In Japan, the damages by the subterranean termites (Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe)) are more common. Recently the more attention is paid to the less- or non-chemical methods for termite control. As a non-chemical treatment physical barriers using particles such as gravels were investigated in terms of environmental safety, cost effectiveness, and duration of performance, and the physical barriers using some particles have been practically used in a few countries except Japan. In this study, penetration of termites of C. formosanus into four physical barriers of different particulate materials such as crushed cement-stabilized sludge (Polynite®), palletized-stone powder, and crushed glass, and glass beads as control, were investigated. Layers with particles of Polynite® (1.70 to 2.00mm in diameter), palletized-stone powder (2.00 to 3.35mm), crushed glass (1.00 to 2.80mm), and glass beads (1.00 to 2.80mm) prevented termites from penetrating. The layers of smaller particles were tunneled by termites and the layers of larger particles were passed through. It was found from image analysis of particles that more spherical particles were more efficacious against termite penetration because of their higher compactness. It was also found from roughness measurements of particle surfaces using a stylus instrument that particles of smoother surface were efficacious against both tunneling and penetration of termites. It was recommended to use the particulate materials of smooth surface and spherical shape as a physical barrier.
