>But the varroa-gate miticide is Coumaphos (Bayer Check-Mite).   Not sure
that this is a good idea given the widespread resistance to Coumaphos that
appeared back when it was more widely used:
www.apidologie.org/articles/apido/pdf/2004/01/M4104.pdf

> From a recent presentation at University Ghent:


In this presentation, 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.



>And what kind of dose is required to get a reliable contact kill on varroa
so effective that they die before they can mate?


They first tested this in a lab experiment where they allowed the bee to
pass the gate once and measured the time needed for the mite to fall off.
They have done several field studies also looking for the right dimension of
the holes (for best transfer of active, sufficient ventilation, drone
passage).



He presented the product as a tool to prevent horizontal transfer between
hives (trough robbery), next to other measures (biotechnical, acids,
thymol). It understood that the product should be used after the summer
harvest and after the summer treatment (I guess robbery is more frequent
then, especially in 'bee-dense' areas with variability in strength of
hives). It was not clear to me if this was the indication that would be
retained on the leaflet of the product. I can imagine that some beekeepers
would be tempted to use it throughout the year.



> For example Last year I checked for coumaphos efficacy in Alberta Canada,
efficacy was 18-22%. Mites were still resistant as 5 years ago.

Dr Pettis already suggested rotation of miticides in 2004 (see the article
in apidology). Does anybody have experience in such a rotation program. Does
it prevent/slow down the build up of the resistant mite population ?



Kris Baert
Belgium
(in my third beekeeping year)

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