The reason I am looking at the persistence of OA crystals is because the
mites are not always on the bees. When they come out of the cells they can
either be on the emerging bee- so the OA would not get them post treatment,
or crawl out of the cell looking for a bee and the OA crystals could be on
that surface and they get exposed. So there possibly can be some residual
kill for some days after the initial treatment for mites not on bees. And
some mites transfer to other bees so would come in contact with OA on that
bee if the OA is persistent.

But the emerged bee mites on the bees will be there for 5 or more days, so
they get hit with the next treatment (early in the am with all the bees in
the hive) and start all over again. Then you have the question of how many
get into cells after 5 days but before the seventh? Not all the mites leave
the bees after 5 days. So you would have a small mite drop (only emerging
mites not on bees if the residual OA does kill them) until you treat
again.But the mites that leave after only 5 days have to crawl on the wax
to find a larva at the right stage. More OA contact.So the issue would be
-how many mites make it to a cell between the fifth and seventh day? My
guess is not many since it is at the beginning of the period when they move
to the cells (5-11 days). So there may be a higher survival rate for the
mites (but my guess is not very high) treated at seven day intervals
compared to 5 day. i would also guess that there is not much difference
between the four and five day interval mite survival.

I can see why the 5 day cycle is the one that comes with the vaporizer
instructions (3x5) since it fits the Varroa life cycle worst case. You are
only a day off of Nancy and Randy's 4 days (which is insurance) and still
cover the 11 days with more overlap.

I am sure that somewhere there is a study on the different intervals and
what happens, just I have not run across it.

It seems that "when in doubt, follow the instructions" still applies- it is
just that I like to know why. So 3x5 it is since it seems to work, fits the
Varroa life cycle and is the best compromise.But I do like that 3x7.

Bill Truesdell
Bath, Maine

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