Ten Essential Oils for Beech Wood Protection - Efficacy Against Wood-destroying Fungi and Moulds, and Effect on Wood Discoloration
This work analyses the anti-fungal efficacy and stability of 10 essential oils, as well as their colour stability, in wood. The efficacy of oils against the decay fungi Coniophora puteana and Trametes versicolor as well as the moulds Aspergillus niger and Penicillium brevicompactum was evaluated first on filter papers treated with 1, 3.5, 10%, or 100% concentrate, and then on beech wood treated with 10% solutions. Accelerated ageing of treated beech samples was done before mycological tests and consisted of heating, leaching followed by heating, and Xenotest followed by heating. The highest growth inhibition of moulds and C. puteana was caused by thyme, oregano, sweet flag, and clove oils, while the savory and birch oils were less effective. These oils are potentially useful for wood protection against brown-rot fungi and moulds, mostly in interior conditions. The essential oils had only a negligible effect against the white-rot fungus T. versicolor, which was more apparent after previous ageing of wood. Some essential oils with a yellow tone (birch, oregano, sweet flag, savory, and tea tree oils) significantly changed (p<0.05) the natural colour of beech wood, but the new colours were relatively stable and underwent only mild changes after accelerated ageing in Xenotest.
Moldicidal properties of seven essential oils
When wood and wood products are exposed to moisture during storage, construction or while in-service, mold growth can occur in 24 to 48 hours. Mold growth could be suppressed or prevented if wood was treated with an effective mold inhibitor. The objective of this study was to evaluate the mold inhibiting properties of natural plant extracts such as essential oils. Seven essential oils were evaluated for their ability to inhibit growth of Aspergillus niger, Trichoderma viride, and Penicillium chysogenum on Southern yellow pine (SYP) specimens that were either dip-treated or exposed to volatiles of the test oils. Dip treatment with thyme or geranium (Egyptian) oil inhibited growth of test fungi for 20 weeks. Vapors from dill weed oil also inhibited all test fungi for at least 20 weeks when the vapor source remained in the test apparatus. Essential oils may be useful as moldicidal surface-treatments or fumigants for wood and wood products.
Resistance to decay fungi of ammonium borate oleate treated wood
Ammonium borate oleate molecule (ABO) produced from reaction between boric acid, ammonia and oleic acid was tested as wood preservative treatment against brown and white rot fungi according to European standards. This compound was prepared according to a previous study which has proved existence of synthesis reaction and effectiveness against termites (Lyon et al. 2007b). Four solutions of ABO in ethanol were then produced and impregnated sapwood specimens of Beech and Pine exposed to fungi Coniophora puteana and Coriolus versicolor. Efficiency thresholds were found in each case except for Pine samples exposed to Coniophora puteana. Combination of the biocide effect of boron, and the water repellence of fatty acids allowed to provide resistance of leached wood specimens against fungi.