Decay and Termite resistance of extractives-free naturally durable wood

Diyana, Mohd Dasrul Davedass (2015) Decay and Termite resistance of extractives-free naturally durable wood. [Final Year Project Report] (Unpublished)

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Abstract

Natural durability of wood is one of the factors that contribute to resistance of wood species towards the attack from microorganisms, such as fungi, termites and other bio-deteriorating agents. The purpose of this study was to determine the decay resistance of durable species which are Eusideroxylon zwageri, Potoxylon melagangai and Vatica oblongifolia towards fungi and termites attack with and without the extractives content. A total of 42 wood blocks were cut into 10 mm cubes for each of the species. The extraction method was done with 21 blocks randomly chosen from each species by using Soxhlet extraction apparatus according to ASTM D1105-96 with minor adaptation. The solvents used in the extraction process were toluene, 95% ethanol and distilled water. For soil block test, two types of fungi were used, which were Trametes versicolor (white rot fungi) and Coniophora puteana (brown rot fungi). The wood blocks were exposed to Trametes versicolor for eight weeks, while to Coniophora puteana for four weeks. All of the samples showed higher percentage of weight loss for the extracted wood, than the unextracted wood. The termite resistance attack was conducted according to ASTM Standard D3345-74 (Reapproved 1999) and the exposure was done in the duration of one week. The wood blocks were exposed to 45 workers and 5 soldiers of Nasutitermes sp. in a Beatson jar. Potoxylon melagangai showed the highest weight loss at 0.6% for the extracted wood compared to Vatica oblongifolia, with 0.28% and Eusideroxylon zwageri with 0.4%. For the unextracted wood, Eusideroxylon zwageri showed the least susceptibility to termites, with 0.3%, followed by Vatica oblongifolia, 0.3% and Potoxylon melagangai with 0.2% of weight loss, respectively. Although extraction of extractives reduced decay resistance of the three wood species, the extractive-free blocks could still be considered resistant. This study showed that the high resistance of Eusideroxylon zwageri, Potoxylon melagangai and Vatica oblongifolia to both decay fungi and termites attack is due to the presence of toxic extractives. However, extractives are not the sole factor which contributes to decay resistance of the three durable wood species.

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