The European corn borer, Ostrinia nubilalis (Hübner), is a major pest of US corn, Zea mays L. Genetically-modified corn hybrids (Bt-corn) for the control of O. nubilalis are often part of an IPM-IRM strategy, although development of resistance is problematic. To sustain the use of Bt-corn, the EPA requires expression of a high dose of Bt toxin in the plants and provision of refugia. IRM-strategy details depend on the likelihood that resistant moths emerging from Bt-corn will mate with susceptible moths emerging from refugia or action sites; a significant proportion of mating is presumed to occur within action sites. Understanding this behavior will have implications for IRM because adult dispersal patterns directly affect patterns of mating and gene flow. The objective of this study was to examine the influence of pheromone lure, plant density, and distance from adult-eclosion site on O. nubilalis density among spring wheat, Triticum aestivum L., Siberian foxtail millet, Setaria italica (L.) Beauvois, and oats, Avena sativa (L.). Although feral moths were collected in the action sites in relative abundance, the artificially-marked moths were not found frequently. Our data indicate that a significant proportion of newly-emerged adults were not colonizing the action sites, suggesting that recently eclosed adults leave their natal field and do not settle in the first acceptable action sites encountered.