Wood decay fungi from New Zealand ‘leaky’ buildings: PCR identification and laboratory decay tests of wood preservative-treated Pinus radiata (Part 1)

IRG/WP 07-10620

D Stahlhut, R L Farrell, R Wakeling, M Hedley

Fungi colonising Pinus radiata D. Don framing timber of ‘leaky’ New Zealand buildings were isolated to produce pure cultures. Mycelia from these cultures on agar media were collected to extract DNA. To identify the fungi to the species level, polymerase chain reaction (PCR) with primer pairs ITS1-F and ITS4 were performed followed by sequencing of the internal transcribed spacer (ITS) region. Identification was by BLAST (Basic Local Alignment Search Tool) search on sequences in GenBank. Gloeophyllum sepiarium, Oligoporus placenta and Antrodia sinuosa were identified with a 98-99% match. With identification, these three decay fungi and a standard decay fungus (Coniophora puteana) were used to determine the effectiveness of currently used wood framing preservatives under laboratory conditions before and after a standard leaching regime. Pinus radiata blocks were treated with water based Boron and Copper Azole and solvent based IPBC and Propiconazole/Tebuconazole (1:1) preservatives and exposed to these four basidiomycetes for 12 weeks under laboratory conditions. Weight loss of up to 55% for preservative-treated samples, up to 62% weight loss for leached samples and up to 58% weight loss for untreated samples was recorded. Additionally, well defined dose responses and approximate toxic thresholds were obtained for all preservatives tested. Results suggested that the minimum IPBC retention specified by Hazard Class 1.2 of NZS3640:2003 (0.025% m/m) is on the low side, and demonstrated complete loss of efficacy of boron at 0.4% m/m boric acid equivalent (BAE) after the 2 week leaching regime. Results further showed that PCR techniques comprise a very useful tool for fungal identification and are expected to provide a reasonably definitive list of causative decay fungi as the survey of ‘leaky’ buildings continues. This study gives a first overview of fungi occurring in New Zealand houses, demonstrating that the test fungus Antrodia sinuosa was more difficult to control with Propiconazole/Tebuconazole at retention 0.007% m/m than the known tolerant fungus Oligoporus placenta, that Boron at Hazard Class 1.2 retention of 0.4% m/m BAE was not toxic to all fungi and that Gloeophyllum sepiarium appeared likely to be important in New Zealand ‘leaky’ buildings and was susceptible to all wood preservatives.

Keywords: ‘leaky’ buildings, Pinus radiata, CuAz, Boron, IPBC, Tebuconazole/Propiconazole, PCR- polymerase chain reaction

Conference: 07-05-20/24 Jackson, USA

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