I have been treating hives for Varroa using my own formula made from crystals of Thymol 91% alcohol and high grade mineral oil. 8-12 grams of Thymol crystals dissolved into about 3 ounces of 91% alcohol and then after dissolving the formula I add about 6 ounces of high grade mineral oil. I cut cardboard strips about 8 inches long and 1 -2 inches wide and let these soad for a period of time in the solution. After soaking I place these in a ziploc bag and transport to the bee yard.
My method of placing these in the hive varies, I have placed some of these down in the brood chamber between the frames and others I have placed on top of the brood chamber top bars. My success has been good, I seem to get good results from either application. I have been repeating these applications again in ten days.
Does anyone have other formulas for mixing?
Also I have soaked beer coasters and used on the top bars as well, they work just fine.