You don't have to treat colonies for tracheal mite in the spring because the
queen bee
can lay enough brood that tracheal mite damage is not a problem.

Almost all bees that die of tracheal mite die in late December or January
because the
queen has NOT layed any new brood back in late October or November, and hence
all
these "old" bees are sick with tracheal mites.

Menthol KILLS tracheal mites extremely well IF IT IS INSTALLED IN VERY WARM
WEATHER which for Maine would probably be August 1st.  September would
definitely not be warm enough and menthol would not sublime into a gas that
kills the mites.

Dr. Diana Sammataro's research with GREASE PATTIES earned her a Ph.D., but it
labor intensive but works.  You mix 2 pounds of plain sugar with 1 pound of
Crisco, and make patties about the size of a hamburger.  Put one pattie on
top of the frames of the bottom brood chamber no later than July 1st, and it
MUST BE REPLACED as soon as the bees use it up.  Hence it MUST be
continuously used for about 5-6 months, from July to December.  DO NOT USE
ANY TERRAMYCIN EXTENDER PATTIES.  This treatment does NOT kill tracheal
mites, but controls their population so that they do not harm the bees.

I hope I have helped.

George Imirie
Beginning my 70th year of beekeeping in Maryland
Certified EAS Master Beekeeper
Author of George's PINK PAGES