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Natural resistance of twenty-five timber species to marine borer attack in Goa waters (India)
1992 - IRG/WP 92-4178
Natural durability of 25 species of Indian timbers has been discussed, based on data collected from test panels exposed in Goa waters (west coast of India. for a period of 7 months. All the timber species, except Cleistanthus collinus, were heavily destroyed within 7 months on account of the combined attack by Martesia striata (Linnaeus) and Lyrodus pedicellatus (Quatrefages). Cleistanthus collinus, though harboured numerous Martesia striata, did not suffer internal damage (only less then 2%), as the growth of borers was very much restricted. This is attributed to the presence of certain lignan-lactone glycosides like Cleistathin-C and Cleistathin-D in the wood. Similary, species like Wrightia tomentosa and Lannea coromandelica were destroyed exclusively by Martesia striata, indicating the presence of chemicals poisonous to shipworms. The results have been compared and discussed with those reported by previous workers.
L N Santhakumaran, G Srimannarayana, K Nagaiah
Cleistanthus collinus (Roxb.) Benth. ex Hook. f. and Wrightia tinctoria (Roxb.) R. Br. -- two timbers with promising durability under marine conditions
2005 - IRG/WP 05-10552
During the course of natural durability studies on indigenous timber at Visakhapatnam harbour, two species, namely, Cleistanthus collinus (Karada) and Wrightia tinctoria (Dudhi) were found to resist marine borer attack for reasonably longer periods. The panels of C. collinus completely resisted borer attack for 9 months but became susceptible to teredinid attack thereafter. The teredinids gradually attacked the panels in increasing numbers and by the end of 24 months of exposure trials, the apparent destruction caused by the borers reached >50%. However, on splitting open the panels, the internal destruction was found to be only 8% as majority of teredinids could not penetrate deep into wood, leaving only superficial pits. The panels of W. tinctoria completely resisted borer attack only for 3 months unlike C. collinus. Subsequently, this species became susceptible to pholadid attack but continued to resist teredinid attack for 12 months. The wood borer attack, especially of pholadids followed by teredinids gradually increased and by the end of 30 months, the apparent destruction reached >50%. However, on inspecting the split open panels, the internal destruction was observed to be 60%.
M V Rao, M Balaji, V Kuppusamy, K S Rao