Not only Dr. Rinkevich, but also, Pettis, the Canadians and Sagili have
tested in North America (these are only individuals or groups that I know
of or have discussed with).

Be aware that the term "resistance" means different things to different
people.  Some define it as the inability to achieve 90% kill , whereas
others are tracking the increase in the LD50 or LD90 (the interpretation
that I'm interested in).

It's always been disingenuous to claim that amitraz doesn't contaminate
honey or combs, since it immediately breaks down into 2,4-DMPF or other
metabolites, which are readily absorbed by beeswax, and show up in honey.
It's not clear whether these metabolites have miticidal action.

Resistance comes from repeated selection against non-resistant stock, not
so much by how it is applied (and amitraz has been applied in every
conceivable way -- some quite dangerous to the applicator).

Unlike as with fluvalinate or coumaphos, there appears to be a substantial
"fitness cost" to gaining resistance -- otherwise the resistant mites would
be easily outcompeting the susceptible ones.

The take-home message is to ROTATE TREATMENTS. And use treatments that
don't leave persistent residues in the combs.

Randy Oliver
Grass Valley, CA
530 277 4450
ScientificBeekeeping.com

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