Blended species plywood (white cypress pine and hoop pine): Effect of veneer thickness on susceptibility to attack by the subterranean termite Coptotermes acinaciformis

Abstract

Blended species plywood blocks comprising of 24 different veneer configurations of naturally durable white cypress pine and non-durable hoop pine were exposed to the subterranean termite Coptotermes acinaciformis in a field trial in Australia. Three thicknesses of cypress (1.8, 2.8, and 3.0 mm) and hoop pine (1.0, 1.5, and 3.0 mm) veneer were included. Blocks were assessed for termite damage using a visual damage rating and mass loss measurement. Blocks using all hoop pine veneers received substantial damage; however, blocks that had cypress face and back veneers had improved termite resistance, particularly for the 1.0-mm hoop pine core veneers. When cypress longbands were blended with hoop pine crossbands that created alternating layers, minimal damage was sustained in the hoop pine veneers; however, the damage increased with increasing hoop pine veneer thickness. All cypress veneers received essentially no termite damage, and cypress veneer thickness did not influence the severity of hoop pine veneer damage. The trial indicated that the plywood made with hoop pine core veneers, cypress pine face, and back veneers offered some termite resistance if the hoop pine veneer thickness was kept thin. Alternating cypress and hoop pine further improved the termite resistance.