Lahar aggregates from Mt. Pinatubo consisting of uniform or mixed particles were tested as physical barriers to prevent tunneling and penetration ofNasutitermes luzonicus, Macrotermes gilvus and Microcerotermes losbanosensis. Uniform particle diameter in the range of 1.18 - 1.40 mm to 2.0 - 2.36 mm prevented N. luzonicus and M. losbanosensis or 1.70 - 2.00 mm to 2.00 - 2.36 mm for M. gilvus from penetrating the lahar barrier. When several particle sizes in the diameter range 1.18 - 2.36 mm or 1.70 - 2.36 mm were uniformly mixed, the resultant barrier prevented penetration of N. luzonicus or M. losbanosensis and M. gilvus, respectively. Repellency tests showed that lahar particles were neither repellent nor toxic to N. luzonicus, M. gilvus and M. losbanosensis. Field evaluations using mixed particle sizes 1.18 - 2.36 mm and 1.70 - 2.36 mm performed very well in preventing tunneling of field colonies ofM. losbanosensis and M. gilvus, respectively.