We all know how crucial it is to manage varroa mites effectively, but did you know that some acids can be your best allies in this battle?

Today, we’re exploring the science behind OXALIC ACID and FORMIC ACID — two naturally occurring acids that can make a big difference in your hives.

Natural Sources of Oxalic and Formic Acid

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Oxalic Acid: This compound is abundant in nature, found in plants like spinach, rhubarb, and even honey. It’s not just a culinary ingredient; in the hive, it becomes a potent tool against varroa mites.

Formic Acid: Naturally occurring in honey bee colonies, formic acid is found in plants like stinging nettles and is even produced by ants. Its presence in nature makes it a familiar substance to bees, which helps minimize any negative impact on the hive.

Why These Acids Are Safe for Bees

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Both oxalic and formic acids naturally occur in the environment and within the hive. This natural presence ensures that these treatments do not introduce foreign or harmful substances to your bees when applied correctly. Additionally, neither acid leaves behind residues that could contaminate honey or wax, preserving the purity of your hive’s products.

There is discussion about strong concentrations of these harming bees or the queen. Still, much of this involves using the right concentration at the right temperature and following manufacture directions (see info below).

Mode of Action: How Do These Acids Work?

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Oxalic Acid: When used as a vapor or dribble, oxalic acid works by forming tiny crystals that attach to the mite’s legs—specifically to the adhesive parts known as pulvilli. These crystals eventually lead to the mite’s death within hours. Interestingly, studies, such as those conducted by Gerhard Brüning, have shown that oxalic acid penetrates the mite through its feet, irrespective of whether it's applied as a vapor or liquid. This action does not harm the bees, making it a safe treatment option.

Formic Acid: Formic acid’s standout feature is its ability to penetrate the brood cap, where most varroa mites reside.

This is a critical advantage, as it allows the acid to reach and eliminate mites in all stages of their life cycle, including those hidden within the capped brood. Formic acid vapors spread throughout the hive, effectively targeting both mites on adult bees and those under the brood cap.

Temperature Dependency and Application Timing

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Oxalic Acid: Works best in cooler temperatures, ideally when the bees are clustered. This makes late fall or early winter an optimal time for treatment, particularly when there is little or no brood in the hive.

Formic Acid: This acid requires careful temperature management, performing best when daytime temperatures are below 85°F (30°C). High temperatures can increase the risk of bee mortality, so it’s essential to monitor weather conditions during treatment.

Effectiveness Against Mites Under Cappings

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Oxalic Acid: While oxalic acid is highly effective against phoretic mites (those on adult bees), it does not penetrate the brood cap, so it’s less effective against mites inside capped brood cells. However, ongoing research, including our own experiments, is exploring how oxalic acid might be distributed through bee vectoring, potentially reaching mites in hidden areas.

Formic Acid: One of the few treatments that can kill mites under the brood cap. The ability of formic acid to penetrate the brood cap is a game-changer, ensuring that even the mites hiding in capped cells are not safe from this treatment.

Practical Tips: Using ProtectaBEE® with Acids

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Formic Acid: When using ProtectaBEE® with formic acid, it’s important to remove all inserts during the treatment period to allow proper airflow and prevent any buildup of the acid that could harm the bees.

Oxalic Acid:  A vaporizer can be easily inserted into the back or side of the hive, and solid inserts can be used to seal the hive, making the process quick and straightforward.

With a wand vaporizer, simply add a solid insert to one drawer and slide the wand through the other drawer adding a wet rag around the wand to keep in the vapour (see photo above).

With an Oxalic dribble the opening can remain the same as before treatment.

Research Insights and Ongoing Experiments

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Oxalic Acid: Besides bee vectoring with entomopathogenic fungi, we are also currently testing a new slow-release oxalic sponge placed at the hive entrance. This method aims to utilize bee vectoring, where incoming foragers possibly carrying mites come into contact with the oxalic acid and spread it throughout the hive.

Our preliminary results have been promising, showing that mite levels were maintained rather than increasing—an encouraging sign that this method could be an effective new tool in the fight against varroa.

We’ve drawn on the work of researchers like Randy Oliver to refine our approach to varroa management. Oliver’s data has highlighted the importance of early treatment to prevent mite population surges.

Our own experiments, such as the use of the slow-release oxalic sponge, are ongoing, and we’re excited to share our findings with you as they develop.

Conclusion

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So, yes—Bees on Acid might sound like a wild concept, but when it comes to oxalic and formic acids, it’s a proven strategy for keeping your hives healthy. Stay tuned for more updates by following us on Instagram and Facebook!

Bee well,

Dr. Erica