The possibility of using radial direction compression strength of wood, rather than mass loss, was evaluated for both a brown-rot fungus (Gloeophyllum trabeum) and white-rot fungus (Trametes versicolor). With untreated pine wafers (5 x 19 x 19 mm³ - l x r x t) exposed to Gloeophyllum trabeum in a soil block test for five days, the compression strength loss was nearly 50% compared to a 5% mass loss. For Trametes versicolor the compression strength loss after 14 days was 25% compared to 0% mass loss. Both CCA and didecyldimethylammonium chloride treated wafers were evaluated against these fungi in the soil block test using both four and six weeks exposure periods. It was found that the toxic threshold values were approximately the same when determined by both compression strength loss and weight loss. However, more definitive toxic threshold values were obtained with compression strength loss. In comparing data from the four and six week exposure times for Gloeophyllum trabeum, it was found that lower toxic threshold values were consistently obtained for the former, regardless of whether compression strength loss or mass loss data was used. Based on the results of this study it appears that compression strength is a much better method for evaluating decay in the soil block test.

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