Development of a mini-block test method for the rapid evaluation of preservative performance against Basidiomycte fungi
J Brown, S Caswell, G R Williams
Screening procedures for new biocides used as wood preservatives can be a time consuming process using conventional Basidiomycete assay procedures. This is due mainly to the long exposure periods required to achieve adequate levels of decay (weight loss) in the test blocks. A number of alternative methods have been developed but most utilise artificial substrates such as filter paper or agar in which inhibition of growth is the main criterion of efficacy assessment. Whilst these methods can provide a comparison of biological activity towards target fungi, they omit the interaction between wood substrate and active ingredient. A further limitation is the inability of these methods to determine preservative performance. A test method has, therefore, been developed based on conventional methodology but using small dimension samples and a reduced exposure period (3 weeks). Results have indicated good test reproducibility with high weight losses of untreated controls. Large numbers of active ingredients or formulations can be rapidly screened using this method and the data can be further used for the estimation of treatment concentrations required for more formal basidiomycete tests such as EN 113.