Wheat (Triticum aestivum L.) varietal resistance to the lesser grain borer, Rhyzopertha dominica (F), was evaluated in hard spring and winter wheat produced 2001, 2002 (Bozeman, Conrad, Fort Benton, Havre, Huntley, Kalispell, Moccasin, Sidney, and Winifred, Montana). We tested the hypothesis that seed coat factors, not the endosperm causes feeding resistance to R. dominica and this resistance is a genetic trait(s) not affected by agronomic conditions. Using a rapid, intensive feeding bioassay (frass production), we found no significant difference(ANOVA with SNK means comparison) in resistance to R. dominica, among sound kernels of hard red wheat, comparing all locations and cultural conditions (irrigated versus dryland production). When subsamples of these varieties from the same locations and cultural conditions were first subjected to a heavy infestation of Plodia interpunctella and then to the same age adult R. dominica, damage was significantly greater. Each kernel chosen for this test had been damaged by P. interpunctella larvae to a category five, germ consumed, endosperm fully exposed behind germ. This collaborative damage caused feeding damage by R. dominica to increase two to 7.5 fold (as measured by R. dominica frass production). Protein analysis and hardness were not a factor contributing to the relative hardiness of the wheat.