This paper is a continuation of previous work reported in IRG/WP 96-20089 by Molnar et al. (1996) in which Lap-joints, made from Southern yellow pine and treated with ACQ, DDAC or propiconazole were sampled over 12 months exposure at Hilo, Hawaii. 18 and 24 month samplings have since taken place and are reported here. TnBTO treated Lap-joints made of scots pine which were exposed later as a standard treatment (ENV 12037: 1996) have now been sampled up to 12 months. The observations and conclusions reached after the recent 18 and 24 month exposure period have, in the majority of cases, been consistent with those made from the earlier samplings. Visual assessments according to ENV 12037 indicated that only the untreated joints were starting to fail at 24 months. Visual assessment also indicated that ACQ treatments performed well but DDAC samples less so. It was observed from detailed sampling that the discoloration of a sample may give a misleading rating, many joints appearing poor but being internally sound. Differences in the pattern of colonisation of the Lap-joints after 24 months exposure were now more clearly associated with different treatments. Bacteria and moulds were common throughout the 24 months, although moulds were inhibited in TnBTO treated samples. Bacteria and yeasts were abundant in propiconazole and DDAC treated samples. Soft-rots were uncommon, with the exception of Phialophora sp. which occurred frequently with ACQ, and rarely in propiconazole treatments. Aureobasidium pullulans was a common stainer but was inhibited by propiconazole and ACQ treatments. A. pullulans was dominant on TnBTO treated Lap-joints. A limited number of Basidiomycetes were isolated, especially from the untreated samples, and these included Phellinus sp., Postia placenta and Gloeophyllum sp.

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