Fungal decay resistance of 16 tropical wood species embedded with metal screws

Abstract

Decay resistance was assessed for 16 wood species, with metal screws embedded, against five fungal species. Wood species differed significantly in decay resistance. The three most resistant species, Azadirachta indica, Castanopsis tunggurut and Turpinia sphaerocarpa, lost 1.7-4.0% weight (resistance class, R II). Gironniera subaequalis, Lindera polyantha and Hymenaea courbaril were moderately resistant to decay (7.3-9.3% loss, R III) and the remaining species were designated R IV. Screw-embedded specimens lost significantly more weight (14.2 ± 4.0%) than the control (11.0 ± 3.4%). Polyporus sp. and Pycnoporus sanguineus caused significantly more wood weight loss than Schizophyllum commune, which in turn was greater than that for Chaetomium globosum and Dacryopinax spathularia. Screws from wood inoculated with Polyporus sp. lost significantly less weight (3.9 ± 0.7%) than with other fungi. Hymenaea courbaril and A. indica showed the highest and lowest corrosive activity respectively towards screws in the presence of fungi. Screws exposed to C. globosum in culture media lost significantly more weight (10.2%) than with the other fungi. Regression analysis showed that wood weight loss was negatively correlated with wood density of control specimens but not with screw-embedded specimens. Other wood properties including extractives were not found to significantly correlate with wood decay.