The rate of decay of Pinus radiata was evaluated using four different field test protocols at a site near New Plymouth, New Zealand. The average Scheffer index was 86 over the five year period of testing. The field tests were an in-ground stake test (AWPA Std E7-01) and three above ground tests – lap-joint (AWPA Std E16-98), decking (AWPC protocol) and ground proximity tests (AWPA Std E18-06) Two wood preservatives were used, ACQ and an experimental formulation containing the azole propiconazole. Each preservative was tested at three retentions, a full retention or rate and then ½ and ¼ this retention. All trials included untreated Pinus radiata control samples. The most graphic differences among tests were observed in untreated samples. The in-ground stake test displayed the greatest initial rate of decay with untreated stakes failing after 2 years. However the most reliable early indicator of decay was observed in the decking test where samples were laid on untreated bearers. In a parallel decking test where samples were laid on treated bearers they remained sound for 3 years then declined rapidly in years 4 and 5. Based on untreated and preservative treated Pinus radiata the results in the present study indicate a ranking for most rapid to least rapid for above ground protocols of: decking test on untreated wood > ground proximity > lap-joint = decking on treated wood.

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