Soft-rot control in hardwoods treated with chromated copper arsenate preservatives. Part 3: Influence of wood substrate and copper loadings

IRG/WP 2100

M A Hulme, J A Butcher

The hypothesis is proposed that hardwoods need more chromated copper arsenate (CCA) than softwoods to protect them from soft-rot attack mainly because hardwoods are more readily consumed by soft-rot fungi. Simple model systems, using copper-supplemented agar or groundwood pulp treated with CCA showed that fungi tolerated more toxicant (copper) as more available substrate (malt) was provided. Soft-rot tests with CCA-treated hardwood blocks provided typical dosage-response curves when results were expressed as a ratio of substrate to toxicant (wood to copper). Furthermore, hardwoods needed 10 to 20 times more copper as CCA than softwoods to prevent soft-rot attack. When CCA was substituted by ammoniacal copper arsenate in 5 hardwoods, similar threshold values for soft-rot attack were obtained in terms of a wood-to-copper ratio. Hence, CCA may be behaving poorly against soft-rot fungi in our hardwood specimens mainly because the substrate contained too little copper. The practical implications of these results are discussed.


Keywords: AGAR PLATE TESTS; CCA; COPPER; GROUNDWOOD PULP DISCS; HARDWOODS; CHAETOMIUM GLOBOSUM; GLOEOPHYLLUM TRABEUM; HUMICOLA; RETENTION

Conference: 77-09-26/30 Noordwijk aan Zee, The Netherlands


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