In my previous blog post, I discussed oxalic acid – a great Varroa mite treatment for our beehives. It’s a substance found in nature, effective in killing mites, but safe for our bees when used correctly. The question now becomes – how do I use it safely and effectively?

First it is important to understand that it only kills the phoretic mites. These are the mites attached to adult bees or crawling around the hive. It won’t kill the mites that have made a home in the brood cells. This is why oxalic acid is most effective when there is little or no brood (winter time!). The acidity of the oxalic acid is 70 times as toxic to mites as it is to adult bees, which makes it a deadly weapon to the awful mites, but safe for the bees when used in the correct dosage. Now you might ask – what is the correct dosage?

The dosage I use is for the “dribble method” (which I will describe how to apply in detail in the next blog). This method is the safest for the beekeeper applying it, as there is no vapor created that can be damaging to our respiratory systems. Further, this method requires little equipment and is easy to apply, which makes it great for a hobbyist beek like me!

You can buy oxalic acid online through Brushy Mountain Bee Farm for the incredibly cheap price of $6. Even better, you can buy a full application kit  for just $12. The amount of oxalic acid in these kits will treat 20 hives!

Next you want to mix it accordingly. Remember, oxalic acid is 10,000 times stronger than acetic acid in vinegar and is caustic. It can affect the eyes, skin, and respiratory system. Therefore, it is important to use caution when mixing it and applying it. This is where the $12 kit above comes in handy. Further, mixing it to the correct ratio (2.8% oxalic acid to sugar syrup solution) is key to ensure that you kill the mites without harming your bees. The label on the product instructs you how to mix the entire quantity to treat up to 20 hives. I only have two hives at home and help the Boise State students with their four hives. So, I prefer to mix it in smaller batches so that I can have some left for next year. It will keep indefinitely in an airtight container in a cool room.

Here’s how I mix it:
1 cup of sugar syrup created by mixing 1 cup hot water and 1 cup granulated sugar.
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8.4 grams of oxalic acid measured accurately using a scale.
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This results in enough treatment for four hives, giving each the required 50 mL dosage.

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It is important to use a scale to ensure that you measure 8.4 grams accurately.

The next step is to mix the oxalic acid with the sugar water. I used an old plastic bottle that I could fit my syringe into for application. I took a folded brochure and carefully funneled the oxalic acid into the warm sugar syrup and swirled it to mix thoroughly. I want to make a special note that is important to wear protective gear when handling this product. In my next blog post, I will discuss how to effectively dribble this mixture into your hive.

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Oxalic acid was recently approved for use in the USA. I encourage you to read up on it! The EPA’s registration decision document has valuable information that I found surprisingly easy to read. Jennifer Berry, from the University of Georgia, has a neat article on her introduction to the use of oxalic acid and its process of getting approved by the EPA.
Finally, the approved seller of oxalic acid, Brushy Mountain Bee Farm, has a great Q&A article that will answer most of you basic questions.

Loving, caring, and keeping your bees requires that you know what you are doing and putting into your hives. The more I know about oxalic acid, the more comfortable I am with using it. Check out my next blog on how to apply it!

Keep your bees buzzin’ y’all!

  • BoiseBeeMan

    Dang! Beeks – pay attention to this one. Well researched, well written and SPOT ON!
    Well done, Ms. Melinda, well done!