> Quote- with some editing: get a  100 gram bottle of thymol.  Add 1/2 ounce
> of menthol and 1/2 ounce of champhor.
> Fill the bottle with Eucaliptus oil.  Let it stand for a day in the sun
> until all is disolved.  buy a pack or two of cheap (10 for a buck).....

I see several problems with the homemade formulation of thymol in this post.  Thymol, like many other natural product acaricides, is not tremendously selective, that is to say that the dose which kills bees is not much higher than the dose which kills bees.  Laboratory studies performed in Canada indicate that thymol and formic acid are only 5-10 times more toxic to mites than bees- compared to fluvalinate which is thousands of times more toxic to mites.

TAKE HOME MESSAGE- Before I would use any thymol formulation I would: 1) make sure it is registered for use in my area and 2) make sure the formulation has been evaluated in multiple scientific studies.  Guessing that a soaking sponges in a thymol/essential oil blend 'sort of kind of sounds similar to a method used by a researcher' is not good enough- the amount evaporating into the colony may not be comparable- and because of the low selectivity- being off can mean the difference between adequate mite control and bee death.

> This treatment was developed by Nick Calderone sp? when he worked at
> Beltsville.  According to his talk on the subject he had somewhere around
> 99% kill rate.  The actual formulation of his was 75% Thymol, 16%
> Eucaliptus, 4.5% Campher, and 4.5% Menthol.

Thymol-based treatments, like formic acid, provide variable, and often marginal control.  The post cites work by Dr. Calderone that resulted >95% varroa control.  Further studies by Dr. Calderone with thymol formulations have yielded < 70% control.  The reasons for the variability are likely many, but do not seem to be easily dealt with.  Thymol is not a cure all, but it will likely will play a role in a integrated strategy.

Regards
Adony