Technical Abstract: The Mexican rice borer, Eoreuma loftini (Dyar), is the key pest of sugarcane, Saccharum spp., in Texas; it can attack a number of grassy crop and noncrop host plants, and has spread into Louisiana. Through small plot, commercial field, and pheromone trap experiments, this study demonstrates that the pest utilizes corn more than sugarcane and sorghum, but when corn is harvested in late summer, injury to nearby sugarcane strongly increases during the next 2 mo to harvest. Corn was also more infested than sugarcane and sorghum in commercial fields, and regardless of whether sampling occurred on field edges or farther into field interiors. Differences in numbers of infested stalks and in numbers of larval entry holes between field edges and interiors were not detected. We found that Mexican rice borer infestation of corn can cause loss of ears, and lodging, shattering, and complete destruction of stalks. The larger quantities of adult Mexican rice borers captured in pheromone-based traps placed at corn field edges further indicates that corn is preferred to sugarcane and sorghum. The basis for the pest’s attraction to corn and implications to potential range expansion to other United States sugarcane growing regions are discussed.