In response to the message of Ted Fischer:
 
It is not necessarily true that a 0.02% mite infestation level after a
spring treatment will grow to a treatable level by the late summer or
fall of the same year. It is essential, though, that all colonies in an
apiary (and even neighbouring apiaries) be treated at the same time. Mite
increase due to immigration is often greater than the intrinsic rate of
increase within a hive.
 
Regarding resistance to fluvalinate: it is also not necessarily true that
those mites not killed by a treatment are resistant to the chemical.
Furthermore, overapplication and "insurance" treatments will only hasten
the process of resistance buildup. It is undoubtedly misuse of the product
which has created the problems now being encountered in Europe.
 
Just my two cents.
 
Paul Gatien