Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) which develops inside the grain, is an aggressive pest of stored grains. Here, we evaluated the efficiency of diatomaceous earth (DE), Diatomita CI/325 CX, and dolomite (DOL), Dolomita Dr. Kanyo, against S. zeamais reared on corn under laboratory conditions and observed external alterations on treated insects using scanning electron microscopy (SEM). Insects treated with both DE and DOL were impregnated with particles on the body surface, and they showed 100% mortality after 10 days of exposure. Damages caused by inert dusts may have contributed to dehydration and desiccation, consequently, leading insects to death. Thus, diatomaceous and dolomite were effective against S. zeamais under laboratory conditions.