Accelerated above-ground decay testing in Australia and New Zealand

• The fastest above-ground fungal field test out of 12 examined was the rot box.
• The most reliable H3 test designs provided habitat for a wide range of fungi.
• Results in the Accelerated Field Simulator gave poor correlation to the field.
• Pre-inoculation with Gloeophyllum abietinum not Oligoporus placenta gave good results.
• The improved designs have halved H3 decay testing times at Innisfail in the wet tropics.

The aim of this research into above-ground (H3) fungal field testing was to find a method that would shorten the time required for evaluating new preservatives and protection systems. A trial was installed at two sites in Australia and one in New Zealand, as well as in two indoor accelerated field simulators. One-quarter H3 retentions were installed, including CCA as positive controls, as first results suitable for preservative registration occur when these reach 70% soundness. Twelve test methods were examined, some established and others developed for the project. In two methods, feeder blocks pre-inoculated with laboratory-raised fungi were placed next to test specimens in an effort to accelerate decay. The treatments examined were CCA, alkaline copper high quat (AChQ), azoles, kerosene, TBTN, and water. Untreated Corymbia maculata heartwood was included for natural durability. Inspection was annual for 4 yr. The fastest tests were those that held moisture for longer periods in test specimens and were the “rot box” at Innisfail, followed by the ground proximity, deck-on-ground, and “embedded” tests at this high-rainfall location. The most reliable tests giving expected relative order of failure were those allowing diversity of fungi rather than those that became dominated by a few, and included those placed close to the ground or with increased volume of untreated wood substrate in frames. Reliability was also influenced by duration of the trial. Pre-inoculation with Gloeophyllum abietinum gave more representative results than pre-inoculation with Oligoporus placenta.