Insecticidal efficacy of diatomaceous earth against the larger grain borer, Prostephanus truncatus (Horn) on stored maize

Abstract Laboratory studies were conducted to evaluate the insecticidal effect of diatomaceous earth (DE) against adults of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) in maize. Four concentrations of diatomaceous earth (0, 1000, 2000, and 3000 ppm; n = 9) were tested, and adult mortality was assessed after 3, 7, 14, and 21 days of exposure. After the final mortality counts, dead and live parental adults were removed and progeny production (number of emerged F1 adults) was measured following an additional incubation period of 50 days. Adult mortality was strongly influenced by diatomaceous earth concentration, with higher concentrations resulting in better insecticidal efficacy. However, the effect of exposure duration was less pronounced regardless of the diatomaceous earth concentration, with adult mortality remaining below 47% even after 21 days of exposure to 3000 ppm of diatomaceous earth. Progeny production was also significantly reduced at higher concentrations, indicating that diatomaceous earth can provide both direct and residual control of P. truncatus . The results of the present study demonstrate that diatomaceous earth can be effectively used as a grain protectant at high concentrations in stored maize, although further evaluation under commercial storage conditions is necessary to optimize its application.