Here is the oxalic acid varroa mite treatment I use on our honeybees. I've used a few mite treatments in the past, tried the varroa resistant queens, one year I did the hands off method, and the oxalic acid mite treatment is the best thing I've used so far. This is based on my use, and other beekeepers I know. Some mite treatments are pretty awful in the hive, oxalic acid strikes a good balance.
Oxalic acid occurs naturally. It is present in spinach and rhubarb, and is found in small amounts in honey. My treatment method is based on a post by Rusty on my fav beekeeping blog, Honey Bee Suite.
One of the great things about this method is that it is super easy. Some people will vaporize oxalic acid in their hives, but this requires some gear, and I don't recommend it for the hobbyist beekeeper. Our treatment process uses a 60 ml syringe. You can buy these at agricultural supply stores, or online here.
This sugar - acid mix is also great for spraying bee packages before putting then in a hive. It knocks down the mite load quite a bit. All the packages I hive are sprayed with it before dropping into a hive. When treating a regular hive, it is best to apply the mite treatment in late fall, when there is little brood in the hive. The acid will not kill any mites that are in capped cells.
The oxalic acid varroa mite treatment recipe:
Oxalic acid is also known as wood bleach. It is used by wood finishers. You may be able to find it in a hardware store. I couldn't find it, so I bought it online, order oxalic acid here. You can buy the syringe here.
Put 600 ml of hot water in a quart Pyrex container, or similar glass jar.
Add 35 grams of the oxalic acid crystals and stir to dissolve in the hot water
Add 600 grams of granulated sugar.
Store in a glass jar - I use a canning jar.
Take the cover off the hive, do not break apart the hive. You apply the acid through the top super.
Measure 50 ml into the syringe, and dribble 5 ml into the spaces between each frame of a 10 frame hive. Some people will use more of the acid in the frame space areas that have more bees in them.
Rusty suggest practicing the dribble with water before doing this, and I agree. It takes a little work to get it right. Rusty references the Scientific Beekeeping site in her post for the exact oxalic acid varroa mite treatment recipe.