The graying of cedar shingles in a maritime climate--a fungal basis?

Abstract

Cedar shingling is used extensively on the exterior of buildings of Nantucket Island because it is resistant to damage and decay by the elements. Although often structurally sound for up to 30 years, cedar shingles weather to a characteristic gray in this maritime clime within weeks of their installation. In contrast, cedar shingles when weathered in more inland locations yield a brownish hue. A survey was conducted of fungal populations inhabiting cedar shingles from maritime and inland locales to assess whether fungi contributed to these differences in coloring. Aureobasidium pullulans, a black yeast, was recovered consistently in all weathered samples, both maritime and inland. No major differences were seen between the fungal populations from these distinct geographic sites. It was concluded that A. pullulans and other blue stain fungi from the shingles could be responsible in part for the coloration of weathered shingles, but did not apparently account for the differences in coloring of gray (maritime) and brownish (inland) shingles. This exercise demonstrates identifiable common deteriogens, and is readily adapted to general microbiology laboratory classes. The isolates are from common microbial niches, wooden posts, window pane putty, tile grout and paint surfaces, and give the student a feel for the ubiquitous influence of microbes. Journal of Industrial Microbiology & Biotechnology (2000) 24, 319–322.