Blue Staining in Ponderosa Pine Sapwood At Moderate and Low Temperatures

Unexpected blue stain in solidly piled pine lumber stored during cool autumn weather in central Oregon prompted tests of the ability of local staining fungi to grow and discolor wood over a range of moderate and low temperatures. Small boards of pine sapwood were inoculated with staining fungi, then incubated in solidly piled bundles at temperatures ranging from 28?C (82?F) to 3?C (37?F) and inspected periodically for stain. An isolate of the fungus Ceratocystis pilifera was cultured on malt agar to measure its growth rates over the same range of temperatures. Respiration of living wood cells and organisms did not provide a heat source for fungi infecting the bundled boards. The isolate of C. pilifera, which had fruited at 3?C (37?F), grew fastest at 22?C (73?F) on agar but caused greatest staining in wood at 8?C (45?F). Optimum temperature for staining by this isolate was less than previously reported for the species. Results indicate that this isolate can cause degrading stain in solidly piled, pine sapwood lumber stored 1 to 2 months at 3?C (37?F) to 8?C (45?F).

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