Oxalic Acid Fogger Demostration

Snapshot 2 (2-3-2014 9-54 AM)

When it comes to Varroa control, beekeepers have always been concerned about mites’ resistance to commercial treatments available on the market. It seems the arms race never ends, but changing up treatments throughout the year can help ensure that resistant mites don’t get a foothold. There is a lot of interest in alternative mite control methods, and one that may be a useful addition to the beekeeper’s toolbox is oxalic acid.

Oxalic acid is an organic, naturally occurring compound which can be found in high concentrations in certain plants, notably spinach, rhubarb, and and the aptly named Oxalis. These plants use it as a deterrent against herbivores by making tissues sour and unpalatable (try munching on a raw rhubarb stalk for a demonstration). Oxalic acid is approved for use by beekeepers in Europe, but is still not approved in the U.S. The advantages of using oxalic acid for mite control are as follows: it’s naturally occurring and organic, relatively easy to apply, and is not fat-soluble and therefore does not build up in the wax. The most common method of applying oxalic acid is mixing it with syrup and using a “dribble” technique in the fall or early spring. Mites in sealed brood are not affected, therefore oxalic is not usually used in summer or when there is a significant amount of brood present.

Recently the NorCal Bee Team had the opportunity to assist with a trial of an experimental oxalic acid vaporizer here in NorCal. Oxalic acid clogs normal off-the-shelf foggers, but a local beekeeper/inventor designed a special vaporizer that supposedly does not clog and can save beekeepers time and money when treating for mites. We were called in to assist with the trial by looking at mite levels before and after the fogger was used. The supposed benefits of fogging over dribbling are less ingestion by bees, quicker time to treat (less than 1 minute per hive), and even distribution of acid crystals throughout interior surfaces of the hive. The video below gives an idea of how the fogger is used.

Unfortunately we cannot say if this vaporizer is effective or not because it turned out that there were very few mites to begin with. Another demonstration is being planned so stay tuned!



Written By: Ben Sallmann

Ben Sallmann has written 12 post in this blog.

As part of the Pacific Northwest Tech Transfer Team, I work closely with beekeepers and breeders in the region and assist with colony assessments, disease monitoring, sampling for pesticides and viruses, and testing breeder colonies for hygienic behavior. My interest in bees began as a child working on our family’s apiary/organic vegetable farm in Wisconsin, and I joined BIP in the summer of 2013 in order to be more involved with hands on research that benefits beekeepers in a tangible way. I began my work with BIP based out of the University of California Cooperative Extension office in Butte County, CA, but in 2017 moved to Oregon to work with the Pacific Northwest team, based out of OSU in Corvallis.


8 Responses to “Oxalic Acid Fogger Demostration”

  1. Charlie parker

    I am doing a project on the decline of bee and i am not sure where to start? I am looking for any graphs showing me the CCD in the last 10 years
    If you could help I would be grateful

  2. Grant Hicks

    Have you looked at the oxalic fogger that Cowan’s built several years ago. It is expensive, but fast. We had two of them and did 1500 hives in 12 hours. It proved that the burners were too hot at that time (at least 5 years ago) and so the treatment was not effective. I have not followed up because they were expensive ( I borrowed the two machines we used) for my taste, especially if they were ineffective. They worked extremely quickly and were easy to use. I would look at them again if they proved to be viable.

  3. George Smith

    I bought a Varroa Smoker Cannon, made in Ukraine, but cannot determine the concentration of oxalic acid with which to load the gun. Any suggestions?