The heartwood of Belian (Eusideroxylon zwageri) is highly regarded among the naturally durable Malaysian hardwoods, and is therefore a choice timber for soilcontact use in the humid tropics such as untreated telecommunication poles, fence posts and railway sleepers. The high microbial resistance of the wood is evidenced by the mere superficial degradation observed in some pole samples after 20 years of service in Sarawak, where electron microscopic studies have reported an unusual type of fungal attack in the cell walls of fibres and parenchyma. Additionally such examinations of Belian stakes from Sabah have confirmed the occurrence of widespread tunnelling bacterial attack on the heartwood surfaces. Other typical patterns of fungal or bacterial degradation have not been observed in Belian wood. The information on microbial decay of Belian heartwood available to date is reviewed and patterns of decay illustrated. Limited information is also available on the fungal resistance of the sapwood and termite resistance. The inherent anatomical and chemical characteristics of Belian wood could conceivably explain the observed superficial microbial degradation patterns and the, otherwise, extreme natural immunity to decay of this timber species.

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