Heartwood of copper-chrome-arsenic (CCA) treated kempas (Koompassia malaccensis), tualang (Koompassia excelsa) and keruing (Dipterocarpus spec.) was found to be susceptible to soft rot in recent pole surveys. Standardized heartwood blocks were impregnated with 0 to 6.3% (w/v) CCA and challenged to decay for twelve weeks by a mixed inocula of Chaetomium globosum, Glenospora graphii, Humicula grisea, Petriella setifera and Trichurus spiralis in containerized vermiculite-burial decay system. Fixation of CCA in wood immediately following impregnation took place by steaming (110°C, 1 h) or by slow drying (4 w), and half of both were leached (CEN 84). A similar burial test using soil was included for comparison. Average% mass loss (ML) in treated keruing was generally <3% with no clear differentiation among CAA levels, methods of fixation with or without leaching and decay methods. A relatively gradual-to-abrupt increase in resistance with higher levels of CCA was found for kempas and tualang, where average ML of the untreated samples for each combination of fixation/leaching was between 5 and 9% (inoculated vermiculite) or 3% (unsterile soil) with negligible decay at concentrations of about 2% CCA and above. The suitability of such soft rot tests with treated heartwood is discussed.

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