Despite the wide use of essential oils in pharmaceutical and food industry as antimicrobial agents, their use as wood preservatives has not been fully explored. In this study, 12 essential oils were screened in nutrient medium for their antifungal activity against 8 common mould, sapstain or decay fungi. Subsequently, one essential oil, eugenol was evaluated for decay resistance in an agar/wood block tests using both unleached and leached cycles with radiata pine sapwood blocks. During the initial in-vitro screening trial, variability in the tolerance of the tested fungi towards the selected essential oil was apparent. Some of the essential oils such as geranium, cinnamon leaf and eugenol completely inhibited the growth of all test fungi at 0.5% w/v on nutrient medium, whereas, three essential oils; eucalyptus, olive leaf and kolorex® were unable to restrict the growth of any test fungi even at 1% w/v concentration. Durability test results on radiata pine confirmed the antifungal activity of eugenol but highlighted the leachibility of this compound from wood. Blocks treated with 3% w/v eugenol without a leaching cycle had less than 1% weight loss when exposed to all three tested wood decaying fungi, Oligoporus placenta, Coniophora puteana and Antrodia Xantha. However, blocks which were leached showed weight losses in the range of 13.40 to 23.12%. This study identified eugenol as a potential benign wood preservative for treatment of timber not exposed to severe leaching, e.g. New Zealand Hazard Class H1.2. However, to be used for higher decay hazard situations, further work for in-situ polymerization of eugenol to fix active(s) in wood will be required.

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