I found this article about the topic of wood deterioration in aircraft. The
short version I got was that it's dampness related, cant be prevented with
paint and varnish, but can be prevented with other preservatives, and requires
visual inspection to keep on top of, and dont store plane outdoors, and most
preferably in heated hangar.
http://www.mooneymite.com/articles/dryrot/dryrotkills.htm
"In all but the driest of climates it is impossible to protect wood structures
in aircraft from being attacked by fungus to some degree. But there are a
number of preventive actions which can be taken to inhibit the decay process1.
Store wooden aircraft in a hangar if possible, preferably a heated hangar,
especially in winter. Admittedly this is becoming increasingly difficult today,
as hangar space becomes more precious and many owners of wooden airplanes are
being forced to settle for an outdoor tie-down area.2. There are a number of
good wood preservatives available today, such as copper napthenate and
pentachlorophenol. Properly impregnated into the wood, these will prevent or
retard deterioration. Incidentally, regular paint and varnish do not
necessarily ward off wood rot. When you paint or varnish you can actually seal
many spores to the surface of the wood, and moisture Is capable of penetrating
the painted surface under humid conditions.3. Most wood-constructed airplanes
have some drain holes at the bottom of each wood component, so that any water
which has accumulated there can drain out. It is imperative that drains be kept
open and unclogged so that they can perform their invaluable function of
allowing water to flow out, Make certain you know the location of all the drain
ports on your aircraft, and inspect them at every preflight check."
