Soon it will be time for the last mite treatment of the year.
Oxalic Acid is used for this treatment. Oxalic Acid is wood bleach. Oxalic Acid was discovered to have good properties for killing mites it comes in contact with.
Beekeepers use this treatment in late October.
The reasoning is this, in late October most hives have shut down brood rearing and is broodless in the hive or close to it. The Oxalic Acid mite treatment is only effective on mites that are on the bees. These are called Phoretic mites. Phoretic mites ride on adult bees feeding on their blood such as a wood tick on humans. Being there is no brood in the hive, all mites are on the bees. This is a time when these mites are very easy to kill using Oxalic Acid. By treating at the right time, in a broodless colony, Oxalic Acid can kill 90% of the mites that are on the bees. If there is brood in the colony, the Oxalic mite treatment may not be as effective.
A beekeeper needs to pick a time when it is 40 degrees at the time of treatment. It can warm up during the day, but 40 degrees is an important factor, especially for the dribble method. When it is 40 degrees, the bees are in a tight cluster. All the bees are usually present in the box under the top box on a hive. This concentration of bees makes the dribble method work the best.
There is two treatment options. The Dribble method or the Vaporizer method.
The dribble method takes a solution of Oxalic Acid and sugar water in a syringe and squirting the solution on the bees.
The Vaporizer method takes Oxalic Acid powder on a vaporizer pan, plugging it on to a 12v battery and vaporizing the powder which floods the colony with Oxalic Acid vapor. This vapor coats the bees and the inside of the hive with Oxalic Acid.
Both of these methods work. The vaporizer method may work a little better, but either way works.
Oxalic Acid Link: EPA Label with safety and directions for use
Here are two videos on the Dribble and Vaporizer Oxalic Acid Application: