Applying oxalic acid in vapour form. I use a Heilyser Technologies vapourizer attached to a 12-volt car battery. Acid is in the bottle on top of the hive, purchased from a chemist. (Photo: Amanda Goodman Lee)

Treating bees with oxalic acid; a late-winter mite-killing exercise

It’s the beginning of February and we’re just starting to get busy for the start of the new season.

If you are like me, you will have a long list of unfinished chores from the fall. From cleaning up and repairing boxes and equipment to finishing those ambitious workshop projects that are supposed to make our lives easier, the list is endless.

We’re also a little late – but not too late – on a really important job, reducing the overwintering mite load down to its lowest possible numbers. After the fall mite treatments with formic acid, we wait until brood-rearing is at its lowest point in the winter, and then apply oxalic acid in vapour form.

You might think that late January and early February is too late, but it actually is the optimal time, just before the queen begins laying again in any significant amount.

The job is to catch the mites that are phoretically living in the hives, attached to bees rather than hiding with brood. This is the time when a proper application of oxalic acid will knock many of them off, giving your hives a helpful boost as they go into spring with the lowest possible levels. Oxalic acid does not penetrate capped cells, so any mites in there are still a problem. Hence the idea of doing it when capped brood is at its lowest.

We use a vaporizer made by a Vancouver Island company, Heilyser Technology Ltd. It includes a pan that, when connected to a 12-volt car battery, heats the acid and creates a smoke. The device does not come with the switch and necessary connections to the battery, but that is very easy to make. Doug Brown from West Vancouver produced a helpful video a while ago that guides you through the process. I made my power cord in a matter of minutes. Here’s a video Brown did a while ago.

The value of treating with oxalic acid cannot be underestimated. Randy Oliver, Mr. Scientific Beekeeping, dealt with this treatment in two articles. The first is on the drip or dribble method (which can be used when weather allows hives to be opened), and the second is on vapourization a preferred northern method. In his second article he pays homage to Medhat Nasr, the Alberta provincial apiculturalist who is a subject matter expert on this acid.

Vapourizer, without battery attachment, made by Heilyser Technologies of British Columbia (Photo courtesy of Bedillion Farms)

Vapourizer, without battery attachment, made by Heilyser Technologies of British Columbia (Photo courtesy of Bedillion Farms)

You pre-load the vaporizer with about two grams of oxalic acid crystals, insert it into the hive entrance and turn it on. We place a towel at the front to close it off and prevent bees from escaping.

After a minute or so the  the vaporizer can be turned off and removed, leaving the towel in place a little longer.

Use a facepiece or faceplate respirator, gloves and mask.

Use a facepiece or faceplate respirator, gloves and mask.

A word of caution: don’t do any of this without the proper personal protection. I use an air-purifying faceplate respirator equipped with carbon cartridge filters, as well as enclosed eye protection. I also use industrial rubber gloves. It is not worth frying your lungs, or burning your eyes or skin. A little bit of protection goes a long way.

This, by the way, is the same rule you should apply to any treatments you apply to your hives, whether they be “natural” such as formic and oxalic acids, or synthetic miticides.

Last week we applied oxalic acid to about two-thirds of the apiary before we ran out of time. It’s a bit of a tedious chore, and while I was doing it Amanda was goofing off with the dogs. I turned around and discovered Steinbeck is our newest beekeeper.  However, without opposable thumbs to hold the hive tool, he’s just all paws.

Steinbeck the bee dog. (Photo: Amanda Goodman Lee)

Steinbeck the bee dog. (Photo: Amanda Goodman Lee)

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One Response to Treating bees with oxalic acid; a late-winter mite-killing exercise

  1. Doug Brown March 16, 2015 at 10:27 pm #

    I was reading the article just now and was pleasantly surprised to see myself referenced :) I’m still amazed at how popular that video is, and I’m glad you got use out of it.