Control of Brown Stain in Eastern White Pine with Reducing Agents

Brown stain, which often develops when eastern white pine (Pinus strobus L.) is stored in hot humid conditions and then kiln-dried, was practically eliminated by dipping the freshly sawn lumber in aqueous solutions of reducing agents before storage. Six of eight selected chemicals were successful in small-scale tests. Two of the best chemicals tested were a 5 percent solution of sodium thiosulphate and a 5 percent solution of sodium sulphite. Results were confirmed in kiln tests with 500 board feet of lumber. The addition of 0.5 percent of a quaternary ammonium compound improved the performance of the treatments against fungal mold during storage. It also improved brown-stain control when suboptimal concentrations of these reducing agents were used. The addition of sodium carbonate to the reducing agent may also improve control of brown stain. These chemicals were tested as replacements for sodium azide or sodium fluoride which, although effective, are unacceptably hazardous to human health.

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