As timbers or poles age in outdoor environments, the wood contracts during dry conditions and expands during wet conditions. The size and depth of the resulting cracks or checks that develope over time will depend on moisture content, the number of wet/dry cycles and the size and species of wood. These checks and other defects provide access for rot fungi and insects to untreated wood beyond the externally treated zone.

It is a fact that internal treatment of standing wood poles with repeated doses of fumigant or fungicide is effective in controlling internal decay and insects infestation. Cost/benefit studies indicate savings of $4 to $16 / pole/ year using pole replacement costs of $1000 and $3000 per pole respectively.

The cost/benefit studies refered to above exclude public liability considerations which may be substantial.

Re-usable plugs can result in a cost saving of approximately 90 cents/pole over the life of the pole when compared to treated wood plugs.