The effect of CaCl2 on growth rate, wood decay and oxalic acid accumulation in Serpula lacrymans and related brown-rot fungi

Abstract The dry rot fungus, Serpula lacrymans , is one of the most destructive copper-tolerant fungi causing timber decay in buildings in temperate regions. Calcium and oxalic acid have been shown to play important roles in the mechanism of wood decay. The effect of calcium on growth and decay was evaluated for 12 strains of S. lacrymans and compared to five brown-rot fungi. This was done by treating copper citrate (CC)-treated Southern yellow pine (SYP) wood with a CaCl 2 solution and estimating the decay rate and amount of soluble oxalic acid in an ASTM soil block test. Decay by S. lacrymans was found to be significantly inhibited by treatment with CaCl 2 in the presence of copper. In addition, calcium showed no effect on two strains of S. lacrymans and one Serpula himantioides strain in non-copper-treated SYP wood blocks. The growth rate of S. lacrymans was not affected on malt extract agar containing CaCl 2 . In summary, a marked decrease was observed in the decay capacity of S. lacrymans in pine treated with CC+CaCl 2 . The amount of soluble oxalic acid was measured in CC-treated blocks and blocks also treated with CaCl 2 . Of the comparative brown-rot fungi, both Antrodia vaillantii (TFFH 294) and Postia placenta (Mad 698) displayed notable wood decay despite CaCl 2 treatment, while the remaining strains were inhibited.