Knowledgebase is a categorized collection of answers to frequently asked questions (FAQ) and articles. You can read articles in this category or select a subcategory that you are interested in.
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 the oxalic acid vaporizations should only be done with wooden equipment, not with BeeMax or Lyson polystyrene hives.
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though the process simultaneously: one hive started and carried through to the sealed-in stage after the wand has been withdrawn.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.
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:
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.
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.