Tom,
Just a few days ago it was said that in Ireland they didn't want to know
about any treatment that didn't involve Bayvarol - how very foolish.
Relying on a single product to solve the problem is asking for
trouble.......
Resistance to fluvalinate also means resitance to flumethrin and amitraz,
however as coumaphos is in another class of chemicals it is very effective
where fluvalinate resistance is present.  I think that it is very important
to rotate treatments from the beginning. As wide a variety as possible
should be used.  This is done in some countries, with a general agreement
being reached by the beekeeping associations as to which treatment should be
used each year. This of course delays the build-up of resistance to any of
the products and hopefully will buy enough time for research by bee
scientists to come up with something that will control the mite forever.
For example small cell foundation or one of the fungi presently being
tested.  Just as a matter of interest, we have had Varroa since 1982!
Best regards
Roger White
Superbee Cyprus.