First I think the use of borax is best before the borers are in.
What I did, after a massive borer attack on my elm and ash pile:
Put them (about 100 worked down staves) in a huge cask, so the lower half was in the cask, a huge plastig bag over the upper half and taped to cask, inside the closed atmosphere a pot of ammonia. This setup was left for a few days, all bugs and borers were killed.
Another possible setup:
Pack all your staves in a huge plastic bag, tape in a pipe to the exhaust of your car, let the motor run a few minites till the bag is full of the fumes. Never tried this but I think it should work.
Good luck Chuck!