Insecticidal efficacy of local diatomaceous earth compositions with different particle sizes against stored grain pests

In this study, the efficacy of a mixture of local diatomaceous earth (DE) with different diatomite compositions and particle sizes against stored-grain pests, Sitophilus oryzae L., 1763 (Coleoptera: Curculionidae), Tribolium confusum du Val, 1863 (Coleoptera: Tenebrionidae), and Rhyzopertha dominica (F., 1792) (Coleoptera: Bostrichidae) adults was investigated in 2023 in the Entomology Laboratory of the Department of Plant Protection, Faculty of Agriculture, KSU. In biological tests, 500 and 1000 ppm concentrations (mg DE/kg wheat) of different particle sizes (≤ 20, 20-75, 75-150, and ≥ 150 µm) of DE mixture and original DE (≤ 250 µm) were applied to wheat. The highest mortality rate for all insect species tested at 500 ppm was obtained from DE treatments of ≤20 µm. At 1000 ppm, 100% mortality was observed for T. confusum and S. oryzae in almost all particle size DE-treatments, whereas no local DE treatments resulted in 100% mortality for R. dominica adults. Moreover, the greatest reduction in the number of F1 generation adults for S. oryzae and R. dominica was obtained in the DE treatment of ≤20 µm at 500 and 1000 ppm. In conclusion, local DE mixture treatments with ≤ 20 µm particle size were found to be highly effective in the control of stored-grain pests.