The potential for pheromone-based mating disruption (MD) ofEphestia kuehniella (Walker) andPlodia interpunctella (Hübner) (Lepidoptera: Pyralidae) was investigated in two flour mills and a pet food distributor. Plastic sachets emitting 2–3 mg per d (Z,E)-9,12-tetradecadienyl acetate, the major pheromone component of both moth species, were used as MD dispensers, which were applied in grid systems resulting in one dispenser per 100 m³ of air volume. Pheromone traps with sticky inserts were used to monitor moth population fluctuations. To monitor pheromone levels in the air before, during, and after the treatment, electroantennographic (EAG) measurements were performed using a portable device. All localities showed decreased trap catches after application of MD. In two localities with low initial population densities, trap catches were reduced immediately after application of MD and remained very low, even several months after the MD treatment was terminated. In contrast, in a locality with a higher initial population density the reduction in trap catches was slower, and trap catches increased again soon after the termination of the MD treatment. Electrophysiological data showed not only increased aerial levels of pheromone during the treatment period but also levels that were higher than during pretreatment, even 12 mo after removal of MD dispensers. The localities had good ventilation, and the memory effect observed indicates that the pheromone adhered to surfaces that subsequently functioned as secondary dispensers. Customer complaints registered by one of the mills were 49% less in 2004, after 2 yr of MD compared with 2002, the year before the treatments began.