Non-toxic methods of killing powder post beetles include kiln drying and applying a borate wood treatment. Since kiln drying is expensive, most people use borates. You need tools to strip the wood, a borate formulation and wood sealant.
Strip the wood
Borate formulations only work on unfinished wood. To make it effective on finished wood, first strip off the wood's paint, varnish or other sealant so the borates are able to penetrate the wood. You don't need to remove water-repellent stains on decks and wood siding, as borate formulations can penetrate these as long as the wood is pressure washed before borate treatment. Sand wood floors prior to borate application.
Apply the borate formulation
Spray, brush or soak the unfinished surfaces with borate formulation. As it dries, it soaks into the wood. It is odorless, non-toxic and remains effective for many years. It penetrates and kills the beetles inside, and also those entering and exiting the wood.
Prevent powder post beetle re-infestation
Once you have killed the powder post beetles with borate formulation, prevent further infestation by sealing lumber with paint, varnish or wax. Don't use old lumber from barns or woodpiles; only use lumber that has been kiln dried and treated. Since powder post beetles thrive in moisture, install moisture barriers in crawl spaces and under buildings.