Oxalic Acid for Bees: What's Legal, What Works, and Why We Sell EZ-OX

Oxalic acid is the most widely used varroa mite treatment in American beekeeping, and it is also the one most often bought wrong. This page covers what oxalic acid does to mites, which products are legal to put in a hive, the three ways beekeepers apply it, how much to buy, and why we sell EZ-OX rather than the off-brand powder that shows up when you search for it.

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What Oxalic Acid Does to Varroa Mites

Oxalic acid is a naturally occurring organic acid found in rhubarb, spinach and honey itself. Applied to a colony as a vapor, a syrup dribble, or a slow-release strip, it kills Varroa destructor mites riding on adult bees while leaving the bees, the brood and the honey essentially untouched. It has been used in Europe since the 1980s, was registered by the EPA for US use in 2015, and received a federal tolerance exemption in 2021 that acknowledges it leaves no meaningful residue in honey.

It has one hard limit that every beekeeper should understand before buying it: oxalic acid does not reach mites sealed under capped brood. No vaporizer, no dribble, no brand changes that. A single treatment is most effective when the colony is broodless. When brood is present, the mites under the cappings emerge over the following weeks, which is why beekeepers treating in summer run a spaced series rather than one shot. Our Broodless Window Finder estimates when your colonies are most likely broodless, and the Treatment Series Planner builds the schedule when they aren't.

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Which Oxalic Acid Is Legal for Bees

Oxalic acid used to control mites is a pesticide under federal law (FIFRA). That means it is legal to apply in a hive only if the specific product is EPA-registered for that use and you follow its label. The USDA bee lab's own FAQ says it plainly: wood bleach, chemical-supply oxalic acid and oxalic-acid-rich plants are "not registered products," and using them is a label violation subject to enforcement. In February 2024 the EPA went further and issued an advisory reminding beekeepers that using unregistered oxalic acid, amitraz, formic acid or thymol in hives violates FIFRA and can make the honey legally adulterated.

As of this writing, two oxalic acid products are registered for use in US beehives in powder form:

A third registered product, VarroxSan (EPA Reg. No. 94413-3, registered December 2023), is an extended-release oxalic acid strip rather than a powder; more on it below. The head-to-head on the two powders, including residue photos and the excipient question, is in Api-Bioxal vs EZ-OX.

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Why We Sell EZ-OX and Not the Off-Brand Stuff

Search "oxalic acid for bees" and half the results are unlabeled powder — wood bleach, rust remover, "99.6% oxalic acid crystals" in a plain bag — sold by people who never mention a hive because they legally can't. It is usually a few dollars cheaper than EZ-OX. Here is why we don't sell it and won't recommend it.

It's illegal in a hive. Not a gray area. An unregistered pesticide applied to a food-producing colony violates FIFRA, and the EPA has said it can render the honey adulterated. A few dollars saved on acid is not worth a crop you can't sell.

You don't know what's in the bag. Industrial oxalic acid is made and packaged for cleaning and bleaching, with no requirement that it be free of heavy metals or process contaminants. EZ-OX is registered as 97.0% oxalic acid dihydrate, and the registration means the EPA has reviewed what the other 3% is.

It's made here, by a beekeeper. EZ-OX is registered to and produced by Mike's Bees LLC in Cambridge, Ohio, a small veteran-owned company. When we have a question about the label, we call a person who keeps bees. That is not something you can say about a chemical repackager, and it is not something you can say about Api-Bioxal either, which is made in Italy and distributed through a French pharmaceutical company.

It burns clean. Api-Bioxal's formulation includes a glucose carrier that beekeepers on both sides of the Atlantic report caramelizing in the vaporizer chamber into a black, charred deposit that has to be scraped out. In a vaporizer that cycles every 10 to 30 seconds, buildup in the chamber changes how the acid heats and how much reaches the bees. EZ-OX is essentially pure oxalic acid dihydrate; the bowl comes out clean, treatment after treatment.

It's cheap anyway. Roughly 12 cents per 2 g dose from the bag and 10 cents from the bucket. Api-Bioxal is about 31 cents. With oxalic acid, the acid is never the expensive part, so there's no reason to pay two and a half times more for a product that gums up the chamber, and no reason to break the law to save a nickel.

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Three Ways to Apply Oxalic Acid

The EZ-OX label covers vaporization and dribble, plus a spray for package bees. Extended-release is the third method beekeepers use; read that section carefully, because the label situation is different.

1. Vaporization (sublimation)

This is what we do in our own yards and what most of this site is about. A vaporizer heats 2 to 4 grams of oxalic acid to about 315°F (157°C), where it sublimates into a gas that fills the hive and recrystallizes on the bees and the comb. Mites on adult bees die over the following days. The powder label rate is 4 g per deep brood chamber, and 4 g per deep box is the maximum legal dose. What we recommend and run in our own yards is 2 g per brood box — 2 g for a single deep, 4 g for a double — stepping up to the full label rate for a heavy infestation; the reasoning is in how much oxalic acid per hive. Seal the entrance, vaporize, and keep the hive closed for 10 minutes.

Why beekeepers prefer it: the hive stays closed, so there is no disturbance and it works in cold weather when you can't open a colony; a treatment takes 10 to 30 seconds with a cordless unit; and the vapor reaches every surface in the box. The gear is a one-time purchase, which is where the InstantVap oxalic acid vaporizers for bees come in, but the acid works in any vaporizer — ProVap, Varrox, Varrox Eddy, or a pan-style wand. Wear a NIOSH-approved respirator with acid-gas cartridges; the vapor must never be inhaled. Step by step: how to use an oxalic acid vaporizer safely.

2. Dribble (trickle)

The no-equipment method. Per the label, dissolve 2 g of EZ-OX in ¼ cup (59 ml) of 1:1 sugar syrup, then trickle 5 ml into each occupied seam between frames, to a maximum of 50 ml per colony. Bees distribute the syrup through the cluster and the acid contacts the mites. All you need is a scale, a syringe and the powder. It costs the same 12 cents a dose.

The trade-offs: the hive has to be opened, the syrup is hard on bees if it's applied more than once per brood cycle, and it does nothing for mites under cappings, so it is really a broodless-colony treatment, best in late fall or winter on a mild day, or on a freshly hived package or swarm. In a colony full of brood, one dribble is not going to fix a mite problem.

3. Extended-release (strips, sponges, shop towels)

Extended-release oxalic acid mixes the acid with glycerin on a cellulose carrier laid across the top bars, where bees contact it continuously for several weeks. Because it stays in the hive through a full brood cycle, it catches mites as they emerge from the cappings, which is what makes it interesting for summer treatment with brood present. Randy Oliver's work at Scientific Beekeeping is what put it on the map.

Here is the part to read twice. The only EPA-registered extended-release product is VarroxSan, a pre-made cardboard strip. Homemade pads — sponges or shop towels soaked in oxalic acid and glycerin — are widely used and widely discussed, but they are not on the EZ-OX label or the Api-Bioxal label. Federal law makes it unlawful to use a registered pesticide in a manner inconsistent with its labeling, so a DIY pad made from EZ-OX is an off-label use, and we are not going to tell you otherwise. If you want the extended-release method, buy the registered strip. If you want to use EZ-OX, use it as labeled: vaporize it or dribble it.

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How Much Oxalic Acid to Buy

At the 2 g per brood box we recommend (the label rate is 4 g), a 400 g bag is about 200 single-deep treatments and a 5 lb bucket is over 1,100; at the full label rate, halve those. Some real numbers:

• Five double-deep hives, one summer series of seven rounds plus fall and late-winter broodless treatments: about 160 g a year. One bag lasts two seasons.
• Twenty hives on the same program: about 640 g a year. Two bags, or a bucket that also covers next year.
• A hundred hives: a seven-round summer series at 2 g is 1,400 g on its own. One 5 lb bucket covers the series with 800 g to spare for fall and winter, at about $14 in acid instead of $44 for the same treatments with Api-Bioxal.

The Treatment Series Planner does this arithmetic for your hive count and prints the grams and the number of bags. Sealed and dry, oxalic acid dihydrate keeps for years, so buying a season ahead costs nothing. Dosing by box and the schedule by season are in how much oxalic acid per hive.

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Honey Supers, State Registrations and Safety

Honey supers on. The EZ-OX label permits use when honey supers are on the hive, and the 2021 federal tolerance exemption is why. Manufacturers still advise against treating during an active nectar flow. What the label allows and what the residue data says: treating bees with honey supers on.

State registrations. EPA registration is federal; each state registers products separately. EZ-OX is registered in nearly every state, with California the well-known exception. If in doubt, your state department of agriculture publishes a registered-pesticide list.

Safety. Oxalic acid is an acid. Powder in the eyes or a cut is painful; vapor in the lungs is dangerous. For vaporization, a NIOSH-approved respirator with acid-gas cartridges, gloves and eye protection are the minimum, and you stand upwind. For dribble, gloves and eye protection. Never treat inside an enclosed overwintering building. We use the PD-101 full-face respirator.

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Frequently Asked Questions

Is oxalic acid safe for bees?
Used as labeled, yes. Oxalic acid is one of the gentlest varroa treatments on adult bees and brood, and it does not accumulate in wax the way amitraz and thymol do. Overdosing, especially repeated dribbles, does stress colonies, which is why the label sets a maximum of 4 g per deep box for vapor and 50 ml per colony for dribble.

Can I use oxalic acid from the hardware store on my bees?
No. Wood bleach and other industrial oxalic acid are not EPA-registered for hives. Using them is a federal label violation and the EPA has stated it can make your honey legally adulterated. Use EZ-OX or Api-Bioxal.

Do I need a vaporizer to use oxalic acid?
No. The dribble method needs only a scale, a syringe and sugar syrup, and it uses the same EZ-OX powder. Vaporization is faster, works with the hive closed, and works in cold weather, which is why most beekeepers move to it.

Does EZ-OX work in vaporizers other than the InstantVap?
Yes. It is plain oxalic acid dihydrate and works in any vaporizer. The label rate is the same regardless of the tool.

How often can I treat with oxalic acid?
The label doesn't set an annual limit. In practice: one treatment when broodless, or a series spaced 3 to 5 days apart across a full brood cycle when brood is present, guided by mite washes before and after. Our schedule by season is in how much oxalic acid per hive.

Is EZ-OX the same as Api-Bioxal?
Both are EPA-registered 97% oxalic acid dihydrate. Api-Bioxal's formulation includes glucose and silica excipients that are widely reported to leave a caramelized residue in vaporizer chambers; EZ-OX has no fillers and burns clean. EZ-OX is made in Ohio; Api-Bioxal is made in Italy. EZ-OX costs about 12 cents a dose; Api-Bioxal about 31.

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Sources

• US EPA, EZ-OX pesticide product label, Mike's Bees LLC, EPA Reg. No. 101743-2, amended January 2026
• US EPA, VarroxSan pesticide product label, EPA Reg. No. 94413-3, August 2024
• US EPA, Advisory on pesticides used to control varroa mites in beehives, February 2024
• USDA-ARS Bee Research Laboratory, Oxalic Acid FAQs
• Federal Register, Oxalic Acid; Exemption from the Requirement of a Tolerance, February 2021
• Scientific Beekeeping, Extended-release oxalic acid for varroa management
• WSU Extension, Oxalic Acid Options for Controlling Varroa destructor

General beekeeping information, not a substitute for the product label. Always read and follow the label of any product you use in a hive.