I am not a pest control expert of any kind but I do have some very
specific requirements when I need to control pests.  I am very
sensitive to pesticides of all types.  I also hate mothballs because
they are toxic and stink.  The stink can persist for years.

The following is based on my personal experience and information
gleaned over the years, not on careful research or comparison of all
the alternatives.

One quick aside.  Although we often curse the moths that eat our
clothing we need to be reminded that the protein in hair and feathers
is very tough stuff and is not subject to decay nor is it eaten by
much of anything but the clothing moth.  I read an article some time
in the past that suggested if it were not for this moth, our planet
would be covered in a suffocating layer of hair and feathers since
they decay soooo slowly.

Moth balls or flakes are very effective and I think primarily serve
to deter adult moths, not to kill the larvae (unless you have such
a high concentration that it would kill you too) which are what eat
the wool or feathers.

Fumigating will kill pretty much anything and it is possible to
fumigate with something very low in toxicity and or with little
residue.  A professional should be able to tent you piano (or whatever)
kill the larvae and return it with little or no toxic residue.

It is even possible to kill anything that depends on oxygen for
survival by suffocating with carbon dioxide (CO2).  You can even do
this yourself.  You can make a huge bag out of thin pond liner material
glued with a suitable glue to create a bag with an open end.  CO2 is
about 1.5 times as dense as air.  Make the bag longer than necessary
to hold the piano and roll it in.  Roll up the open end and clamp it.
You will need to have in and out ports in the bag as well.

The CO2 should go in the bottom (slowly) and be exhausted at the top.
You can tell when the air is all exhausted by checking with a match:
when the exiting gas extinguishes a flame, it is CO2, not air.  Add
a little more just to be sure.  If you puff the bag up a little you
will know that it is not leaking if it stays puffed up.

Professional fumigators probably have ready-made bags suitable for
a piano.  You can also buy piano bags from Steinway made for shipping
pianos on cargo ships.  I have never seen one myself but I was told
about them by someone, I believe.

Then it is just necessary to keep the moths from returning.  Clothing
moths like it dark.  If you leave the piano open it is less likely to
attract them.  Moths do not like cedar oil nor do they like pyrethrins
or the synthetic form.  All of these are very low in toxicity to
humans.  The U.S. Army has been using them for years as a preferred
repellant for ticks.

Pyrethrins have a stronger killing action but the synthetic form
lasts longer, especially in sunlight.  Various horsefly sprays are
made with both of these and usually with citronella oil added as well.
I have been using these for many years to repel ticks on my pet
poodles.  I have had severe reactions to other tick sprays and
treatments but have not had the slightest reaction to the horsefly
sprays I have used.

High concentrations of cedar oil might corrode metals so do not slop it
all over the place.  It might be good to put a very inviting block of
solid wool felt in a dark corner of the piano as a test site to see if
re-infestation occurs.

An added benefit of using these sprays on your piano is that you will
not have any ticks or horseflies in it.

Best regards, Spencer Chase
Garberville, Calif.
http://www.spencerserolls.com/