I have to agree with Dan about the number of yearly Apistan treatments but
not for the same climate reasons as his.  I keep  my bees in Northern
Maryland, treat  at end of February, mid to end of July after supers come off
and in the first week of October.  Maryland beekeepers lost up to 70% of
their bees last year while I was fortunate to have not lost any out of 10
hives and was ables to get 9 Nucs with 4 frames of brood per Nuc.  Even in
the little state of Maryland we have up to a two week difference when the
honey flow hits from down south to where I live on the Pennnsylvania border.
 I don't know if it was the fact of the 3 applications or the timing of the
applications.  I also treat with grease patties at the same time with the
February and October patties containing TM.
Mike