Something has gone a little bit array here. I feel that if one wants to use powdered sugar treatments, go for it, if one wants to use formic or oxalic acid, go for it, if you want to use other chemicals go for it. Do what you feel works.
I do not believe that any chemicals such as coumophus (spelling) or fluvalinate should ever be used in the colonies, and there are a couple more, if I am not mistaken. There can be long-term residue left in the colony and can also be found in wax and honey. These type of chemicals are not to be used 45 days before the anticipated honeyflow. Now that says something in itself, right there. These, in my eyes, are the "bad chemicals".
I only have to "bother" my colonies twice per year, if needed, once in the fall and once in the spring, and that is not with oxalic acid trickling, which can kill brood if it is present, but using the vapourizing method of the oxalic acid crystals, which can be done when brood is present, and DOES NOT kill brood. Oxalic acid sugar syrup trickling can be very effective too. I also stand behind the use of formic acid treatments within the colony. I also have a little faith in the small cell factor, which evidently can be good for mite control, but that is not for me either.
Whatever methods you believe are good, go for it. Powdered sugar treatments is far too time consuming for me to bother with. I think the time frame is treating very frequently, and I just could not be bothered. And yes, Rob was correct, I am an advocate for oxalic and formic acid treatments. If there are high mite counts, something must be done, whatever you feel you have to do, otherwise face colony collapse, period....no ifs, ands or butts, the colony will collapse, if not that year, the following year. I have been there with the loss of 10 colonies to mites, never going there again. Just wanted to clear the air a little bit. I feed sugar syrup to my bees, and there is nothing wrong in my eyes, to do that powdered sugar treatments either. My part of this discussion is closed. Have a wonderful and awesome day, Cindi