The Australian National Art gallery just found the same problem with
the wood frames of a number of famous European artworks sent here for
an exhibition.  The paintings were sent out and fumigated to kill any
nasties.

I'd suggest you ask a pest control company for advice.  I believe they
can enclose the instrument in a large plastic bag, seal it off and spray
in a fumigant gas.  You would need to be sure the chemicals don't
attack ivory, plastic, etc., but if they can do it for priceless art
treasures it should be okay for pianos.

Perhaps you could achieve the same result yourself at less cost.  There
are available in stores insect killer pressure pack "bombs" which are
used to fumigate an entire house.  Check if it states on the label
whether it will kill wood worm and borers.

Once one of these "bombs" is fired off you need to leave the house for
a couple of hours.  So, you could use wrap and seal the instrument in
plastic sheet with a canister inside, trigger it -- and still leave the
house!

Colin MacKinnon

 [ I'm trying to recall the name of the gas; is it ethylene bromide?
 [ Whatever it is, it's lethal!   -- Robbie