Effectiveness of diatomaceous earth formulations against seven stored-product insect species on wheat

Laboratory bioassays were conducted to determine the effectiveness of three diatomaceous earth (DE) formulations against seven stored-product insect species on hard red winter wheat. Adults of the red flour beetle, Tribolium castaneum (Herbst); lesser grain borer, Rhyzopertha dominica (F); sawtoothed grain beetle, Oryzaephilus surinamensis (L.); rice weevil, Sitophilus oryzae (L.); maize weevil, Sitophilus zeamais Motschulsky; granary weevil, Sitophilus granarius (L.); and eggs of the Indian meal moth, Plodia interpunctella (Hübner), were exposed to wheat treated with dry Dryacide^®, a slurry prepared by dissolving dry Dryacide^® in water, or liquid DE at 1 g/kg. Adult mortality was assessed after 7 and 14 d and progeny production after 42 d. In general, the mortality of each species increased with increasing exposure time. Dry Dryacide^® was effective against all the Sitophilus spp., O. surinamensis and P. interpunctella, but not against T. castaneum and R. dominica with overall mortality being ≤ 85%. The efficacy of slurry was lower than that of dry Dryacide^®. Except for O. surinamensis, the liquid DE performed poorly against all species.