We have oxalic, formic and now acetic acid as varroa treatments. Along with
FGMO, all seem to work best sprayed on the bees. All are organic. Is there
a common thread here?

FGMO is supposed to work by suffocating the mites, but that was only a
supposition based of what is supposed to happen using FGMO on horses to
control mites. I have no idea what the mechanism is with the acids, but my
guess is the vapor is what does the killing. Have there been any studies?

It is also interesting that oxalic and formic acids are diluted
substantially to be effective on the mites and not kill bees.

I have no idea what the relative volatility is with each of the acids in
their diluted form, but my guess is they are similar at their effective
concentrations, so there seems to be no reason why vinegar would not work
as well as the others.

If we do not need contact, but only need the vapor, why not use paper
towels soaked in the proper dilution of vinegar in a veggie baggie- one
with holes? Or is vinegar already too diluted for it to work other than
direct contact? If so, then maybe just vinegar soaked towels would do.

Just some musing, but for fun, I put an oil and vinegar soaked paper towel
on one of my hives.
And, I know, if I just add some greens I will have a nice tossed salad.

Bill Truesdell
Bath, ME