[Bonus] Short - Varroa Treatment Options: Varroxsan

[Bonus] Short - Varroa Treatment Options: Varroxsan

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Jeff: Welcome to Beekeeping Today Podcast shorts. Your quick dive into the latest buzz in beekeeping.

Becky: 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.

Jeff: Hey, everybody. Welcome to Beekeeping Today Podcast shorts on our continuing series on Varroa treatments. Hi, Becky. Hi, David.

Dr. David Peck: Hi.

Becky: Hi, Jeff. This is exciting. I love talking about ways to kill mites.

Jeff: Who's going to kick us off?

David: We're going to talk about VarroxSan. It is an extended-release oxalic acid strip. It's a strip that's soaked in water, glycerin, and oxalic acid, and you put it into your hive. It is in there over the relatively long treatment period, and the mites are going to wind up getting exposed to the oxalic acid and killed. That's what we want to have happen to them.

Becky: David, do we have somebody to thank for getting this formulation figured out?

David: That's interesting. The VarroxSan is the product that's currently available. It's manufactured actually in Uruguay, and it is the only product currently registered in the US, although there are some others in the pipeline that are probably going to be showing up in the next few years. The VarroxSan product is really in many ways based on, or grew out of, the Aluen CAP product, which was developed in Argentina.

That product is also an extended-release oxalic strip soaked into fiberboard strips with glycerin and water and all that mixed into it. That is what actually inspired Randy Oliver in a lot of his research on extended-release oxalic acid strips soaked into various substances. There have been various investigations and efforts that have tried to find ways to expose oxalic acid to Varroa mites in a slow, controlled, time-released way that passively releases it within the hive in a way that isn't disruptive to the bees or the brood. VarroxSan is the first one to make it onto the US market.

Jeff: Let's step back real quick. What is oxalic acid?

David: Oxalic acid is an organic acid. It's a small molecule. This series is all about different miticides. It is useful to know that a formic acid molecule and an oxalic acid molecule are very, very similar. Basically, if you take two formic acids and stick them together, now you've got an oxalic. The oxalic acid is a product or a chemical that is found in nature. It is naturally found in honey plants. If your bees are visiting sumac flowers or rhubarb flowers, oxalic is what makes rhubarb taste sour. It is going to be harmful to the mites, but it is something that bees naturally encounter. Their bodies are capable of dealing with a little bit of oxalic acid, which is what makes it a really good active ingredient for this miticide.

Becky: Before anybody puts rhubarb in their colony.

David: Oxalic acid is the active ingredient, but it's important to understand that you should only be using these registered, approved, tested, proven-to-be-effective miticides in your bees. Grabbing some oxalic acid-rich rhubarb leaves and throwing those on top of your top bars is not going to solve your mite problem. Folks have tried, folks have tested it. It doesn't work. It's nice to imagine, but there's a little more oxalic going in in these strips than you would find from your bees visiting a sumac flower that day.

Jeff: These strips go in, that's a fiberboard that is bendable, and it drops down between frames. Is it on every frame, or how do they recommend that you put the oxalic acid strips?

David: Applying VarroxSan to your hive is described clearly on the product label the dosage that you're supposed to use. The recommendation is that for every two and a half frames of bees in your colony, you should be using one strip. You really get to choose where you put it between the two and a half or so frames that it's supposed to be treating. The idea is that it just needs to hang down in between the frames so that your bees are going to be every once in a while bumping into it.

You need to have this oxalic glycerin water mixture, this wet mixture of oxalic acid occasionally getting onto bee bodies so that it occasionally gets bumped into the Varroa mites, and then it kills the Varroa mites from there. 2.5 strips per frame of bees in your brood chamber.

Becky: How long do we leave these strips in the brood chamber, David?

David: It's a long treatment. The idea is that it needs to be there long enough for multiple cycles of brood to get capped over, emerge, and then new brood to be capped, and new mites that were protected under those caps to emerge and bump into the oxalic. The application period is between 42 and 56 days. They've very nicely given us a little wiggle room there, but essentially what we're talking about is a month and a half to about two months of treatment with these strips. Often because these are just fiberboard or cardboard strips, the bees will wind up chewing them up and removing them from a really strong hive before the end of that treatment period. There's nothing to panic about if that happens.

Becky: It's a long-lasting or long-acting miticide, but it also does give us some quick knockdown of the mite colony or the mite populations, doesn't it?

David: That's right. The manufacturers have advertised this as being good at knocking down high mite levels and also good at holding mite levels down that are already under control, but that you want to keep under control. Independent research done on this product and similar products all over the country and all over the world has shown us that it really, really does seem to be quite good at holding mite levels under control. Its ability to knock the mite levels down hasn't been proven as reliably.

There may be different circumstances where some studies found one result and some found another. Yes, it can be used to knock down mite levels, but it's extremely good when your mite levels are under control at keeping them under control instead of allowing them to balloon up again like they normally would.

Jeff: David, how does the oxalic acid actually work against the Varroa? How does it kill it?

David: What a great question. I wish I could answer it, but I can't. [laughter] The reason is we don't genuinely fully understand why it is that oxalic acid kills Varroa mites. Some people have suggested that because the mites have a thin and almost damp, moist footpad that they use to stick onto the bees and stick onto the comb, that that interface might allow little bits of oxalic acid to dissolve into the mites' bloodstream and kill them. We've looked for evidence of that, and we don't have clear enough evidence to say definitively that's how they're doing it.

We aren't really sure how it kills mites, which is one of those amazing truths of bee research that we can all be using oxalic in our hives, we've been using it for years, it's a big part of how we keep our mites under control, and we still don't really know what's going on. I currently have a research project underway. It's being led by Professor Lewis Bartlett at the University of Georgia, but he, Frank Rinkevich, who's another Varroa scientist working at the USDA, and myself, we're all sitting around debating what we thought the Varroa were experiencing when they get killed by oxalic acid, and we couldn't come to any agreement.

We designed the experiment on the back of a napkin, and Lewis currently has a graduate student pursuing that. We're going to try to get some information about what's going on, but the answer at this point is, we know it works. We're not really quite sure how, but it seems to do a pretty darn good job of killing mites and not killing honeybees.

Becky: It's considered organic, isn't it?

David: Yes, it's an organic acid, which is the classification of the kind of acid that it is. Whether it's going to allow you to get a certified organic label on your honey or not is a very different question. It falls within what are often considered the organic or more natural Varroa control technologies. That's going to be your essential oil-based treatments and your organic acid-based treatments. Again, this is a molecule that is found in nature, it is naturally present in bee colonies.

We're boosting those levels a little to kill the mites. It's very different from something like a synthetic miticide, which is a laboratory-produced chemical, which is exquisitely designed to go right in and target the Varroa mite and kill them but isn't going to be a molecule that bees would otherwise have encountered in nature.

Jeff: Let's talk about the benefits of using oxalic acid through VarroxSan and similar products. It sounds like one of them, and we touched on it, is that you can use it while the honey suppers are on.

David: That's right. It is important to note that on the product label, you don't want to put this onto a colony, and then throw your honey supers right on top. It says very, very clearly that there should be a box in between where the strips are and where your honey suppers are. That's to prevent the oxalic acid or even the glycerin from getting into honey that you're then going to extract and consume or sell to somebody at a farmer's market or something like that.

You do need to make sure you've got a spacer. It might be a brood box that doesn't have any strips inside. It might be maybe a box where you've got your bees drawing out comb, but you're not planning to harvest that honey, but then the honey supers above are perfectly safe. That's because the regulators have decided that there is no level of oxalic acid that could get into honey from one of these treatments which is higher than the level that would be encountered just by having your bees forage on a lot of sumac flowers.

There's not any real risk of "oxalic contamination", but you do still need to follow the label instructions there. Yes, a great advantage is that I can put this on my colonies, put my supers on, make my honey crop, and be keeping my mite levels under control. I really see the value of VarroxSan as a Varroa mite hold-down treatment when I have few other options available to go in and actually try to control my Varroa population.

Becky: David, I know some beekeepers who will have their bees in the brood box, and then that first super is always left for the bees for winter. That would be a way to apply the VarroxSan in the brood box, but let that second deep bee or super go back to the bees.

David: Yes, exactly.

Becky: That would be another way to do it, right?

David: Exactly. The point of it is simply that supers that you are intending to harvest honey from for human consumption do have to have that one box separation from the strips. I think that's probably out of a great abundance of caution that that's even on the label in the first place.

Becky: As far as possible cons for VarroxSan, I do know that when you go into your colonies and you look behind the strips, it is common to see that the comb will be chewed down behind where those strips were, and it's going to have a negative impact on some of the brood that's really close to the strips. I see it as variable, but that's something people should expect, right?

David: Right. Absolutely. Even if the total number of brood that are killed are an acceptable loss, you also have to consider the surface area. If every strip's width has a little area underneath it where the queen now can't lay eggs, now I've got a brood nest that's slightly smaller than it was if she had full reign of every single frame. That's not to say that it's a bad treatment, but it is important to understand that, yes, you're limiting the real estate and also not doing any favors to the brood that are closest to those strips.

Becky: I think it's a good lesson, too, because the strips look really safe and people might not think anything of it, but it is a pesticide that we're putting into the colony, and so you should--

David: Wear your gloves when you're putting it on. It does have downsides. Each of these things is-- We're introducing a chemical stressor to our bees. We are knocking the bees outside of their equilibrium, but we're giving them something that will help to kill the Varroa mites, which on balance is always going to be better. I think for VarroxSan, the biggest con that I might talk about, the biggest downside, the biggest consideration that might make me not reach for it is that it does not seem that it is as well-supported to use an extended-release oxalic strip like this when you've got a really high mite level.

When your mite levels have gotten away from you, and they've gotten out of control, this would not be my first line of attack against them because it is sort of a low-and-slow treatment. It may gradually bring the mite levels down, but sometimes I just want to punch those mites right in the face. It seems like VarroxSan is sort of a kinder, gentler treatment, but that means that you don't want to use that in the middle of a catastrophe, or at least the evidence I've seen so far is mixed on whether or not it's ready for that job.

Becky: I'm wondering if we're going to make listeners wait to hear what that punch is going to be that you would use for another episode, or if you want to do a teaser.

David: I think they'll have to listen to one of the other episodes, and they'll just have to see if that's the one that I think is a good punch in the face for Varroa mites.

Jeff: Just for planning purposes, David, which product would that be so I can plan it out on the episode?

Becky: Wait, are you going to ask for a friend now, too? David, as far as cons go, are there temperature restrictions for the use of VarroxSan in the colonies?

David: Sort of yes and no. The label doesn't specifically say you can't use it above or below these temperatures, but it is important to remember the way this strip works. You need to have the bees bumping into the strip and getting little bits of the active ingredient on their bodies. If you hang the strip all throughout your brood box, and then your bees go into their tight winter cluster, then they're not going to be bumping into the strips on the outside edges, and so the mites aren't going to get exposed.

The recommendation from the manufacturer, the label instructions say that this is a spring, summer, and/or fall treatment, but that it isn't something you would want to reach for in a winter, at least not a cold winter, when the bees are going to be separated from those strips as the winter cluster moves around inside of that box.

Becky: Jeff, I know that you used VarroxSan recently, or not even recently, you used it a little bit ago. What did you do as far as not forgetting for when you have to take out those strips? Because I think that could be a con as far as when did I put those in.

Jeff: Well, you have to have good hive notes. I do keep notes, and then I was diligent because I know how well I remember things or don't, that I actually put that evening after I got back from the bee yard, I put on my calendar, "Remove strips." I did that. For the first round, the other colonies that I set up, I put in strips, and then I forgot to put the date down, but I have approximate days that I need to put that on there. It is a task, and you have to keep after it.

David: It is nice to know that, because the label says put it in for 42 to 56 days, it's clearly not a really, really tight-- if you're a day or two late, you're probably not going to get yourself in any big trouble.

Jeff: I can tell you, after 56 days, the bees do chew them up significantly.

David: There may not be much strip left. These may remove them for you.

Jeff: Yes, they do.

Becky: I was surprised. I visited them about a week after putting them in, and I have some colonies that are well on their way. I might not have to take them out. They are well on their way to getting rid of them.

Jeff: Where they didn't remove them was across the top of the frames.

Becky: Okay. Interesting.

Jeff: Well, this has been an exciting topic, Varroa treatment. I'm like you, Becky, I like to kill mites. David, you like parasites. I know you have conflicted feelings.

David: I study parasites, and I appreciate their interesting biology. No, I'm a beekeeper too, and I sure like killing Varroa mites.

Jeff: I know. Well, thank you, David. Thank you, Becky, for joining us on this exciting series of Varroa treatments. Look forward to the next one.

David: It's been great talking about killing mites with you.

Becky: Exactly.

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