Several of our club members are using only essential oils for disease control with success. Some are using HBH and some are using winter green. Mite counts are low and overwinter rates are high and no funny honey. Some are feeding oils in syrup and some are going for contact applications.
I would be hesitant to conclude that essential oils do not work. For example look to all of the various formulations of thymol registered and on the market now. As with any treatment timing and technique are very important to maximize benefit and minimize risk. Our VP and retired chemistry professor recommends these two cites to learn more:
Post by feralfarmer on Feb 9, 2009 14:42:44 GMT -7
I had good success with mite drops after using red thyme oil that i bought at New Seasons. I diluted 10-15 drops of this oil in a pint mason jar of food grade mineral oil and soaked non-bleached paper towels in the mixture. The paper towels were then wrung out well and placed in a loose "S" shape on the top bars of both deeps in each hive. I introduced this method of mite control simultaneously while dusting with powdered divert sugar, so it proved to be an effective 1-2 punch. Unfortunately I was not able to overwinter these hives, due largely I think in part to the colder than usual temps that likely had the colonies eating up their honey stores faster than I anticipated before getting feed to them. I blew it.
I believe it is more or less accepted that the powdered sugar treatments work, ie will cause mites to drop. It would only be useful, for the purposes of this thread, if feralfarmer left the powdered sugar treatments OFF and only tried the essential oil treatment, with mite counts before and after the application. Then we can say whether or not essential oil causes mite drop.