[Bonus] Short - Varroa Treatment Options: Oxalic Acid (OAV and Dribble)

[Bonus] Short - Varroa Treatment Options: Oxalic Acid (OAV and Dribble)

[music]

Jeff Ott: Welcome to Beekeeping Today Podcast Shorts, your quick dive into the latest buzz in beekeeping.

Becky Masterman: In 20 minutes or less, we'll bring you one important story, keeping you informed and up to date.

Jeff: No fluff, no fillers, just the news you need.

Becky: Brought to you by BetterBee, your partners in better beekeeping.

[music]

Jeff: Hey, everybody. Welcome to this Beekeeping Today Podcast Short on Varroa treatments. This is a multi-part series covering the different treatment options available to combat this honeybee pest. Each short in the series will cover one specific treatment option. For the series, we've invited Dr. David Peck from BetterBee to join us. In this short, we'll be discussing OAV or oxalic acid vaporization and OA dribble. Hey Becky. Hey David.

Dr. David Peck: Hey, Jeff.

Becky: Hi, Jeff. Hi, David. This is exciting because I represent oxalic acid dribble, and I'm pretty sure Jeff, you represent oxalic acid vaporization. Is that correct?

Jeff: I have the most experience with the OAV, yes.

David: I've probably done about an equal amount of both.

Becky: There you go. You're the expert on the panel, so I'm looking forward to learning more.

Jeff: When it comes down to a split decision, David, you have the overriding vote.

David: That sounds good.

Becky: He's the vice president.

[laughter]

Jeff: All right. Let's talk about this. When we talk about OAV or oxalic acid, and we talked about oxalic acid in the strip in a prior episode, this is specifically the granular oxalic acid you can buy from a bee supply store.

David: It's a powdered oxalic acid dihydrate crystal, which is just the way that you get oxalic acid. It can be applied to your colony in a couple of different ways. There are two different products that are registered that you can legally use inside of a beehive, and they are both oxalic acid powders, although one of them also has another formulation of the same material. Oxalic acid at its heart, is just a simple organic acid molecule. If you think about the difference between formic acid and oxalic acid, these two things that we use to treat our bees, in many ways, oxalic acid is just two formic acids glued together at the butt. They're two-

Becky: Chemistry lesson.

David: -very, very simple organic acids. These molecules are effective at killing Varroa mites and don't do any appreciable harm to honeybees, and so they are an excellent, excellent tool for mite control, regardless of which of the different methods of application you use.

Jeff: What should beekeepers be looking for?

David: The two products you can buy are Api-Bioxal, and then there's a newer registered product called EZ-OX, E-Z-O-X. Both of those products can be applied as a dribble or can be applied as a vapor. The Api-Bioxal was registered to be applied at 1 gram vaporized per brood box. Then EZ-OX came out, and they were registered to be applied at 2 grams vaporized per brood box. Now Api-Bioxal has updated their label, and they can be legally applied at 4 grams vaporized per brood box as soon as you get your hands on the stuff with the updated label.

You don't get to use the old stuff once the label gets changed, but new products that you buy will be rolling out with the 4 gram per brood box label on it. This is the advantage of having multiple products that are very similar to each other. They're both trying to get that competitive advantage by working with the EPA to get those label dosages increased so that they're more effective at controlling mites, and they satisfy the EPA's safety concerns. That's why these two products have changed and evolved more than some other miticide products have over the last few years.

Becky: I just want to clarify for myself. We're talking about a change in the OAV amount.

David: That's correct. There's no change in the dribble dosage at this point, although that's something that I know is being looked at by the folks who make these products.

Jeff: Let's split these out right now, and so that we don't keep crossing the terms. Let's talk about OAV first.

David: Sure. Because it's your favorite. [laughs]

Jeff: I stepped up first.

Becky: We're going to end with the high then on that dribble.

[laughter]

David: OAV is vaporized or sublimated oxalic acid. There's all sorts of very good chemistry reasons to get hot and bothered about which term you use, but it doesn't really matter. The point of it is we're going to use a heated plate, some heat element, to heat up these crystals and then to cause them to form a gas inside of the beehive, that gas is going to expand to fill the whole volume of the hive. Then very, very quickly, the oxalic acid will recrystallize on all of the different stuff inside.

You're going to get these tiny little microcrystals that form on the bees, on the combs, on the mites, on the wood, on anything that is touched by that vaporized oxalic acid. Those tiny little crystals being applied in that way and spread throughout the hive are what the Varroa mites will encounter that will ultimately lead to their death.

Becky: David, how about those little crystals in our lungs, in our eyes, on our skin?

David: We don't want it in any of those locations. Very importantly, oxalic acid vaporization is easily the least safe miticide application that you can do for yourself when you're treating your bees. That is because the risk of inhaling these oxalic acid fumes that come out during vaporization, getting it into your eyes can cause permanent blindness, into your lungs can cause permanent lung scarring. If you get a full dose of this stuff, you could absolutely conceivably die from it. That is why the products demand that beekeepers wear all of the appropriate safety gear.

You most importantly want to have eye protection and lung protection. That is not just putting on an old COVID mask you had lying around and trying to stand upwind of the stuff. It is a full acid gas respirator that is fitted onto your face. You got to trim the edges of your beard to make sure that you get a good seal around your face if you we're going to be applying the stuff, because you do not want to tangle with this cloud of oxalic vapor. That being said, doesn't do any harm to the bees. [laughter] Once again, another example of bees being better than humans.

[laughter]

Jeff: We jumped here. Before you apply the vaporization, what about the honey supers? Can they be on, off?

David: Again, that's an example of the original product, the original registration, you could not use it when your supers were in place. That was changed by the manufacturers of Api-Bioxal working with EPA and getting that updated. Both of these products can now be used with honey supers in place. They encourage you not to use it right smack in the middle of a honey flow. I have met people who claim that they can taste a tiny little oxalic acid residue in honey that was being on during those treatments. I've never tasted it myself.

It's not regulated in the US. Basically, the federal regulators have looked at this and they've said the tiny, tiny trace amounts of oxalic that might get into that honey are not of any relevant concern for human health, especially because bees forage on flowers that also sometimes contain oxalic acid in their nectar. The amount that you'd get in the honey, even if there was a minor contamination, is pretty negligible.

Jeff: I can't remember the product names, but one is the powder we're familiar with, but there's also a compressed tablet form.

Becky: That's right. The Api-Bioxal is only available as a powder. EZ-OX, you can get as a powder, but you can also get it compressed into these little tablets. Those 1-gram tablets are excellent if you are doing vaporization by grams, because you can put those little tablets in your vaporizer, and you don't have to sit out with a scale in the apiary trying to make sure you get exactly the right number of grams per box.

Jeff: Most of the powders include a little 1-gram scoop, theoretically is 1 gram.

David: Right, although a gram is a weight and not a volume. You just have to hope that with your scoop, it hasn't been too compressed or too fluffed up, because you might get a slightly different amount.

Jeff: The vaporization process, and this will just end on this is there's trays, the heat plate trays that slide in the front door, and there's also the vaporization, for lack of a better term, guns that heat it up and inject it into either the front of the hive or a hole that's drilled into the back of the hive.

David: Yes. Often, for the gun style, it will have a little tube that the vapor comes out of. If you drill a hole of about that diameter, you can stick it in, vaporize the hive. A lot of folks will drill the hole the right size so that they can just take an old golf tee and stick it into the hole and then plug it up. For folks who don't want to do that, don't want to modify their hives, you can also just go right in the front with those gun-style vaporizers. You just have to plug up the entrance with rags, cloth, something like that, so that you're keeping the bees inside and really getting all of those vapors to recrystallize inside and not drift out and recrystallize outside in the air of the apiary.

Jeff: That's a quarter-inch hole, just if anyone's keeping track. If you use the vaporization gun, that tube does block, and it creates quite a mess, and dangerous mess at that if it should backfire or come up through the plunger tube. You have to take care of your equipment.

David: Exactly.

Jeff: Let's talk about dribble, because that's a very easy and cost-effective way of applying the [crosstalk]

David: The vaporization is very popular. Deep in my bones, I feel like a lot of beekeepers like it because it's a power tool version of treating with oxalic acid. There's a lot of testosterone that says, oh yes, I'm going to get that cool stuff. I'm going to get my-

Becky: That explains a lot.

David: -Dewalt battery and plug it in.

Jeff: Home improvement show.

David: There's just another really just as good way to apply oxalic acid to a hive, and that is dissolving the oxalic acid into a sugar syrup and dribbling the oxalic and sugar syrup mixture onto the heads of your bees, just squirting it in-between the frames of the bees. I think that there's a bias towards thinking that the vaporization must work better. There really isn't good scientific evidence suggesting that that's the case.

For the dribble method, which is a great method, what you do is you mix it up at the appropriate dosage. You measure out 50 milliliters or 50 CCs, depending upon your syringe, of the stuff. Then you squirt it about 5 milliliters at a time in-between the frames of your colony. You start in the bottom box, and then you work up to the top box. Whenever you've dosed them with 50 milliliters, you're done. That's the full dose of the hive.

You're, in the same way as with a vaporizer, creating all those tiny microcrystals and spreading the OA throughout the hive, you are creating this sticky, wet solution of oxalic acid that the bees then track and dribble, and distribute throughout the hive. Once again, the mites are getting exposed to it as they run into those oxalic acid residues throughout the combs.

Jeff: You were saying 50 milliliters per hive, or is that per box?

David: Per hive.

Jeff: Per hive.

Becky: At the most.

David: Correct. That's right.

Becky: 5 mils per seam of bees, and then at the most, 50 mils.

David: If you don't have enough seams of bees to get up to 50, then you just stop whenever you've treated all the seams.

Becky: You just have to learn how to count by five. Also, it's a one-to-one syrup, correct?

David: Correct, yes.

Becky: That I've always heard.

David: Thin syrup or one-to-one syrup.

Becky: Thin syrup.

David: One interesting thing that I'll just mention is that I'm actually currently doing an experiment on a new product that is already available in Europe but is not available in the US yet, which is another-- it's an oxalic acid dribble, but instead of using sugar to thicken up that liquid, it uses vegetable glycerin. That product is not currently on the market, but when it comes out, which we expect it to do pretty soon, it'll be called Api-Bioxal RTU, or ready to use. That means that you don't even have to sit there and measure out 12.6 grams and dump that in and mix it up and make sure it dissolves properly. Any of the other headaches that go along with mixing up your dribble.

The goal is to make it an even easier way for somebody to grab a bottle off the shelf and treat all of their hives and then not run the risk of breathing in oxalic vapor and also not have to spend $400 or $500 on one of those oxalic vaporizers, because they sure can be expensive. There's a big sticker shock to getting started with OA. The advantage of the dribble is as long as you can afford sugar and water and a packet of this powder, it's a much cheaper way to treat your bees.

Becky: David, you said 12.6 grams. That's to how much solution of syrup?

David: Oh, you know what? I can never remember it. I always look at the label to get the dosages.

Becky: I always do it per liter.

David: The 35-gram package-

Becky: 35 gram, yes.

David: -is what you mix into 1 liter of sugar syrup. If you want to mix up that much of it, then that works great. If you've only got one hive though, it feels pretty silly to dump a whole 35-gram packet in and then only treat the one hive with-

Becky: That makes sense.

David: -50 milliliters.

Jeff: Do we know how either of these products or how oxalic acid kills the mite?

David: No. [laughter] No, we don't. We've got some--

Jeff: That's a short answer. We can move on?

David: We've got some theories. Actually, Dr. Frank Rinkevich at the Baton Rouge Bee Lab, and Dr. Lewis Bartlett at the University of Georgia, and I were all sitting around discussing this at one point. We sketched out on a napkin an experiment that we wanted to do. Lewis currently has a student who's pursuing one of the inquiries that we came up with there. The short answer is no, we don't really know how this kills mites. It's in some way that oxalic acid making contact with the mites. We think it's probably through the thin and wet footpads that the mites use to stick to the bees and to crawl around. We think that they're somehow absorbing it and then it's having this toxic effect on them. We genuinely do not know exactly how it kills them, but it sure does.

Jeff: We've talked in the past in our introductory show about the ebb and flow of Varroa in the colony throughout the year. When's the most effective time to use oxalic acid in either form in a colony?

David: The absolute best time to use oxalic acid is when you have no brood in a colony. That doesn't really matter what time of year. If your colony is broodless because you just caught a swarm or they swarmed and then failed to re-queen and you've bought a new queen, so now you don't have any brood in the hive, if you've got no cap or even open brood in the hive, that's going to be your best time because all of the mites are exposed, all of the mites are potentially going to be killed by the treatment.

The time of year that most of us most reliably have little to no brood is in the winter. A lot of folks have traditionally used oxalic acid, vaporized or dribbled, as a cleanup treatment for their fall mite treatments at some point during the winter, late fall or early winter, so that by the time their bees are starting to grow again the following spring, they're going to have few to no Varroa mites in them. That'll hopefully give the bees a good start going into the next season.

That being said, you can, especially with the new changes and the rules that have allowed you to use these things with supers in place, you can treat with oxalic acid anytime of year. The issue is it doesn't penetrate the brood gaps, and so a lot of the Varroa mites at any given time when the bees are actively raising brood are not going to be exposed to the treatment. It doesn't last long enough that the mites that are currently in the cells are going to get exposed when they crawl out of the cells. That means that ideally a beekeeper is going to be using this in a little- to no-brood scenario.

If you are using it while you have brood in place, when you treat, you're going to kill some mites, and every dead mite is a mite I want dead. I'm not going to object to that. Ideally what I would be doing is probably reapplying it. There's a lot of research that has gone into the appropriate interval in which to reapply. Do I do it once every three days for five cycles, or do I do it once every five days for three weeks? Whatever the different math might be.

The answer is all of the research that has been done is inconclusive. We do not know definitively what the end-all-be-all best schedule is for these repeated applications, but every time you reapply, you are going to kill some Varroa mites. If your mite levels are too high and you do one or two, or three, or four applications on whatever schedule you choose and you get your mite levels back to a safe level, then that's permitted and acceptable. Ideally, we would have a perfect schedule to give to everybody, and we just don't have that yet.

Becky: I like the dribble as a tool because of the temperature range that you can use it at. I think that's really important. It gives you a little bit of flexibility, especially if you really just want to use organic miticides in your colonies.

David: The ability to go out when a colony is in cluster in the winter and to treat them and not do any harm to them is really excellent. The only temperature limit that you might have for the dribble is if the colony is an extremely tight cluster on a very cold day, then you're not going to dribble on quite as many bees. It'll get on the outside bees of the cluster, but not so much on the inside. Generally you're looking for the warmest day in late November or the warmest day in mid-December, just so that bees are slightly looser, a little bit wider, and you're going to get more surface area contacted with the dribble.

Becky: We're looking at, you can do it successfully in the low to mid 30s. The 40s or 50s feel a little bit better. If you can hit those 40s in a December day and in the winter, it's a nice way to get in there and be effective and also take care of your bees, and it won't hurt them. It's really weird, though, putting a liquid on your bees in cold weather.

David: It feels crazy. It feels like you'll definitely kill them, but you definitely won't.

Becky: Do not. If they're going to die, it's because you didn't get there soon enough.

David: The one most important lesson for mite control across the board, no matter what you're using, is early and often, getting your mites under control, keeping them under control, not having high levels. The ability to use these products anytime, but particularly in that late fall, early winter, mid-winter period, gives you this huge opportunity to cause the mite levels in spring to be as low as they can possibly be. There's nothing better for your bees when they're in that spring growth and regrowth, and winter recovery and expansion mode than to have very, very few parasitic mites.

Becky: One more reason why we encourage it is once we hive a package of bees, it's a great time to get in there and get your first mite treatment in a few days after that or seven days after that, just so that you can get a reliable treatment in before any brood is sealed. The spring temperatures are always going to work with that.

David: Neither of these treatments is hard on a colony. There are plenty of treatments that I wouldn't want to put into a swarm or a package that I had just installed, but I wouldn't worry about either of these causing bee death or absconding, or anything like that.

Jeff: One last question to wrap this up. Is there any problem with rebuilding resistance using oxalic acid?

David: I'll never say never. I won't say that we will never see a mite that is resistant to these molecules. It's particularly hard to comment on it because we don't know exactly the mechanism through which they kill the mites. If you don't know what the mechanism is, there's no way to figure out, could the mite mutate an oxalate receptor or a pH pump? We don't even know how they're killing them. We don't really know what the resistance would look like.

That being said, there has been no report of any kind of resistance to these organic acids by Varroa mites. At this point, we don't have any evidence or even reason to suspect that they are likely to develop it. I'll never say never, but I think the odds are very poor that you're going to see mites resistant to these oxalic acid or other organic acid treatments.

Jeff: Becky, David, this is another great treatment option for beekeepers to use in this battle against Varroa. I think it's a good one to have in the tool belt for keeping after the Varroa, but as part of an overall plan, it's just one of many different options.

David: One of a number of really handy tools to have in the back pocket. Whether you want to vaporize or dribble, the ability to use oxalic acid is a huge opportunity for beekeepers to get their mites under control.

Becky: David, thanks so much for your expertise.

David: It's been a pleasure.

[music]

[00:21:23] [END OF AUDIO]