Overview

The extended-release application method is not yet approved by the EPA.  Until then, it is not legal to apply OA by this method for mite control, and Gilroy Beekeepers Association does not in any way promote beekeepers doing so.

Randy Oliver:

"Beekeepers worldwide are caught between a mite that has proven able to rapidly develop resistance to synthetic miticides, and the slow pace of development and adoption of mite-resistant bee stock - the eventual solution to varroa.  During the interim, by choice or lack of alternatives, beekeepers are shifting to the use of “natural” treatments.  Oxalic acid (OA) is one of the most promising of those treatments, but its efficacy is limited unless applied during a broodless period. An extended-application method would free it from that limitation.

The problem with oxalic acid is that either of the currently approved application methods (dribble or vaporization) kills mites for only about three days.  So unless applied during a broodless period, or repeated at 4-day intervals, oxalic is not very effective over much of the season, due to a proportion of the mites being protected in the sealed brood.  By creating an extended-release formulation, we may have found a treatment that is “natural,” suitable for organic approval, safe for the applicator, non-contaminating of honey, shows no noticeable adverse effects upon the colony, as well as being inexpensive and highly effective at reducing mite populations."

We will refer Extended-Release Oxalic Acid treatment as OAE.

References

Please read the following references for more details on this treatment technique.

The following links are from Scientific Beekeeping, a website published by Randy Oliver. Randy Oliver is a world-renowned speaker, educator, bee biologist, leading researcher, commercial beekeeper, and regular contributor to the American Beekeeping Journal. He is one of the premier beekeeping speakers in the U.S. and the owner/author of http://scientificbeekeeping.com.

The following is how I (Jamie Haskell), do it. Please do your research and verify your own method.

Shopping List

OAE is a very inexpensive treatment, but you need some gear to safely and accurately make it. Here's what has worked well for me:

Equipment

Item

Name

Description

Purchase
(price as of May 2022)
Induction Cooktop Provides a safe, no-flame way to heat up the solution. The cooktop surface does not get very hot during use, as the heat is induced directly into the pan. One less thing to worry about. Amazon

$62

Digital Kitchen Scale To weigh the Oxalic Acid and Glycerin Amazon

$28

Pan 1/3 6" deep To make a double boiler to heat and mix the OA solution. Amazon

$20

Pan 1/3 4" deep To make a double boiler to heat and mix the OA solution. Amazon

$13

Kitchen Tongs Mixing the solution and bathing the dishcloths. Amazon

$13

Supplies

Item

Name

Description

Purchase
(price as of May 2022)
Oxalic Acid The key ingredient. Handle with care - OA is toxic and very acidic. Always wear gloves, eye protection, and a mask. Amazon

$15

Provides 22 40g doses
Cost per 40g: $.68

Vegetable glycerin Used to dissolve the OA and adhere to the pads.

Best measured by weight. 40g is approximately 33ml.

Amazon

$10

Provides approx. 28 doses
Cost per 40g dose: $.36

Swedish dishcloths. These are soaked in the OAE solution and placed in the hive. Amazon

$20

Provides 10 doses
Cost per dose: $2.00

Startup cost (equipment and one set of supplies): $166
Treatment cost per hive (one saturated Dishcloth, with 40g OA): $3.04

How To Prepare

Recipe

Per hive:

  • 1   Swedish Dishcloth
  • 40g   Glycerin
  • 40g   Oxalic Acid
Note: Randy Oliver's experiments range from 30g to 50g OA per hive. 

Prep

Best do this in a sheltered outdoor area with no wind, or perhaps in the garage. Oxalic Acid is toxic... I would recommend not doing this in the kitchen or indoors. If you are outside, be careful about the OA blowing around. It is a similar consistency to granulated sugar, so a gust of wind would tend to blow it around, making for a hazardous workspace and more involved cleanup.
1. Cut the Swedish Dishcloths in half.
2. Prep your storage container - I use a heavy-duty Ziploc bag, and roll back the top so it stays open for easier insertion of the finished pads.
3. Put on your eye protection, gloves, and mask.
4. Put about an inch of water in the deeper pan, and bring it to a boil.
5. Put the shallower pan on the digital scale, set it grams, and tare it.
6. Slowly pour in the glycerin to the computed weight (40g x number of treatments).
7. Tare the scale.
8. Carefully add the Oxalic Acid to the computed weight (40g x number of treatments).
9. Put the shallow pan in the boiling deep pan. Use the tongs or a spoon to stir the mixture. Stir occasionally and wait until the mixture is clear, and all the OA is dissolved.
10. Turn off the stove.
11. Insert the Swedish Dishcloth halves, and use the tongs to gently move them around until all of the OA mixture has been absorbed by the towels.
12. Place the OA pads into your storage container, seal, and rinse off the outside and your gloves to remove any residual OA.
13. Thoroughly rinse off all your equipment outside.

Usage

Place two half pads (one full Swedish Dishcloth) on the top bars of the lower brood chamber in the spring. They can remain in the hive until the fall.