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The contact efficacy of two amorphous silica powders 1 and 2 procured from Imery’s chemicals, Lompoc, CA, USA, were evaluated against the red flour beetle, <i>Tribolium castaneum</i> (Herbst). The efficacy of the silica two powders was evaluated by exposing 10 adults of <i>T. castaneum</i> to twelve different concentrations of silica powder 1 and 2 for 12, 24, 36, and 48 h. Mortality assessments were made after 14 d, and data on adult progeny production were recorded at 42 d. Complete mortality of <i>T. castaneum</i> was observed when adults were exposed for 36 h to concentrations of 1.5 to 5 g/m² of silica powder 1. Conversely, in tests with silica powder 2, complete mortality was only achieved when adults were exposed for 48 h to concentrations ranging from 0.75 to 5 g/m². Silica powder 1 exhibited greater efficacy in inhibiting adult progeny production in <i>T. castaneum</i>, particularly at a concentration of 2.0 g/m² after 24 h exposure. Overall, silica powder 1 displayed superior performance in terms of adult mortality and the suppression of <i>T. castaneum</i> adult progeny production. This advantage can be attributed to the smaller particle size of silica powder 1 when compared to silica powder 2.