Mark Pfeifer wrote:
" . . . anyone have ideas for a plane-friendly surface treatment to fill in
beetle tracks?"

Sawdust and glue, BLO, or shellac.  Mix up as a putty. Or stuff the hole with
dry sawdust and drip the liquid on. Might have to repeat a couple of times, it
may shrink down into the hole as it dries. Level when dry with a sharp chisel.
Tom ConroyBerkeley