The only means to effectively treat and sterilise timber is by using diffusible wood preservatives that have the ability to move deep into the wood cells colonised by fungi.
Barrier treatments rely on chemical barriers to protect the critical groundline zone. In this treatment chemicals such as copper naphthenate are applied to the external section of the pole immediately below groundline with the intention that the treatment forms a barrier against any decay fungi spores from entering the wood from the surrounding environment. This process is most suited to new wood where fungal spores have not been established in the wood structure and the chemical barrier can prevent new infections. Field tests have shown this process very ineffective when applied to poles that have been installed for a longer period of time where invariably these poles have been colonised by existing fungi entering through cracks or checks and inaccessible to these barrier type treatments.