The larger black flour beetle, Cynaeus angustus (LeConte) (Coleoptera: Tenebrionidae), is an agricultural and home nuisance pest in North America. In the Southern High Plains of Texas, the larger black flour beetle is associated with cotton gin trash, by-products of cotton ginning that are field stored in large piles for economic reasons. Larger black flour beetle overwinter in gin trash piles but may disperse by the millions in summer and autumn, entering houses as far as 2 km away where they cause distress to homeowners. Because >1.2 billion kg of gin trash is produced annually in Texas alone, the potential consequences of the larger black flour beetle are enormous. We conducted a field experiment that evaluated the efficacy of diatomaceous earth (DE) on the abundance of the larger black flour beetle in gin trash. There were no significant differences in numbers of larger black flour beetle among treatments and controls (mean number of adults summed over time: controls = 115.41, layered treatment = 87.60, top and bottom treatment = 96.50, bottom treatment = 115.16). There were sufficient numbers of beetles in treated piles to still pose a potential home nuisance problem, likely because the moisture content of field-stored gin trash is too high for DE to work effectively. Therefore, treating cotton gin trash with diatomaceous earth will probably be unable to prevent home infestations of larger black flour beetle. Location within a gin trash pile and season influenced pest numbers, which has implications for long-term field storage of cotton gin trash.