Efficiency of natural wood extractives as wood preservatives against termite attack

A Syofuna,A.Y Banana,G Nakabonge

doi:10.4067/s0718-221x2012000200003

Abstract

Wood extractives play a major role in the protection of wood against termite and fungal attack. Wood extractives from three hard wood species of Milicia excelsa, Albizia coriaria and Markhamia lutea that are known to be very resistant against termite attack and fungal decay were studied to assess their role as wood preservatives in Uganda. Acetone, hexane and distilled water were used in the extraction of these compounds from the outer heartwood of the selected durable species. Extraction was done using a soxhlet extractor. e extractives obtained were used to treat Pinus caribaea and Antiaris toxicaria species known to be susceptible to termites and fungal attack. Treated blocks were then exposed to Macrotermes bellicosus termites in the eld. It was observed that wood extracts used as preservatives improved the resistance of less durable samples to termite attack by 50% compared to the controls. It was also observed that removal of extractives decreased resistance of the durable samples. It can be concluded that wood extractives contribute greatly to the protection of less durable wood species against termite attack.

Highlights

Wood being a biological material is readily degraded by bacteria, fungi and termites (Walker 1993, Schultz and Nicholas 2002)
Hinterstoisser et al (2000) noted that the content of extractives plays a key role in the prediction of the durability of wood. e concentration of extractives varies among species, between individual trees of the same species and within a single tree
E ect of treatment of less durable species with wood extractives Average weight loss for A. toxicaria and P. caribaea treated with Copper Chromium Arsenate (CCA) was 4.35 and 0.94 percent respectively a er exposure to termite attack

Summary

Introduction

Wood being a biological material is readily degraded by bacteria, fungi and termites (Walker 1993, Schultz and Nicholas 2002). Some wood species are resistant to these degrading agents while others are very susceptible to deterioration (Kityo and Plumptre 1997). Ese synthetic chemicals are expensive and o en harmful to the workers and the environment (Venmalar and Nagaveni 2005) Worse still, these preservatives are not readily degraded to harmless products and are not easy to detoxify. E resistance is mainly due to the accumulation of extractives in the heartwood, some of which are decay inhibitors (Kityo and Plumptre 1997). It is these extractives which render the heartwood unpalatable to wood destroying organisms. Hinterstoisser et al (2000) noted that the content of extractives plays a key role in the prediction of the durability of wood. e concentration of extractives varies among species, between individual trees of the same species and within a single tree

Methods

Results

Conclusion