Fungi Associated with Decay in Treated Douglas-Fir Transmission Poles

Decay was detected by cultural methods in 190 of 952 (approximately 20%) treated Douglas-fir transmission poles installed for up to 10 years in the northeastern United States. Preservative systems and treatments for the poles sampled were penta in petroleum oil, penta in liquefied petroleum gas, chromated copper arsenate, and ammoniacal copper arsenate. Isolations were made from various radial positions on several increment cores selected from the groundline zone and deep check vicinity for each pole. The decay was in early stages, often localized, and in many cases, detectable only by cultural means. The decay fungi, representing 19 identified species, were isolated primarily from untreated inner pole sections and at the groundline. Poria carbonica, a decay fungus known primarily from the western United States, and Poria placenta, were the two species isolated most frequently. Six of the nineteen species were in the monocaryon nuclear condition and identified by cross matching with known monocaryon isolates and subsequent formation of clamp connections. Decay frequency in the poles generally increased with check depth. The time of occurrence and location of the decay in many poles suggests that in some cases early decay may escape preservative treatment or becomes established shortly thereafter in the storage yard. Decay may also start shortly after installation and be associated with check development into untreated wood. The data suggest that pole preparation or treatment practices that would increase preservative penetration and reduce check development would minimize decay development.

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