Development of decay in preservative treated poplar plywood

Poplar is a fast growing species and may become more important in future for both the conversion of agricultural crops and the self supplying policy of the EU. In Flanders, the northern region of Belgium, poplar has become a widely spread species. It provides approximately one third of the wood volume produced while covering merely 10 % of the forest area. Poplar has also very interesting wood properties. Besides a range of specific end products as a light hardwood it is most suitable for the production of plywood. Yet poplar is very vulnerable to the attack of wood destroying organisms, such as wood rotting Basidiomycetes. Therefore poplar plywood should be preserved in all cases where a sufficient service life is at risk. The research described here focuses in particular on the preservative treatment of assembled poplar plywood. Despite poplar plywood being easily treatable, standard retentions for different preservatives do not always result in good protection. To achieve full biological protection of poplar plywood a high loading of preservative is required. The glue-line in poplar plywood does not cause significant problems but it certainly needs consideration. When translating toxic thresholds derived from toxicity testing to practical retention requirements it should be realised that no unique 'multiplication' factors can be established. For special wood products like preservative treated plywood it is important to evaluate the biological durability of the commodity and it should be recommended to introduce a commercially viable quality mark, too. Poplar plywood is considered the most suitable hardwood plywood to be upgraded by means of a preservative treatment. It is easy treatable and its susceptibility to degrade by the white rot fungus Coriolus versicolor is lower than for plywood made of low density tropical wood species.