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Effect of test site, preservative and wood species on decay type Glenbervie pastoral and radiata pine forest sites
2000 - IRG/WP 00-30248
Pinus radiata stakes were treated with 0.8, 1.2, 1.8, 2.7 and 4.1 kg/m3 of CCA and Fagus sylvatica with 2.7, 4.1 and 6.1 kg/m3 of CCA. Both wood species were also treated with equivalent retentions of a copper plus triazole preservative (CT) (0.89, 1.3, 2 and 3 kg/m3 of copper for pine & 2.5 and 4 for beech) and chlorothalonil plus chlorpyriphos in oil (CC) (1.4, 2.1, 3.2 and 4.8 kg/m3 of chlorothalonil for pine and 3.2 and 7.2 for beech). Furthermore, P. radiata was treated with ammoniacal copper plus a quaternary ammmonium compound (ACQ) (0.8, 1.1, 1.7 and 2.6 kg/m3 copper) and a 60/40 mixture of high temperature creosote plus oil (C) (18, 27, 41 and 61 kg/m3). Treated and untreated stakes were exposed in the ground at 13 sites in New Zealand and Australia for between 4 and 6 years. This paper reports the significance of site, timber species, preservative and its concentration and time of exposure, on extent and type of decay, at two sites in Northland, New Zealand. The two sites were adjacent (200 metres), appeared to have essentially similar clay loam soil and climate but one was pastoral and the other was situated within a radiata pine forest. Most types of decay reported in the literature, were observed in this study but other undescribed or only partially characterised types were also found. The decay types found differed between test sites, preservative and timber species. The significance of tunnelling hyphae, which often caused severe decay of wood treated with the higher retentions of various preservatives, appears much greater than the prior literature would suggest. For pine the highest retentions of CC, CT and ACQ gave at least equivalent performance to the reference standards creosote and CCA, after approximately 5 years, at both test sites. For beech CC and CT both gave superior protection to CCA, at both sites. All the preservatives tested exhibited some weaknesses in terms of resistance to the various decay types observed.
R N Wakeling


Effect of test site location on in-ground preservative performance after 6 years
2001 - IRG/WP 01-20231
Pinus radiata test stakes were treated with 4.1 kg/m3 of CCA and Fagus sylvatica with 6.1 kg/m3 of CCA. Both wood species were also treated with a copper plus triazole preservative (3 kg/m3 of copper) and chlorothalonil plus chlorpyriphos in oil (4.8 kg/m3 chlorothalonil). Furthermore, P. radiata was treated with ammoniacal copper plus a quaternary ammonium compound (2.6 kg/m3 copper) and a 60/40 mixture of high temperature creosote plus oil (61 kg/m3 creosote). Treated and untreated stakes were exposed in the ground at 13 sites in New Zealand and Australia for approximately 6 years. Preservative performance was significantly affected by site and there was a site-preservative interaction effect where decay hazard at a given site was dependent on preservative treatment. For pine, chlorothalonil plus chlorpyriphos, copper-azole and ACQ gave at least equivalent performance to the reference standards creosote and CCA, after approximately 6 years, at the majority of test sites. For beech, chlorothalonil plus chloropyriphos and copper-azole both gave superior protection to CCA, at the majority of test sites. In general, the results suggest that it is possible to select 3 - 4 sites that collectively pose a diverse decay hazard, representative of the majority of situations encountered by wood in service.
R N Wakeling