Dear Jonathan
Our house was built in 1915 and the beams in the crawl space have holes of powder post beetles .We are in Ontario.
I put my finger on these beams and they seems solid still.
If I spray with the boracare do you think these beams could resist another 10 years?
But I found a  4×4 completely  transformed in dust is like sawdust- is like plaster  if I push the finger there is crumbling. I do not know what can be.
please help with a comment.

More on wood beam with bad insect damage