if you fork and you see a few in the drone...you have a problem. Number of drones is realitive to the number of mites. However Medhat Nashir (bee guru) has a saying...if you see seven, you have a problem...big problem

Randy Oliver says this....

"There is a strong trend among recreational and sideline beekeepers away from synthetic miticides, motivated largely by the desire to engage in "chemical free" beekeeping. However, you can not truly call yourself a "beekeeper" if your bees keep dying on you!" There is a bigh difference between natural beekeeping and simple colony neglect. I suggest that all beekeepers familiarize themselves with the pros and cons of the available miticides, should the nees arise to save a colony from an ugly death. You can visit Scientific Beekeeping.com for my in-depth articles on mite management and details on miticides."

ABJ Feb 2011 page 145

Randy Oliver walks the walk on giving up synthetic miticides over 10 years ago. But to keep the mites in check he still uses some sort of treatement as needed. In his article he does not condon the use of synthetics however he says use it wisely.
Here is a copy of the article. It is a good read. Will give you alot of help and information in choosing a method of treatment
I like formic my self