Insecticidal activity of two amorphous silica powders applied to concrete surfaces against the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

Abstract

The increased demand for residue-free food grains has led to exploring diatomaceous earth formulations as potential alternatives to synthetic insecticides. In the present study, we evaluated the efficacy of two amorphous silica powders 1 and 2 with different elemental composition, particle diameter, and shape characteristics against the confused flour beetle, Tribolium confusum Jacquelin du Val. The insecticidal activity of the two silica powders was determined by exposing T. confusum adults to silica powder treated concrete arenas at different application rates (0, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 g/m2) for 12, 24, 36, and 48 h. Mortality assessments were made after 14 d, and adult progeny counts were made at 42 d. Silica powder 2 demonstrated greater efficacy and produced 100% adult mortality and completely inhibited adult progeny production when adults were exposed for 24 h to an application rate of 4.0 g/m2. Complete mortality and complete suppression of adult progeny production was noticed after 36 h exposure to 3.5 g/m2 of silica powder 1. Exposure of T. confusum adults to 6 g/m2 of silica powder 1 and 4 g/m2 of silica powder 2 gave complete mortality after 24 and 20 h, respectively. No adult progeny production was observed when adults were exposed for 24 h to 6 g/m2 and 4 g/m2 of silica powder 1 and silica powder 2, respectively. These findings suggest that the two silica powders hold promise for managing T. confusum, particularly in treating empty bin floors before storing new grains.