Naturally durable heartwood: evidence for a proposed dual defensive function of the extractives

We previously proposed that extractives in highly durable heartwood may pro tect wood against fungal colonization and subsequent degradation by dual me chanisms: the extractives have some fungicidal activity and are also free r adical scavengers (antioxidants). In short-term laboratory decay tests usin g two different wood species and decay fungi, the antioxidant 2,4dimethyl-d i-tert-butyl-4-methylphenol (BHT) alone had little or no preservative effec t. In contrast, the combination of BHT with different organic commercial bi ocides always showed an increase in efficacy compared to the organic biocid e alone. Consequently, we conclude that the combination of a commercial ant ioxidant and biocide is synergistic. This implies that extractives may prot ect wood by more than simply being fungicidal. (C) 2000 Elsevier Science Lt d. All rights reserved.