Pinus radiata test stakes were treated with 10 kg/m3 of CCA plus 4 lower retentions in a geometric series of 1.5. Fagus sylvatica was treated with 15 kg/m3 and 2 lower retentions. Both timber species were also treated with equivalent retentions of various new generation preservatives (P. radiata was also treated with creosote). Whilst these stakes were exposed at 11 sites in New Zealand (NZ) and 2 in Queensland Australia, this paper reports only data from a single NZ site where preservative and timber species effects on decay type were particularly pronounced. Of particular interest was the finding that copper-azole and copper-quat. treated pine was less susceptible to soft rot attack but more susceptible to attack from tunnelling bacteria, compared to CCA treated wood. Beech was not attacked by tunnelling bacteria but was attacked by an unusual type of fungal cavitation/erosion. These, and other preservative and timber species effects on decay type are discussed.

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