Marine exposure assessment of the natural resistance of a number of lesser known species of tropical hardwoods to teredinid and limnoriid borers
J R Williams, S M Cragg, L M S Borges, J D Icely
Naturally durable species of timber are used as an alternative to preservative treated timber for marine structures, but many species have not been evaluated for their potential for use in this environment. EN 275 specifies a 5-year test period - too long a period for screening tests to be economically viable. In this study, candidate timber species were selected for testing in the sea on the basis of their resistance to limnoriid attack determined in previous laboratory trials. Comparative resistance to teredinids was assessed by comparing the rate of deterioration observed in candidate species of lesser known hardwoods against that for greenheart and ekki, species of timber that have a proven track record for marine construction. Scots pine sapwood was used for comparison, as a non-durable timber.
At the site selected, rapid deterioration of Scots pine specimens due to teredinids and to Limnoria tripunctata occurred. Acaria quara, cumaru and uchi torrado (respectively Minquartia guianensis, Dipteryx excelsa and Sacoglottis guianensis) were not attacked over the six month exposure period, whereas slight teredinid attack was detected in ekki and greenheart.
Keywords: Teredinid, shipworm, natural durability, marine borers, lesser-known timber species