Preservative treatment produces an external layer of protection in Douglas-fir poles, but the development of deep checks as the wood dries after treatment can permit entry by fungi and insects. A variety of remedial treatments can arrest this decay; however, it is far more efficient to prevent checking. Kerfing represents one potential method for limiting the development of deep checks. In previous studies, examination of kerfed poles after 20 years in service revealed that only 2% contained viable decay fungi in the kerfed zone, while over 20% of similar non-kerfed poles contained viable decay fungi. Recently, over 5,000 kerfed and non-kerfed Douglas-fir poles ranging from 0 to 25 years in age were inspected. The presence of internal decay in these poles was generally low in comparison with previous reports. Several explanations are proposed for these differences.

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