Oxalic Acid Dribble is a method which uses oxalic acid mixed with sugar syrup. It is applied using a large syringe to squirt the mixture on to the bees clustered between the frames.
The bees are not harmed by physical contact with the oxalic acid-laced syrup but, inevitably, they consume a small amount of the oxalic acid containing-syrup which is mildly harmful. For this reason, oxalic acid dribble is best done in a single treatment, not in a repeated series. This is particularly important in winter when individual bees must stay alive for a much longer time. Fortunately, during the brood pause, a single treatment is usually all that’s needed, so oxalic acid dribble is a satisfactory option at this time of year. The method works best when there are only two boxes on the hive. It can be used when there are more boxes (such as in a hive made up of three or more medium boxes) but that makes for extra work.
The equipment needed for mixing and applying the treatment is modest and inexpensive: a gram scale, glass containers to mix the oxalic acid and sugar syrup, a plastic or wood stirrer, and a 60 cc plastic syringe to do the dribbling in controlled and measured amounts. You can assemble the mixing items on your own from household items and add our oxalic acid dribble kit which comes with everything else you need: the oxalic acid, the syringe and the personal protective gear.
The required personal protective gear includes a particulate (N-95) mask, eye protection to protect your eyes from any splashes while mixing and applying the solution and gloves to protect your skin from the acid.
You will need an accurate way to measure the oxalic acid, a scale that reads in grams is the best choice. Use mask, gloves and goggles when mixing. See the table at right for mixing recipes. Mix the correct amount of oxalic acid with the appropriate amount of hot water. Stir the mixture until the crystals of the oxalic acid are dissolved. Do not shake the container. Stir in the sugar until it is dissolved. Close the container tightly and add a label: POISON 2.5% Oxalic Acid. Never place the mixed syrup in repurposed food containers, especially drink bottles where it might be mistaken for a beverage. Do not keep any unused syrup after treating; dispose of it by diluting with a large volume of water and pouring down the drain.
When working with oxalic acid in syrup, always have a source of clean water available to use to flush any accidental contact with skin or eyes.Take a couple of gallons of fresh water to the bee yard with you when you go out to do the treatment.
Always wear your safety equipment (mask, eye protection, and gloves) when working with the mixture.
Winter oxalic acid dribbles can be done in temperatures as low as the low 40s, when the bees will likely remain clustered during the few minutes the hive is open. While oxalic acid dribbling can successfully be done by one person alone, it will go more quickly if you have a helper. One person can then do the box-opening part and the other person can do the actual dribbling. The helper, if you have one, should also be wearing a mask, eye protection, and gloves.
To begin, draw 50 cc (this is the maximum that can be used in a single colony) into your syringe and set it aside.
Remove the telescoping cover, but not the inner cover. Then use your hive tool to break the propolis seals between the boxes. If you have more than two boxes in your stack be prepared with a temporary base on which to set the upper boxes while you work on the lower ones.
Tilt up the top box and look underneath it to see if there are bees in it. (See the box below for how to safely tilt up a box.) If you have more than two boxes on the hive, move the tipped-up box to the temporary stack, cover it, and continue to work your way downward. Repeat until you have tilted up the next-to-lowest box. When you have the bees in the lowest box exposed, you’re ready to begin the treatment. No need to remove the next-to-lowest box, just keep it tilted up while you treat the box below.
Once you’ve exposed the lowest box where the bees are visible, use the syringe to trickle 5 cc of the oxalic acid/sugar syrup mixture over the bees in each of the seams (spaces) between the frames. Do not apply the mixture to any empty seams where there are only a few, or no, bees. Try to get exactly the right amount per seam. When you’ve done the first box, set the tilted box back down and do the same thing to it if there are bees in it: apply 5 cc of the mixture on any seam where the bees are visible. Repeat, as needed, with any additional boxes that have bees. Do not exceed a total of 50 cc per hive. Then replace any remaining boxes from the temporary stack and close the hive back up.
If you have a screened bottom board on the hive and can monitor mite drop on a sticky board, expect to see the largest drop beginning in about 24 hours from the treatment. You may be startled (and maybe gratified) to see how many mites were removed from your wintering colony as a result of treatment. Those are mites that would have jump-started an early mite build-up in the spring.