. Like everything else in beekeeping, results will vary between individuals, between hives, between regions, between subspecies, between seasons. There is no one right answer.

Personally, I don’t use a vaporizer and don’t intend to. I have repeated my opinion several times that a dribble is perfectly fine for small operations and I think a vaporizer is a waste of money. My thoughts are very clear in the recent post “How to torch your hive with an oxalic acid vaporizer.” But if other people want to use that method, that is their decision, not mine. The point of this blog is to illustrate alternative methods and alternative ideas. It is not to dictate protocol.

I think the most important point on Randy’s website is that varroa treatments must be rotated. As sometimes happens, Randy provided information for my post before it was published and I got the thumb’s up from him. There is nothing here to belittle Randy’s work. Even when we disagree on specifics, we are on the same page when it comes to principles.

Melissa
Reply

HI Rusty, I’m in the Willamette Valley, Oregon. I have top bar hives. I’m thinking in November it is probably wet and cold. I’m wondering if early October would work for a dribble approach? I read no temps above 70?

Thnx

Rusty
Reply

Melissa,

An oxalic acid dribble is best done when there is a minimum amount of brood, which usually means somewhere around the winter solstice. I did my top-bar hive last year on the day after Christmas. Yes, it is wet and cold. But the job takes only about three minutes. And since there is little or no brood, the brood does not get chilled. It’s perfect timing. The adult bees withstand that much cold and wet with no problem. If you pay attention, you can usually find a 50-degree afternoon at that time of year, especially in the Willamette Valley.

Josh
Reply

Hi Rusty,

Thanks for your time and your information. I read in some european sources that the dribble oxalic method must be applied 4 times waiting 4 days. I mean, imagine today is 1 of November, then we would applied today, another time 4 of Nov, another time 8 of Nov, and last one on 12 of Nov. I think this is for complete the varroa cycle, but with broodless have no sense. May only for spring application have sense.

Do you think repeating the treatment is dangerous?

What do you recommend: Apply only one time in one day or do 4 times?

Thanks

Rusty
Reply

Josh,

Oxalic acid doesn’t kill varroa that are living with brood and protected by wax cappings. So, you can either use it once when there is no brood, or repeated times when there is brood. Successive applications allow you to kill the varroa as the brood emerges.

However, reports indicate that repeated dribble applications are hard on the bees, and that if you must do repeated applications, vaporizing is the better option.

Personally, I use just one application during a low- or no-brood period in winter. Then I use a different product in August before winter bees emerge, usually a thymol or formic acid preparation.

I have heard of other people who use multiple dribble applications with good results, but I have no personal experience with that.

David
Reply

How long do dead mites continue to fall after an OA dribble?

I got a good drop from my colonies the first couple days but mites are still dropping (7-20) a week later. I didn’t check every brood frame before dribbling (it’s a bit too cold for that where I am), but I didn’t see any in the middle of the brood box, so there’s probably not much. Apiguard had mites under control in Sept (1-2%), but the bees must have brought them in from somewhere else since then. I was going to vaporize in late Dec, but figured I’d dribble now as an emergency measure. Should mites still be dropping from the dribble after a week? Thanks.

Rusty
Reply

David,

I don’t know. It’s very high the first few days, then it tapers off. But I’ve never monitored the drop for more than a few days afterward. I suspect that it is very possible to see that much drop a week later. Some of the dead mites may have gotten lodged in the comb or brood nest, or even in the cluster, and fell to the board later. Also, some may not have died immediately, but became weakened and malingered for a time before they died.

I’m just speculating here, but it seems possible to me. From what I’ve read, scientists don’t understand the mechanism by which OA kills mites, which makes it hard to figure out why you are seeing this prolonged drop.

Erik Brown
Reply

Rusty,

Happy Thanksgiving 2016! I am continually impressed how you keep answering questions on your posts months and years afterwards your original thoughts.

With that in mind, I am hoping to try my first oxalic acid dribble in a few days. I bought some OA from Amazon, and it is Ethanedioic Acid Dihydrate and 99.6% pure. On Randy’s SB site he talks about wood bleach as Oxalic Acid Dihydrate with 71% OA. So now I’m worried that following your recipe will result in a higher concentrate of OA than I need.

Doing the math would say that instead of 35 grams of a 71% OA powder, I should use 25g of a 99% OA powder. Does that make sense, or am I overthinking this?

Appreciate any insight,

Erik

Rusty
Reply

Erik,

Randy Oliver talks about this at the beginning of his OA chart. He writes, “Important Note: the following proportions refer to common oxalic acid dihydrate (wood bleach). If you manage to get your hands on pure laboratory oxalic acid, you must reduce the amount of acid to only 7/10ths of that of the dihydrate!!!!”

Erik Brown
Reply

How right you are, I totally missed that. At least my calculations worked. 7/10 or 35 is 24.5. Have a good day / weekend.

Jessica
Reply

Hi Rusty, I am about to be a new beekeeper and have a new hive. My bees arrive next week. Would you treat the package bees with oxalic? I’ve read where people have sprayed new bees with the sugar/oxalic solution in an attempt to cut down on any mites that have arrived with the package even before they put them in the hive. Since I have a new Langstroth hive and the bees are more likely to abscond already, is it advisable to treat a brand new package? Or will that just increase their chance of absconding? Or maybe it is not even that effective to spray a new package?

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