Efficacy of various wood preservatives on coconut timber exposed under three locations; study 1: stake tests

Results showed that the mean field life of the treated wood specimens depended on S [preservative system], L [preservative retention level] and D [density of wood]. The promising preservative system for cocowood appeared to be the vacuum-pressure using chromated copper arsenate (S1) which was comparable with the modified double diffusion employing copper sulphate, sodium dichromate, and arsenic pentoxide (S2). The performance efficiencies of the treated samples generally improved with increasing preservative retention levels as well as increasing density of wood samples. In ARC graveyard, the best treatment was S1 both for medium and high density wood with mean field lives of 71.8 months at a mean retention levels of 2.61 percent a.i. and 127.1 months at a retention level of 1.72 percent, respectively. In DRC, the superior treatment for high density samples was obtained from S1 with a field life of 86.1 months at a retention of 1.72 percent and for medium density wood from S2 treatment with mean field life of 72.4 months at a retention of 2.06 percent. In ZRC, the most promising treatment for high density samples was S2 which reached an average field life of 104.0 months at a retention level of 1.93 percent while for medium density specimens, the highest field life of 76.6 months was attained employing S2 treatment at a retention level of 1.35 percent. The other treatment combinations involving the modified double diffusion system using copper sulphate with or without sodium dichromate or arsenic pentoxide exhibited significantly inferior field life but they had markedly better field performance than the simple diffusion system employing PQ56, Protek Q and Petachlorophenol. Untreated cocowood stakes (control) installed in these graveyard had field lives ranging from 14.4 to 24.8 months and 7.6 to 12.1 months for high and medium density wood samples, respectively