The purpose of laboratory tests for evaluating efficacy of wood preservatives is usually to establish toxic values against standard strains of wood decay fungi. Exposure conditions are usually chosen as optimal for fungal growth. Toxic values so determined serve as a guide as to expected performance of the preservative in field stake tests or in above ground exposure tests. Test material is selected for uniformity, but exposure conditions, and hence presumably performance, will vary with climate and, if in ground contact, soil type. Service tests measure not only preservative efficacy, but also the suitability of a particular preservative and treatment process to protect particular commodities. Data generated by the NZ Forest Research Institute over the past 40 years on performance of wood preservatives in the above three kinds of test is examined to determine the relevance of each on confident assessment of expected performance of novel preservative systems.

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