Skip to content
Accessible Unlicensed Requires Authentication Published by De Gruyter August 19, 2011

Relative fungal efficacy results from the soil block test with a long incubation period of three commercial copper wood preservatives

Tor P. Schultz and Darrel D. Nicholas
From the journal


Development of new wood preservative systems is a lengthy and expensive endeavor. This study examined soil block experiments with a longer incubation time than typical to make the test harsher, using commercial particulate copper azole (PCA), soluble copper azole (CA-C), and soluble alkaline copper quaternary (ACQ-D) systems. Both the CA-C and PCA systems performed poorly compared to ACQ-D with two copper tolerant fungi, even at retentions well above the specified ground-contact residential level, i.e., Use Category 4A (UC4A). With the one copper sensitive fungus examined, PCA and ACQ-D prevented decay at about half the UC4A retention. To compare these laboratory efficacy results, data from an outdoor accelerated post test with a copper tolerant fungus gave efficacies of ACQ > CA-C >> PCA, with PCA having significantly more decay than the two soluble copper systems. Further confirmation was obtained from recently published E7 stake data conducted at a site with extensive copper tolerant fungi, which suggested that ACQ performed better than PCA and CA-B after about 3 years of exposure in agreement with the harsh soil block results with the two copper-tolerant fungi. Conversely, results from four other sites without a history of extensive copper tolerant fungi are interpreted that all three systems generally performed adequately, which is compatible with the soil block test with the one copper sensitive fungus examined.

Corresponding author. Forest Products Laboratory/FWRC, Mississippi State University, Mississippi State, MS 39762, USA Phone: +1-662-325-3136 Fax: +1-662-325-8126

Received: 2011-3-29
Accepted: 2011-7-15
Published Online: 2011-08-19
Published in Print: 2012-02-01

©2012 by Walter de Gruyter Berlin Boston