Robert from Arlington, Tx writes
I am pretty sure that I have a powderpost beetle infestation in a window frame that was stained 5 years ago but not sealed as far as I know. Another website says this: "However, stain by itself will not stop Boracare from penetrating. If it has weathered for a year or two, than applying Boracare before you next apply some stain would be best." So would it be worth a try to treat with Boracare before going to the trouble of stripping and restaining the wood?