Fungi Colonizing Redwood In Cooling Towers: Identities and Effects on Wood Properties

Heartwood from coastal redwood [Sequoia sempervirens (D. Don.) Endl.] is very durable and is often used untreated in harsh environments, such as cooling towers of power or chemical processing plants. Wood in this environment is often attacked by soft rot fungi. Some wood users attempt to bolster protection by including additives, such as chromium, in the water. Examination of sections cut from a redwood cooling tower revealed that most pieces were colonized by a variety of Fungi Imperfecti, in spite of surface chromium levels that averaged 0.26 lb/ft3. Eleven species were isolated from the material; soft rot tests of these fungi indicated that all of the isolates were capable of causing Type 2 soft rot attack (cell-wall erosion). These fungi caused little or no weight loss on redwood specimens, but did damage less durable ponderosa pine sapwood. The results suggest that the redwood cooling tower was colonized by a variety of fungi; however, the combination of redwood extractives and a shallow chromium barrier appears to protect against soft rot attack