In our examining samples for a neighbour, we came across one that had the
most varroa we have seen in a sample this spring.  There were seventeen
varroa mites in one sample of roughly 300 bees -- 5.35%, as it works out
using the actual numbers -- in the alcohol wash.  The yard had been treated
with Apistan a year ago.  Yards treated identically (AFAIK) in our own
outfit are returning zero varroa in all the washes we have done so far.

We are recommending that he sample that yard again for varroa, add two
strips of Apistan® and do an alcohol wash again in three or four days.  If
Apistan is still working, then there should be few, if any phoretic mites
after the first two days according to my understanding, since Apistan should
knock down virtually all the phoretic mites within a few days -- if they are
susceptible.

A friend sent me the latest info on testing for resistance, and it involves
exposing a caged sample of bees from a hive with significant phoretic varroa
to a predetermined dose of fluvalinate and monitoring the mite fall and
detecting any mites not killed by the Apistan.

I'm wondering if what we are doing is a good enough quick-and-dirty field
test to assure ourselves that the beekeeper in question is still getting
adequate response to Apistan -- without going to all the bother of the more
elaborate test until later?

What have others found?

allen
http://www.internode.net/HoneyBee/Diary/