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.
Fungicides for Wood Protection - World Viewpoint and Evaluation/Testing in Slovakia
Hardwoods (e.g. ash, beech, oak, poplar) and softwoods (e.g. fir, pine, spruce) consist of various types of cells: vessel elements, tracheids, libriform fibres, axial parenchyma cells, ray parenchyma cells, epithelial cells, etc. These cells exhibit various orientations in relation to the standing tree and provide various functions, such as, imparting mechanical strength, acting as water-conducting elements, or functioning as storage cells. Wood cells, their cell walls and lumens have typical shapes and dimensions. Cell walls usually consist of primary and secondary wall layers which are made up from basic natural polymers: cellulose, hemicelluloses and lignin. Extractives of durable wood species (such as terpenoids, tropolones, stilbenes, flavonoids or chinones) are usually present in the cell lumens, or sometimes even in the cell walls (Fengel & Wegener 1984). Wood is a natural organic material and as such it can be degraded by biological agents: bacteria, fungi and insects. The use of wood is thereby limited by its susceptibility to organisms that may damage its structure and deteriorate its properties. Wood-destroying fungi, such as brown-rot (Serpula lacrymans, Coniophora puteana, Antrodia vaillantii, Gloeophyllum trabeum, Lentinus lepideus, etc.) and white-rot (Trametes versicolor, Trametes hirsuta, Schizophyllum commune, etc.) basidiomycetes, or soft-rot (Chaetomium globosum, Monodictys putredinis, etc.) ascomycetes, destroy polysaccharides (cellulose and hemicelluloses) present in the cell walls. They may also, in different degrees, degrade the lignin (Arantes et al. 2010, Schmidt 2006). Fungi attain the depolymerization of polysaccharides by producing various types of hydrolytic enzymes, e.g. degradation of crystalline cellulose is achieved using etracellular endo-1,4-s-glucanases, exo-1,4-sglucanases, and 1,4-s-glucosidase. Brown rot-fungi which do not have exo-1,4-sglucanases use the low molecular non-enzymatic Fenton chelator-mediated system consisting of oxalic acid, iron cations and hydrogen peroxide (Eriksson et al. 1990, Goodell et al. 2007, Hastrup et al. 2010, Messner et al. 2003). Rotten wood has lower density and lower strength (Reinprecht 1992, Wilcox 1978). In parallel to the changes above, rot-fungi also change the moisture, colour, acoustic and other properties of wood, with an expressive influence on wood quality. However, these fungi can only degrade the structural components of wood in situations when its moisture content (MC) is 20 % or more (Carll & Highley 1999).
Control of reflective cracking
The first is 'fatigue' cracking of the layer. This type of cracking is the result of the application of loads on the pavement and is controlled by appropriate thickness design which 'ill not be discussed in detail here. Thickness design includes not only the design strength and thickness of the stabilised, but other design elements such as delaying reflection cracking, or limiting stresses in the stabilised layer, by adopting a minimum thickness of overlying material. This may include an unbound layer utilising the 'upside down' pavement approach. The actual thickness required of the overlying material varies but for example PIARC (Ref.1) recently reported when the thickness of coated materials exceeds 20 cm the emergence of shrinkage cracks at the surface is generally uncommon; when it is 15 cm thick, the cracks emerge at the surface, but do not shorten the life of the surface course, especially if they are sealed. This experience has been gained 'with legal axle loads of 130 kN, considerably greater than the Australian legal axle load.