Solvent-based injectable chlorpyrifos (PT(R) 270 Dursban(R), Whitmire Research Laboratories) can travel in a longitudinal direction through structural softwoods, southern yellow pine (Pinus sp.) and Douglas-fir Pseudotsuga menziesii (Mirb.), resulting in a residual treated core approximately 20 cm in length. This treatment can supplement a brush-on or spray-on surface treatment for control of wood-infesting insects.