Important Safety Notice

Unless you have, and are committed to always wearing, the required personal safety equipment, including a half-face respirator with acid gas cartridges, DO NOT ATTEMPT to use this method.

Oxalic acid “vaporization” is somewhat of a misnomer, because the principal chemical change is actually sublimation, not vaporization. The oxalic acid is heated until it sublimates, i.e. turns directly from its solid form (white crystalline powder) into a gas without passing through a liquid stage.

Above the sublimation temperature of oxalic acid (314 degrees F) the remaining minor components of the material are only briefly in a vapor, before everything cools back down. As it cools back down, the oxalic acid forms a visible cloud of very tiny, spikey, crystalline, acid dust particles that are deposited all over the interior surfaces in the hive. (Or the insides of your respiratory tract if you aren’t wearing your properly-fitted mask, as required.)

Keep in mind that oxalic acid vaporizations can be done with wooden equipment, or with BeeMax and Lyson polystyrene hives. However, the hot parts of the vaporizer that vaporize the OA can easily melt the polystyrene of the hives, and so care must be taken when using this method with non-wooden equipment.

Oxalic acid vaporization during the broodless period can be done in outside air temperatures as low as 37 degrees F, but a better range is in the mid-40s to low50s F.  At these temperatures the bees will be clustered in the hive and stay during the process. 

Start out by planning on doing a single hive from start to finish. As you get more experience, you will see that you can speed up the process by having two hives cycling though the process simultaneously: one hive started and carried through to the sealed-in stage after the wand has been withdrawn. Then, during the sealed-in stage on the first hive, another one is started with the freshly-filled wand, and so on. Treating a second hive concurrently requires an additional timer to keep the different cycles straight. However, since safety for both you and your bees should be your primary goal, start off slow and work your way up to doing more than one hive at a time.

Please read and follow all the instructions that come with the Varrox wand.

Steps for how to do oxalic acid vaporization

If you have a screened bottom board, clean off and prep the sticky board before beginning the treatment. Expect to see the biggest flush of dead mites in 24-36 hours after treatment.

Follow these steps to safely and effectively perform oxalic acid vaporization:

  1. Close up (plug or tape over) any upper entrance. Then remove the entrance reducer and give the bees a puff of smoke to loosen the cluster and get them fanning.
  2. Bend down and use a flashlight to see if there is any comb hanging down from the frames into the center of the hive where the wand will go.
  3. Move the battery close to the hive and connect one terminal (use either one, there is no polarity between the leads).
  4. Set a timer for 2 minutes and 30 seconds. This is the length of the active burn stage.
  5. At this point, put on your mask and do an inhale/exhale fit check. Your wand will come with specific instructions on how to do this check. This crucial step should be done every time you put on the mask, even if it’s only been off for a few seconds. It’s a test to make sure the mask is properly seated on your face to give you full protection.
  6. Put on your goggles and gloves.
  7. Count the number of boxes on the hive, as this determines the amount of oxalic acid to use. The dose is 1/4 teaspoon per box, of any size. Except for nucs, which get a half-dose, i.e. only 1/8th teaspoon per box.
  8. Use the dip-and-sweep method of filling the measuring spoon, using the back of a plastic knife to level off the powder. Don’t pack it down in the spoon, just sweep the excess off with the knife. Dump the powder into the cup of the wand.
  9. Give the bees another puff of smoke to maintain the loose cluster and push any curious ones up and away from the entrance.
  10.  Slide the wand into the middle of the hive until you reach the dark colored section of the wand’s stem. This positions the wand correctly from front to back. If there was any comb hanging down from the frame, move the wand over to the side to avoid getting the hot pan close to it.
  11.  Seal up the front entrance around the stem of the wand using paper towels. Make sure the wand remains level and flat on the floor of the hive.
  12. Timing Sequence for the Varrox Wand

    Active-burn stage 2 minutes 30 seconds
    Power-off stage 2 minutes
    Sealed-in stage 10 minutes
    Immediately after sealing, connect the second lead to the battery and start the timer to begin the active burn stage. Watch for leaks, and if they are significant you can seal them up with tape. After about a minute you may hear the bees fanning forcefully and begin to see small wisps of smoke emerging from crevices. This is normal and it does not mean the bees are in danger. When the timer sounds at the end of the stage, just disconnect one lead from the battery to cut the power.
  13.  Leave the wand inside the hive and start timing again, this time for 2 minutes, this is the power-off stage.During this time, set up your bucket of water for dunking and cooling the hot wand after it is withdrawn from the hive.
  14.  When the two-minute, power-off stage is done, remove the hot wand from the hive, and immediately reseal the entrance with the paper towels.
  15.  Start a timer set for 10 minutes, which is the sealed-in stage.
  16.  Dunk the business end of the wand in the water to cool and clean it. It will likely hiss a bit, and this is OK. Afterwards, wipe it dry to get it ready to start another treatment.
  17.  When the 10-minute sealed-in stage is finished, remove the paper towels and unblock the upper entrances and let the hive ventilate for 10-15 minutes. Then close it back up as it was before you started. This completes the treatment for the hive and it is safe to remove your mask at this point, unless you have another hive cycling through the process.

In cool weather the bees are unlikely to come out of the hive in any numbers when it is reopened after treatment is completed. In warmer weather they sometimes do. This is perfectly normal and doesn’t mean there was a problem. They will settle down quickly.

Very occasionally you will find an unlucky dead bee in the pan when you withdraw the wand. Next time make sure the wand is wedged flat and use more smoke to shift the bees upward before starting the burn.

Getting started with oxalic acid vaporization

With all the emphasis on wearing a respirator, and talk of sticking a 300+ degree F wand into your hive to create clouds of tiny acid crystals, you may feel a bit anxious about using this method on your bees. Don’t let that deter you from trying vaporization. Unlike humans, the bees easily withstand exposure to the treatment. The bees will be fine and receive the enormous benefit of removing more than 95% of all varroa mites in the hive from just one treatment. Oxalic acid vaporization has been used for decades in Europe and has a proven record for bee safety and efficacy.