Oxalic Acid Calculator

On my previous post “Nuc Calendar Generator”, I wrote about a spreadsheet program that I created in order to help us quickly generate a calendar with all of the necessary information that we need to aid us in making our nucs. At the end of that post I mentioned that I would be writing a follow up post to tell the story behind the “Oxalic Calculator” tab. So without further ado, here is story:

Soon after I had finished my Nuc Calendar Generator program, I was invited by a friend to attend a social gathering. During this gathering, I ran into a gentleman that mentioned that he was making mead (honey wine) for his brother’s wedding. Being a mead maker myself, we struck up a great conversation. The conversation soon transitioned to beekeeping after he mentioned that he would like to keep his own bees to make mead using his own honey. He had already done a lot of research on bees, so he was full of questions. Of course, being a “treatment free” beekeeper, I had to give him my thoughts on treatment free beekeeping and why its the best approach for a hobbyist (in my humble opinion). During that entire conversation, I noticed an elderly gentleman (that neither of us knew) that was “hanging around” listening to our conversation, so we asked him to come join us. It turns out that the elderly gentleman was a retired beekeeper (that still kept several hives “just to stay busy”). He immediately corrected me on why it was so foolish to be treatment free. After all, he had ran a business for years keeping happy bees with the good old (over) treatment method. I respectfully disagreed, but we did have a good conversation about the advantages and disadvantages of treating bees, specifically for varroa. It turns out that this gentleman had used a varroa treatment for his bees (and still treats his current ones) using a chemical smuggled in from Mexico, as it is illegal to use and purchase in the US. He didn’t give me the name of it, because he couldn’t remember, or at least that’s what he said.

I have much respect for old-timer beekeepers and when I am fortunate enough to speak to one, I always try to learn from them. This particular beekeeper left me thinking about something. He said that when you have lots of beehives in one location, sooner or later you’ll have a varroa outbreak that will take out most of your bee yard. After all, having such a high concentration of hives in one area is not natural. He mentioned that not having a backup treatment plan is just plain foolish. On that point we could both agree. In past years, before we were in the almond pollination business, we weren’t afraid to lose bees to varroa. It’s how we ended up where we are today with very good survivor bees. However, we are now in a position where we must deliver a specified number of hives to our almond grower. This year, it means that we can only afford to lose about 8% of our bees and still meet our target. As a smart business decision, we should have a backup plan.

I personally don’t like to take medicine, although I’m not opposed to it either, and I will certainly take any medicine in a life and death situation. I think that I feel the same way about bees now. We need to have a backup treatment plan in case we ever experience a severe varroa outbreak that represents a life and death situation for our business.  I’ve thought about this before and I’ve even done some research on the best “organic” treatment methods but haven’t really taken any actions. I’ve decided in the past that if I had to treat with something during an emergency, it would be Oxalic acid. It’s not as effective as the hard chemicals because of the small residual time and the fact that it won’t kill mites present inside the capped brood. However, it can be pretty effective especially if you treat during broodless periods, and the best part is that it is an organic acid (like citric acid).

Well, since I had just finished making a Nuc calendar generator, I figured why not make an Oxalic calculator as well? If you are going to treat by using vaporized Oxalic acid then you don’t really need a calculator. I suppose that vaporizing Oxalic acid is a good way to go if you only have a few hives, but it can be slow and time consuming and the vapor is hazardous if you inhale it. For these reasons, I would use the liquid sugar/Oxalic dribble method instead. With this method you can make a big batch and treat as many hives as you need to fairly quickly and the solution is safe to handle. If you want to read more on the Oxalic acid treatment methods, I recommend reading the articles on the subject written by Randy Oliver on his website.

If you are going to use the liquid sugar/Oxalic mixture, you will need to follow a specific recipe. How strong you want the mixture will determine what recipe you follow. Also, the recipe changes if you are using wood bleach (diluted Oxalic acid used for commercial applications) or pure laboratory grade Oxalic acid crystals. Lastly, when following the recipe, you will need to make sure that your measurement units are correct (as everything needs to be weighed). There is a specific range of treatment where Oxalic acid is effective. Too little and it won’t kill mites and too much and it will kill your bees, so you need to be careful to get the mixture right. I’m the “measure twice cut once” kind of guy, except in this case its “get the calculations right once and use them forever”.  With this in mind, I created the “Oxalic Acid Calculator” and included that into the Nuc Calendar spreadsheet. This way if we ever need to treat, I can pull up the calculator and quickly generate a recipe without having to do lots of research.

Like I mentioned, treating with Oxalic acid is most effective if done during a broodless period when all of the mites will be exposed to the treatment. When you create nucs, you are making a broodless period between the time that the last eggs from the old queen hatch and the new queen’s larvae are capped. If you wanted a “clean” start to the nuc colony, it’s a very good time to treat them. For this reason, the Nuc Calendar Generator also provides the best dates to treat the nuc, reference Figure 1 below:

Figure 1: Treatment window shown in the Nuc calendar


To end this post, I will describe how the calculator works:

You go to the “Oxalic Calculator” tab. Then you go to the “Input Parameters” section (at the very top) and select your four input parameters. Your options for mixture strength are Strong, Medium, and Weak. The options for Oxalic type are Pure and Wood Bleach. The number of colonies is simply how many colonies you wish to treat (at a dose of 50 ml per colony). The last input parameter is to select large units or small units. Large units are Kilograms (kg), Pounds (lbs), Liters (l) , and Gallons (gal). Small units are grams (g), Ounces (oz), milliliters (ml), and quarts (qt). I included this feature because if you are making a small batch, you likely don’t want to see 0.062 pounds. You are going to be measuring in ounces. The inverse of the same concept applies to large batches. I find the metric system to be much easier, so I use metric personally, but I included the US standard units for those who like harder math conversions. Reference Figure 2 below:

Figure 2: Input parameter of the Oxalic acid calculator

Once you’ve entered the inputs into the calculator, you can find the recipes in both metric and US standard units, reference figure 3 below:

Figure 3: Oxalic recipes in metric and US standard units

The page can easily be printed for your records. It might look something like what is shown in figure 4 below:

Figure 4: a printed Oxalic calculator form with notes.


I’ve already tested the calculator by creating a batch of medium strength Oxalic solution and treating 10 hives. The results were inconclusive as I didn’t have any baseline varroa counts prior to treating. However, after 48 hours, I inspected the hives and found a few dead varroa mites on the bottom boards. The most that I counted was around 10, but I suppose that the bees could have removed some as I wasn’t using sticky boards (I have never actually used a sticky board). At the very minimum the solution killed mites and didn’t kill bees, which is a good sign. I used the treatment tables provided by Randy Oliver (very knowledgeable in Oxalic acid) to calibrate my formulas, so I am confident that the calculator will work as intended.

Well, it took an unexpected run-in with a retired beekeeper to finally  motivate me to get in motion with a backup treatment plan for varroa. Our long term strategy will never change as we firmly believe that the best plan to fight varroa is breeding bees that fight varroa (I’ve documented this in previous posts). But in a pinch, we now have a viable backup plan.


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