Experiments were conducted to test a portable trench barrier composed of an extruded, UV-retarded, PVC plastic trough, designed to allow Colorado potato beetles, Leptinotarsa decemlineata (Say), to enter and become trapped and killed inside. Tests demonstrated that the portable plastic trenches were effective as barriers to Colorado potato beetles as they walked into tomato, Lycopersicon esculentum Mill., fields from overwintering sites in the spring. In field tests, plots that were protected by portable trench barriers had significantly fewer beetles per tomato plant, and lower levels of defoliation. Tomato yields in plots that were protected by portable trench barriers were similar to yields in plots that were protected by insecticide sprays, and significantly higher than plots where beetles were not controlled.