The combination of various organic biocides with commercial antioxidants generally increased the biocides’ efficacy 2-3 fold against wood-destroying fungi in short-term laboratory decay tests, and some positive results have been obtained after 2-4 years of outdoor exposure. The two antioxidants principally examined, propyl gallate and butylated hydroxytoluene, are low cost and, since both are food additives, benign. The biocides studied have either been examined as potential wood preservatives or are used in commercial wood preservative systems. The purpose of this paper is to: 1) briefly summarize our prior laboratory decay results; 2) briefly discuss results obtained so far from outdoor exposure tests, both above-ground and ground-contact exposure; 3) discuss differences in results between laboratory decay tests and the outdoor exposure data; and 4) propose a mechanism by which antioxidants could protect wood.

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