A portable, infrared (IR) detector was designed, constructed, and attached to the top of inverted-cone insect traps. The system was used to record and determine the periodicity and total numbers of tobacco budworms and cabbage loopers caught in traps baited with sex lures. Numbers of moths actually caught in traps equipped with IR detector systems during three different field trials were compared with numbers from count records collated from their respective event-marking recorder systems. The IR detector was reliable in adverse weather conditions and was at least 95% efficient. Traps equipped with the IR detector were battery-powered and were operated in remote, typical agronomic open-field environments.