Timber suffers from various biological damages. Recent efforts aim on nature-friendly sustainable technologies of wood protection to replace classical synthetic agents having usually negative impact on many non-target organisms including man. This research investigated the biocidal effectiveness of lavender oil (LO) in protecting the Norway spruce (Picea abies) wood against the termites Reticulitermes flavipes and the brown-rot fungus Rhodonia placenta. Following, selected physical characteristics of spruce wood treated with LO were evaluated: colour changes, roughness, surface wetting with water and surface free energy (SFE). Experiments showed that LO increased the resistance of spruce wood to termites nearly to the level of its treatment with commercial biocide based on trivalent boron and quaternary ammonium salt. The additional hydrophobic treatment of wood ensured its full termite-resistance even after artificial weathering in Xenotest and leaching in water according to EN 84, respectively. It shows a high potential of LO to protect wood against termites. Adversely, the effectiveness of 5% LO against rot was not sufficient. The colour of the oil-treated wood was preserved, its roughness increased slightly, and wetting and SFE led to a positive change, improving the adhesion of potentially applied coatings or adhesives for exterior exposures.
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