> Dr. Krieger mentioned three miticides under
> investigation: flumethrin, coumaphos and amitraz 
> (each with a different gate color) and that a yearly 
> rotation should be used.

> Does anybody have experience in such a rotation program. Does
> it prevent/slow down the build up of the resistant mite population ?

The rotation of those specific miticides has not proven to be a good idea,
in retrospect.

The article below is a good overview - recall that all the miticides listed
for use in "Varroa Gate" are hydrophobic, and will be readily absorbed by
wax, thus exposing the bees to the same sort of conditions that proved what
a terrible idea it was to rotate between Apistan and Check-Mite in their
strip forms.

http://www.beeccdcap.uga.edu/documents/CAPArticle2.html

I believe that flumethrin is very similar chemically to fluvalinate
(Apistan), and Coumaphos is Check-Mite, and amitraz was, until 2012 (Lord,
protect us from the 95% of beekeepers who make the rest of us look so bad!)
a freakin' Cow Ear Tag ("Taktic") massively misused since the early 2000s in
beehives on the east-coast pollination circuit.

We ended up with lots of multiple-miticide resistant mites in different
scenarios, most of the fingers pointing to misuse being the proximate cause
of the quickly-appearing resistance to multiple miticides:

http://www.apidologie.org/articles/apido/pdf/2004/01/M4104.pdf

http://www.apidologie.org/articles/apido/pdf/2000/03/m0312.pdf

Contrast this with the lack of multiple-miticide resistance where only the
pyrethroids Apistan (fluvalinate) and Bayvarol (flumethrin) were used:

"This level of resistance is far lower than that detected following
widespread colony collapse in Italy and highlights the importance of the
correct use of varroacides and of early detection of resistance to enable
its control."

www.bulletinofinsectology.org/.../vol56-2003-175-181thompson.pdf




Note on Chemistry, Wax, and Miticides/Pesticides:
===========================================

It's pretty simple - "Water and Oil Don't Mix."
Substances are either "water-based" (Hydrophilic) or "oil-based"
(Hydrophobic) substance, miticides and pesticides included. 

A hydrophobic molecule is "non-polar". There is no partial negative or
positive charge anywhere on the molecule. So, the molecule repels water.
Hydrophilic (charged and polar) molecules  have a partial charge, allowing
them to hydrogen bond with water, as oxygen is electronegative and that end
of the water molecule is negatively charged.

Hydrophobic pesticides are becoming more common.  This means that more
traces of more and more pesticide and miticides will build up in the brood
combs.  Wax is a sponge.  Ask Jerry B, who can tell you if your bee truck
runs on gas or diesel with nothing but a brood comb sample.  Ask MaryAnn
Fraizer, who has published multiple articles on this specific subject.

This is yet another reason why, despite of Allen and Randy's
recently-expressed love of old black brood combs, I still rotate my brood
combs on a strict 2 combs per year basis, even though I use only organic
acids to control varroa.  I don't know what the bees might bring home, but I
took enough chemistry to know that "wax is a chemical sponge".


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