We live in Northern Alberta (Peace River area) and we are (almost) unable to
leave Apistan in the fall in our hives for six weeks. In the fall of 2001 we
treated one yard with relatively high mite counts after removing the last
honeysupers and we were wrapping five weeks later. We don't like to
leave those strips in over winter,  trying to avoid resistant mites building
up faster yet.. When we removed the strips, most of the colonies already
clustered. We have a very short, intensive season here and in the spring we
have just about six weeks after unwrapping to use Apistan and putting up our
first honey supers.I cannot see us waiting for a chinook day, unwrapping our
hives and taking the strips out. There even may not be a chinook that
winter.
 We treated another yard with three single applications of  formic acid (4
days interval) and we didn't see much wax nor propolis buildup on those mite
wipes, even though we were feeding. We used formic for tracheal mite
infestation and hope it sets back varroa at least a little bit.
.
Maria van den Berg.