Summary
The termiticidal performance of wood-based composites [medium density fiberboard (MDF),
hardwood plywood, softwood plywood, particleboard and oriented strand board (OSB)] was evaluated
following treatment with a non-ester pyrethroid, silafluofen, using supercritical carbon dioxide
(SC-CO2) as a carrier solvent. Treatment was conducted under nine combinations of temperature
(35°C, 45°C or 55°C) and pressure [7.85 MPa (80 kgf/cm2), 9.81 MPa (100 kgf/cm2) or
11.77 MPa (120 kgf/cm2)]. Treated and untreated samples were individually exposed to the subterranean
termite Coptotermes formosanus Shiraki in the laboratory, and the percent mass loss of the
samples and termite mortality were determined to compare the termiticidal performance among
the wood-based composites and treatment conditions. Silafluofen/SC-CO2 treatment significantly
improved the termite resistance of all of the wood-based composites, although the termiticidal performance
varied with the composite type and treatment conditions. The best performance for
MDF, hardwood plywood, softwood plywood and particleboard was obtained at 35°C-7.85 MPa in
terms of the inhibition of feeding, and gave high termite mortality and energy-conservation,
whereas the best performance for OSB was at 35°C and 9.81 MPa or 11.77 MPa.
