Performance of copper based biocides in potentially copper tolerant soils

Graduation date: 2002Copper is an excellent biocide which has a long history of usage for protecting wood from deterioration, but some organisms have developed tolerance for this chemical. Copper tolerance among wood decay fungi is a poorly understood phenomenon that is gaining importance as cofactors such as arsenic and chromium are removed from industrial wood preservatives. Currently, the occurrence and methods for detecting copper tolerance are varied and relatively subjective. This study used a quantitative, non-destructive and automated method for testing the ability of a potentially copper tolerant soil to degrade copper treated wood in vivo. Flexural stiffness properties of small western hemlock samples treated to two retentions with six common wood preservatives were measured to assess microbial damage over one year of exposure to Oregon soil in an active hop yard. While mean control stiffness of untreated controls declined markedly over one year, all preservatives conferred a high degree of protection to the samples over the test period. Microscopic investigation revealed that a moderate amount of soft rot and general decay existed in some of the preservative treated stakes, while the controls showed widespread damage from both soft rot and general decay. The results indicate that while the exposure period allowed fungi to colonize treated wood, these organisms had not developed to the extent that they affected properties of wood treated with copper-based biocides