Considering the adverse effects of storage insect pests and their resistance to chemical insecticides, identifying safe, cost-effective, and durable methods to control and reduce storage pest-induced damage appears essential. Utilizing diatomaceous earth is one alternative to chemical pesticides for controlling stored-product insect pests. This study evaluated the insecticidal activity of diatomaceous earth at a concentration of 0.2 mg/cm2 against two stored-products insect pests, Rhyzopertha dominica F. and Tribolium confusum Jacqulin Duval, on concrete, mosaic, and galvanized steel surfaces. To this end, the surfaces were treated with different diatomaceous earth formulations, including a commercial formulation, SilicoSec®, an Iranian formulation, Dryasil, Dryasil + 0.05% Mentha longifolia L. extract, and talcum powder + 0.05% M. longifolia extract. Mortality was measured 1, 3, 5, and 7 days after treatment. The experiment was conducted at 27 ± 1 °C, 60 ± 5% relative humidity, and dark conditions. The experiments were performed in nine replications (10 adults in each replication). The mortality percentage of R. dominica 7 days after treatment with Silicosec®, Dryasil alone, Dryasil + 0.05% M. longifolia extract, and talcum powder + 0.05% M. longifolia extract on galvanized steel were 43.33, 54.44, 33.33, and 25.55%, respectively. The results indicated that the mortality percentage of T. confusum on galvanized steel was 35.55, 45.55, 26.66, and 23.33%, respectively. The mortality of T. confusum was lower than that of R. dominica adults. Results indicated that the insecticidal effect of diatomaceous earth increased over time. Diatomaceous earth alone had a more significant insecticidal effect than combining them with M. longifolia extract. The highest percentage of mortality in all treatments was found on the galvanized steel, mosaic, followed by concrete surfaces, respectively. Therefore, Dryasil formulation can be used to control stored-products pests in grain silos, although its insecticidal efficacy varies based on surface type.