Observations
- at low temperature, the thymol does not release in sufficient concentration and thus is not effective. Few 2 zero mite load reduced
- at warm temperature the thymol releases to fumigate the hive and becomes effective. Too warm and it releases in higher concentration which actually chase the bees out of the hive. The bees do not like it, they barely tolerate it. I have not noticed signs of the thymol to kill or damage the bees. I have seen nearly the entire colony rush out of the hive and hang on the outside of the boxes within a day after first application. I can imagine if the conditions inside persisted, they would leave (abscond), though that did not happen with mine.
Look at your normal seasonal ambient conditions and the 2 week weather forecast for your area. If temperatures will be within the target window, the thymol will work. Just know up front that it will not cause a huge drop or eradication of mites in the hive like the other treatments, however under the right conditions the thymol will definitely cut the numbers back quite a bit. It is expensive compared to the others, $/hive, and is not nearly as effective. That said it does work, somewhat. If thymol is all you have, it is much better than wasting time sugar dusting and significantly better than nothing.
Hope that helps!