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Abstract
This research examined oil from the neem tree (Azadirachta indica A. Juss.) for its potential as an eco-friendly wood preservative. In contrast to expectations from the literature, according to which neem oil should be effective against insects and fungi, neem oil performed poorly as a preservative for Pinus radiata D. Don wood, which suffered significant mass losses in the bioassays. Using standard experimental procedures from the wood preservation industry, concentrations of 0.01, 0.1, 1.0, 2.5 and 5.0 percent neem oil in white spirit were bioassayed against five species of decay fungi. Additionally, concentrations of 0.01, 0.1 and 1.0 percent neem oil were bio assayed against two species of termites. It is concluded that neem oil can only be useful as a wood preservative if new, optimized formulations are sought, probably exploiting synergy with cobiocides.
Wood is a natural material containing cellulose and hemicelluloses, and can therefore act as food for a group of extremely active organisms, the xylophages, whose activity leads to both the decomposition of substratum and the reduction of material to its constituent elements. The xylophages of greatest economic importance are fungi and termites. Owing to the problems associated with wood biodeterioration, especially in tropical countries, treatment techniques using preservatives are often required if wood is to be used in construction (Cavalcante 1982, Costa 2000).
Concerns have been raised about the traditional preservatives used to protect wood because of the risk they may pose to both the environment and public health. Of particular concern are preservatives based on heavy metals such as chromium and arsenic, and those containing fluorine or creosote. Because the toxic compounds used often have low biodegradability, additional difficulties can arise in the post-use disposal of treated timber (Evans 2001, Hata et al. 2006).
A more environmentally friendly alternative may occur through the use of natural biocides, and some researchers have focused on the chemical components from the extracts of wood and other plants (Ohmura et al. 2000, Cookson et al. 2004, Rodrigues et al. 2012, Syofuna et al. 2012). This study considers the use of oil from the neem tree {Azadirachta indica A. Juss) as a potential eco-friendly wood preservative. Neem oil has low mammalian toxicity, while possessing biologically active compounds, such as azadirachtin and other limonoids...