The development of preservative treatment recommendations for red oak and red maple glued-laminated timber bridge members

Several wood preservatives, especially some newer waterborne systems, use copper (II) as a deterrent to wood-decay fungi. However, several brown-rot wood-decay fungi exhibit tolerance to copper. Among these is the genus Wolfiporia, which was at one time included within the taxon Poria (Pres. ex Gray). This research investigated the variations of tolerance to copper among isolates using agar-screening trials. The basis for the characterization of isolates as high, medium, and low copper tolerant is the minimum inhibitory concentration (MIC) of copper that deters growth of the isolate. We also compared growth rates among isolates at sublethal levels of copper. The variations of tolerance to copper among isolates of W. cocos in agar media indicate that the difference in copper tolerance is statistically significant among isolates. Interpretative analysis of the radial growth indicates that there is not a strong correlation between rate of growth and tolerance to copper. The copper tolerance of various isolates can have a significant practical impact on the long-term performance oftreated-wood products or the bioprocessing of spent wood materials treated with copper-based preservatives.