From BetterBee:
Oxalic Acid Dribble is a method that uses oxalic acid mixed with sugar syrup. It is applied using a large syringe to squirt the mixture onto 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 an 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.
Honey Supers: This treatment is most effective in the winter. Do NOT apply to honey supers. Only apply to brood boxes.
Temperature Range: none
Usage
* BetterBee Instructions
* Honey Bee Suite
* Randy Oliver – Oxalic Acid Treatment Table