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The use of wood is limited due to its susceptibility to wood destroying organisms. If wet for long periods, wood will be attacked by fungi and the strength properties will decrease dramatically. To overcome this disadvantage, non-durable wood can be treated with preserving chemicals. When testing durability, it is essential that wood be exposed to all kinds of wood degrading organisms that can be expected in the intended exposure environment.The aim of this study was to evaluate the relevance of exposing test stakes in terrestrial microcosms (TMC) as an alternative to existing test procedures to judge the durability of treated and untreated wood.Small stakes of treated and untreated pine (Pinus sylvestris) sapwood were exposed in TMCs with different soils. Stakes were also exposed to pure cultures of brown and white rot fungi.After exposure, mass losses were determined and stakes from the TMCs were analysed using light microscopy to determine the types of microbial attack.The effect of the preservatives varied depending on the exposure environment.It is concluded that testing the durability of untreated and treated wood with pure cultures of fungi is too limited a test to evaluate total effectiveness. Testing in TMCs represents a good complement to existing procedures and, after further development, an alternative to other laboratory and field tests.1359-5997/98 9 ILILEM

The use of wood preservatives based on copper, chromium and arsenic (CCA) has become restricted in several countries due to environmental concerns. As a consequence, several chromium and arsenic free preservatives based on fungicides, regarded as more environmentally acceptable, have been developed. Most of these preservatives have only been tested in the laboratory against pure cultures of basidiomycetes and their long term effectiveness in practice is in many cases unknown. The effectiveness of six different preservatives, representing different types and combinations of fungicides, against mixed natural populations of micro-organisms, was evaluated during one year in terrestrial microcosms with soils known to provide high activity of different types of wood destroying micro-organisms. Of the fungicides tested, copper compounds provided the best protection against wood destroying micro-organisms. Copper free preservatives provided good protection against pure cultures of brownand white rot fungi, but were ineffective when treated stakes were exposed in unsterile soils.

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