Comparison of a Quaternary Ammonium Compound and Copper-Chrome- Arsenate as Wood Preservatives

Sapwood samples of Pinus radiata, Populus robusta, and Eucalyptus regnans were treated with various solution strengths of (a)) alkyl dimethyl benzyl ammonium chloride and (b) copper-chrome-arsenate wood preservative. The treated samples were exposed to attack by pure cultures of basidiomycete and soft-rot fungi. In addition, samples treated with (a) were exposed in unsterile soil. Treatment of all wood samples with a 1.0% a.i. solution strength of the quaternary ammonium compound prevented decay caused by basidiomycetes in all wood species. This corresponds to retentions ranging from 4.4-4.8 kg/m3 (0.15-0.3 lb/cu.ft) in Eucalyptus to 3.2-6.4 kg/m3 (0.2-0.4 lb/cu.ft) in Populus. In contrast, CCA prevented attack by basidiomycetes at retentions of 1.6-2.8 kg/m3 (0.1-0.27 lb/cu.ft) with the exception of Gloeophyllum trabeum in Pinus which required 3.6-4.8 kg/m3 (0.22-0.3 lb/cu.ft). In pure culture tests with soft-rot fungi, 4.8 kg/m3 (0.3 lb/cu.ft) of the quaternary ammonium compound prevented soft-rot in most susceptible hardwood species. Control of soft-rot in both hardwood species was not achieved at retentions of 8.5-9.3 kg/m3 (0.53-0.58 lb/cu.ft) CCA. In the unsterile soil test, undertaken only with the quaternary ammonium compound, soft-rot control was obtained in Pinus and Populus, but some decay still occurred in Eucalyptus at a retention of 9.6 kg/m3 (0.5 lb/cu.ft).

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