A detailed microscopical examination has been carried out on samples taken from CCA-treated pine posts exposed in horticultural soils. The following decay types were observed: white rot, brown rot, soft rot, tunnelling bacteria, cavitation bacteria, and bacterial erosion. The occurrence and importance of the various decay types between different regions, and plots within a specific region, varied considerably. Soft rot was the most common type of degrade observed and it was also considered to be the most important decay type in terms of reducing the service life of the posts. Tunnelling bacteria were found to have caused extensive degrade in several properties. Cavitation bacteria were of considerable significance in one property. The other decay forms were regarded as being less important. Their contribution to the degrade in the outer parts of the posts was, however, quite substantial.

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