A six-year ground proximity trial of TRU-CORE treatments at Innisfail, Queensland
This article describes an H3 (above ground outdoor) ground proximity field trial that compares the performance against decay fungi of TRU-CORE (also known as the Buffered Amine Oxide Enhancement System) Copper Quat (CQ) with CCA and commodity Alkaline Copper Quat (commodity-CQ) treatments, all in Pinus radiata. The retentions achieved reflected commercial practice, where higher mean retentions are sought to ensure that the less treatable timbers within a bundle still meet minimum requirements. Two sets of TRU-CORE CQ test specimens were prepared, one specifically for this trial and the other several years earlier under the supervision of Scion. The field test was installed at Innisfail in the wet tropics, and inspected annually for six years, with ratings given according to both the CSIRO and AWPA scales. Untreated radiata pine was severely decayed after two years and rated 0.0 after four years. After six years, the relative order of performance, starting with the best, was TRU-CORE CQ Scion (mean AWPA rating 9.4), TRU-CORE CQ (9.2), CCA (7.3) and commodity-CQ (7.1). The commodity-CQ treatment, with ten replicates, included two specimens failed (rating 0.0); however, cause of failure was not apparent from retention results, as both test specimens were amongst the top half in terms of retention in full cross-section and core (inner ninth). While knots were included in some treated test specimens, they did not become focal points for decay.