Evaluating the Stability of Hevea brasiliensis (Rubberwood) as a Control Material in Subterranean Termite Bioassays

Abstract

Subterranean termites are major biological agents causing wood deterioration in tropical regions. Laboratory bioassays commonly use susceptible reference materials as controls to ensure termite feeding activity; however, information on the long-term variability of such materials remains limited. This study evaluated the variability and repeatability of Hevea brasiliensis (rubberwood) as a control material in laboratory tests involving Coptotermes curvignathus. Data from 27 independent trials conducted between 2016 and 2025 were analysed, with five replicates per trial exposed for four weeks using a standardized Forest Research Institute Malaysia in-house method. The mean density ranged from 0.584 to 0.701 g/cm³, while mean weight loss varied from 3.97% to 17.34%. The coefficients of variation for density, weight loss, and visual rating were 6.40%, 39.73%, and 13.11%, respectively. Weak correlations were observed between density and weight loss (r = 0.108), density and visual rating (r = −0.091), and weight loss and visual rating (r = −0.281). The results indicate that variability in feeding damage was primarily influenced by biological differences among termite colonies rather than wood density. Hevea brasiliensis was confirmed as a consistent and suitable control material for laboratory termite bioassays.