Screening wood preservatives: Comparison of the soil block, agar block and agar plate tests
K J Archer, D D Nicholas, T Schultz
Several test procedures have been developed over the years to screen potential biocides for their value as wood preservatives. Each test has inherent advantages and disadvantages. In this paper the relative merits of the soil block, agar block and agar plate tests are compared. Eight commercially available biocides encompassing inorganic and organic systems were tested against four basidiomycete decay fungi. Each biocide was ranked according to its performance in the three tests. The results show that the relative efficacy of the different biocides is dependent on the screening test. Biocides can be separated on the basis of their chemistry. "Fixed" inorganic preservative systems perform better in tests which employ wood as a substrate material. Organic systems perform well in both the agar plate and wood-containing tests. Furthermore, the agar plate technique shows promise for detecting synergism between biocide components. It is concluded that all of these test methods should be considered to efficiently screen biocides for use as wood preservatives.