Sarah, in the SF bay area, reports a hive with reasonably significant mite
counts and says "Do I retreat immediately with Apistan?  For the record I
had the Apistan in for 51 days and followed the directions.  The hive in
question was treated with four strips."

Sarah, you also reported that you had purchased the Apistan strips a year
before you had used them, but kept them out of the sun and in the original
package until use.  You might want to call the manufacturer, (Wellmark
International 800-248-7763), but I am reasonably certain they will tell you
that under those conditions the strips were "as good as new".

  Unfortunately, it seems that you have mites resistant to fluvalinate, the
active ingredient in Apistan.  (That is not terribly surprising, given your
location and the fact that hundreds of thousands of hives are annually
imported into the area for almond pollination.)  Thankfully, alternative
products are available.

One is Checkmite(tm).  You have heard much about this from this forum.
Personally, I only consider using it as an absolute last resort...and even
then I might decline.  The active ingredient is a very dangerous chemical.
Further, as of the last advertisement I have it is not approved for use in
California.  If you wish to check on that or wish more information call Mann
Lake (800-233-6663).

The other is a formic acid gel.  Unfortunately, I cannot recall the brand
name.  My understanding is that this is going to only be sold in a box
containing 24 packages, for reasons having to do with ICC shipping
regulations.  With only two hives, you would have to share with a friend or
perhaps your local bee club is planning on buying and distributing to
members (which is perfectly legal).  If this is not available now, it will
be very soon.  Call Betterbee, Inc. for more information (800-632-3379) from
nine till five, Eastern Time.

While you are waiting for the gel, assuming that is the route you wish to
pursue, with only two hives you can practice some Integrated Pest
Management.  On a day that is above 50, pull the frames and gently open the
sealed drone cells.  A capping scratcher will do a good job, but rather than
buy one, use a kitchen fork.  Just drag the tines across the tops of the
cells with enough pressure to make a hole in each.  Do this every week or
ten days until your gel comes and you use it for treatment.  All you need do
is put a tiny hone in each cell...any size hole will do.  Once the hole is
there the bees will uncap the cell and dispose of the larvae.  The adult
mites present might or might not be destroyed, but any mite larvae or eggs
will be destroyed.

Good luck, and I hope I have helped.

Lloyd
Lloyd Spear, Owner, Ross Rounds, Inc.  The finest in comb honey production.
www.rossrounds.com