Oxalic Acid Dribbling

The Idea

Varroa mite. Photo courtesy of Scott Bauer of the ARS.

Dribbling oxalic is a non-contaminating, relatively safe, and cost effect varroa mite treatment. It is quick to apply and can be used when hives can be opened.

The Details

Why Dribble It?

It’s a safer way to get oxalic into a hive when the conditions are right.

  • no fire danger
  • no errant fumes

Formulation Basics

Accuracy is required. For some reason, oxalic acid solutions are much harder on the bees than are the oxalic fumes. It’s imperative to get the concentrations right. And to apply them correctly or the bees will suffer for it.

A good scale is required to accurately prepare the oxalic solution. I purchased one from Americanweigh. And was pleased with their selection, price, and service.

European Formula

The Europeans have decades more experience dribbling oxalic acid than anyone else.

They recommend preparing a basic 1:1 sugar solution by dissolving 1 kilogram of sugar in 1 liter of warm water resulting in 1.66 liters of sugar syrup. Then stir 75 grams of oxalic acid into the sugar syrup until dissolved, yielding a 3.5% oxalic solution.

Canadian Formula

The Canadians have done more formal recent research and have approved it for use. Be sure to read the Canadian label before dribbling. It states the formulation and the safety requirements.

They recommend 35 grams in a liter of 1:1 sugar syrup by weight or volume.

Formula Differences

A difference exists between concentrations in the two recommended formulas after adjusting for the differing volumes. It appears this difference results from the different molecular weight of oxalic acid and oxalic dihydrate, the most commonly available form.

Allen Dick has a webpage discussing these differences.

Be sure to check which kind of oxalic you have and adjust your formulation.


How to do it

  • read the Canadian label
  • use the appropriate safety gear
  • dribble 5mls of acid solution between each set of frames completely occupied by bees
  • put the solution right on the bees
  • use less for partly occupied frames
  • don’t put more than 50ml of solution in one colony
  • don’t treat more than once a season if bee flight is restricted

When to do it

Dribbling works best when the hives are broodless.

Reports show two treatments, one late fall and another early spring, are OK if the bees can fly.


Beekeepers are an inventive bunch. And equipment abounds for getting the oxalic solution into a hive.

A beekeeper with a few hives is at an advantage. He can take his time. Individually evaluate a hive. And use simple equipment to safely and accurately apply the correct dose. A simple plastic bottle, marked in 5ml increments, is all that’s needed. Or an appropriately sized veterinary syringe would work as well.

Automatic syringes , homemade sprayers, etc. are commonly used by beekeepers with many hives to treat. Problems abound with most of this equipment.

  • oxalic acid corrodes seals
  • solution under pressure can erratically spray or leak
  • it’s hard maintain an accurate dose with changing pressures or temperatures
  • multiple head sprayers treat all hives the same regardless of bee population

I suspect that the problems experienced by some commercial beekeepers while dribbling oxalic result from improper application.

Have your own design? Just be sure safety and accuracy are at the top of your design criteria.


The oxalic solution has about a two week shelf life at room temperature. If it turns color or is older, mix up another batch.

Any excess solution can be refrigerated or frozen almost indefinitely. But it’s probably best to get rid of it. The risk that someone might inadvertently get poisoned with it while it’s stored in the refrigerator, far outweighs any cost savings. Were talking tenths of pennies per hive here!


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4 Responses

  1. maria says:

    Dennis. Forgive me. Isnt this stuff highly toxic? Also, I know you know Sam and Kirk. They don’t do any treatments for the mites or for anything for that matter.
    Should we be treating with antibiotics and such? I thought the idea in natural beekeeping is to let the bees develop their own immunity. I am confused. Also, I do not feed my bees sugar, I feed them back honey I save for them or take from another hive. Having them build their own comb is essential in treating a lot of the ailments found in bees as well.

    • -bW says:

      Hi Maria

      These are good questions and controversial ones as well. 🙂 I will approach it from bottom up. I hope neither to confuse or disappoint you. But here’s my take on it. There’s lots of room for different approaches.

      Feeding? Feeding bees back their own honey is the best solution. It’s much better than sugar which I think is better than corn syrup. But what if the bees are short of feed and the beekeeper is short of honey? Should sugar be used? Or if sugar is too expensive, what about corn syrup? Would it be better to just let the lazy colonies die and split off the few hard working survivors? What happens when a beekeeper has only a few hives and they are all starving? Would a dead hive of naturally starved bees be better than a living hive of artificially sugar feed bees? For some yes. For others no.

      Treating? Never routinely or prophylactic or with anything that would contaminate the hive. But when absolutely needed for life, absolutely treat! It’s not always the best or most immune bees that survive. Sometimes it’s just the luckiest. Nature does select for a balance but has little regard for the survival of an individual bee or colony. Those processes work on a larger scale and over a long time frame. Sometimes it’s necessary to intervene and re-establish a natural balance when things get out of wack.

      Do you know of any beekeepers who would deny themselves, their spouse, child, or even the pet dog antibiotics when needed? Would they deny their bees the same? Why?

      Finally oxalic acid. It’s the most effective, non-contaminating, least toxic mite treatment I’ve ever tried. And using it to treat mites is the best option I know of when moving hives from a less than natural state to natural beekeeping. It takes times for the bees and mites to come into a kind of equilibrium. And dead hives never reach that state.

      I think, if a beekeeper only has a few hives, it’s better to keep them alive if treatment is needed and then change their genetics with one of Sam’s or Kirk’s queens than it is too start over from a dead hive.

      Just some thoughts, Maria. What do you think?


  2. Natalee Thompson says:

    Hi Dennis,
    Do you still stand on your opinion of oxalic acid treatments? I used Hopguard last year and the results were ok. It was easy to use but pretty expensive if you only had 1 or 2 colonies to treat. What are your requirements for treatment?

    • -bW says:

      Hi Natalee

      I’ve haven’t treated enough, since going natural, to know much about the newer mite treatments. I simply haven’t followed them.

      Oxalic is effective, non-contaminating, easy to use, and cheap. And I’ve got a few pounds of it which will last a lifetime.

      Requirements? It’s a subjective feeling based on a decade of bee observations and mite counting in a untreated beeyard. A colony’s ability to tolerate mites/viruses varies greatly depending upon mite load, bee genetics, and colony stress.

      Equating dropped mites with mite load isn’t as easy as most think. Some colonies can carry a tremendous mite load, without symptoms, and then suddenly collapse. My Russian bees were like that. Others will carry a small mite load with lots of symptoms. Hence the problem with setting threshold mite drop values.

      I no longer count mites. But it’s a good to do a little counting until the necessary experience is gained.

      Some things to look for: mite fecal deposits, deformed wings, crawlers, mites on drone brood, and phoretic mites.


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