Sep 17, 2013 - 10:29 AM
The best thing to use to toxify the walls for a long period of time is Timbor.
Don't be mislead by the packaging. Timbor is a wood treatment, but it is also an insect treatment. It is similar to Boric Acid. Excellent long term control of bugs. termites, wood rot, etc.
It can be dusted dry into the wall voids, or diluted with water and sprayed. Any pesticide will do the job, but nothing will last as long as Timbor.