Results of investigations on the durability of light weight timber species (Specific gravity below 0.4) i.e., Bombax ceiba and Paraserianthus falcataria in treated and untreated condition conducted at Krishnapatnam harbour (Lat 13o28’ to 13o59’ N; Long: 80o10’ to 80o16’E) along the east coast of India are reported in the paper. Exposure trails were conducted with panels (Size: 30 x 3.8 x 3.8 cm.) treated with CCA (Copper–Chrome–Arsenic) and CCB (Copper-Chrome-Borate) at four retention levels (8, 16, 24, and 32 kg/m3), for a period 3 years from August, 1997 to July, 2000. Control panels of both the species were heavily attacked by shipworms and pholads and rejected in a period of 3 months. On these, panels, shipworms attained maximum growth of 2.3 cm. and pholads 1.4 cm. On these panels. borer species identified were: Martesia striata, M. nairi, Teredo furcifera, T. fulleri, Lyrodus pedicellatus, and Bankia campanellata. Timber panels treated with CCA at lower loadings (8 and 16 kg/3) had greater number of shipworms (>200) than pholads. Shipworms and Pholads attained maximum growth of 2.6 and 1.8 cm respectively. Panels treated with higher loadings (24 and 32 Kg/m3) had more pholads (>150) than shipworms. Pholads and shipworms attained maximum growth of 3.1 and 6.8 cm respectively on these panels. The CCB treated panels of lower loadings also had heavier shipworms (>300) that attained maximum growth of 16 cm, whereas, pholads attained a maximum of 2.2 cm. On higher loadings of CCB treated panels, pholads intensity was observed to be greater and attained a growth of 3.4 cm while shipworm attained 1.9 cm. Overall, shipworm intensity was found to be greater on CCA and CCB panels with lower retentions (8 and 16 Kg/m3), whereas penetration was not deep on higher loadings (24 and 32 Kg/m3). CCA treated panels with lower loadings (8 and 16 Kg/m3) were found to be better than those of lower loadings of CCB. However, at higher loadings (24 and 32 Kg/m3) variations were not significant.

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