Durability of Timber Species against Termite and Fungal Attack

Abstract

Timber, in its various forms, looses its natural durability and is subjected to several types of deterioration. It is susceptible to fungi, wood boring insects, subterranean termites (the most wood destructor pests in all tropical and sub-tropical regions of the world (Richardson, 1978), marine borers, etc. (Nicholas, 1973). Natural forests are vanishing at an alarming rate (estimated at 150,000 to 200,000 ha per year) as a result of the everincreasing demand for fuel wood as well as crop and grazing land, stimulated by rapid growing human and animal populations. Besides, the overlooked but significantly contributing to major causes of forest destruction is the severe degradation of wood and wood products by different biodeteriorating agents (Getachew Desalegn et al., 2003). The greatest threat to wooden houses in Ethiopia is posed by subterranean termites, which lead at least to partial rebuilding in 3-5 years (Wood, 1986). The undesirable consequence of repeated rebuilding is deforestation of the remaining scarce forests. In Canada, the average timber loss caused by insects and other wood deteriorating agents is 15-33% of the total volume of the country's wood consumption (Anderson, 1966). Decay/rot damage to farm and house buildings in the USA amounts to at least US $255 million annually, and including marine borers' damage it is US $500 million (Nicholas, 1973; Haygreen and Bowyer, 1989). The enormous damage by subterranean termites and other wood deteriorating agents on forest products in Ethiopia and throughout the tropics is an important economic consideration. Bio-deteriorating agents directly affect the forest products of the country and have negative influence on the poor economy of the rural people, who had to rebuild their wooden constructions frequently. Therefore, this serious problem needs solution to alleviate the destruction on wooden constructions. The need to preserve timber is to increase its service life. Therefore, research on the selection of effective preservative application and selection of naturally durable timber species used for construction purposes are the most important issues in many countries. Due to enormous destruction by different wood deteriorating agents in Ethiopia, different traditional protection measures and modem commercial preservatives were used in different parts of the country. Ash, plastic cover and used motor oil are among the traditional protection measures used to increase the service life of wood construction materials. Modem preservative (CCA) is used in telephone and electric transmission poles. Therefore, the main objectives of this study were to examine the most effective traditional and commercial wood preservatives and application methods and to determine the natural durability of the five timber species against termite and fungal attacks.