PROTECTION OF WESTERN REDCEDAR POLE SAPWOOD BY SPRAY TREATMENTS

The ability of 30 oilborne and waterborne biocides to protect western redcedar (Thuja plicata Donn ex D. Don) sapwood from aboveground decay was assessed in pole sections and small blocks exposed on a test fenc e over 2- to 11-year periods. Many chemicals provided protection for t he first 2 years, but this protection declined rapidly thereafter, unl ike that provided by pentachlorophenol, the chemical previously used f or this application. Kathon 930, TBTO, and several other chemicals pro tected small blocks exposed for 5 years under severe leaching; these c hemicals appear appropriate for such applications. In addition, severa l others provided slightly lower degrees of protection and might be ap propriate if retreatments were made at intervals shorter than the curr ent 10 to 15 years.