Efficacy and characterization of synthesized metal oxide nanoparticles and diatomaceous earth on stored product insect control

Abstract

Nanotechnology has emerged as the most promising novel approach for stored product insect control. In this study, laboratory experiments were applied to assess the efficacy of three mixtures of powdered samples prepared by mixing diatomaceous earth (DE) with zinc oxide in different ratios (90%:10%, 80%:20% and 70%:30%) on adults of Tribolium castaneum, Rhyzopertha dominica, and Oryzaephilus surinamensis, as well as the effect of these mixtures on emerged adults in the first generation. Also, the germination percentages of wheat seeds treated with LC₅₀ values in all tested materials was considered. ZnO nanoparticles was prepared by precipitation method. XRD results showed that DE to zinc oxide ratios were close to the experimental values. FE-SEM images of the three mixtures confirmed the immobilization of ZnO on diatom where the surface is regularly coated with smaller ZnO nanoparticles. All formulations demonstrated higher toxicity after 14 days of exposure than DE alone. Notably, 30% ZnO showed a substantial increase in toxicity, with relative potencies of 6.82, 6.05, and 7.08-fold compared with DE alone against T. castaneum, R. dominica, and O. surinamensis respectively. Complete progeny suppression was achieved at 1500 and 2000 ppm for T. castaneum and R. dominica at 20% and 30% ZnO. At 300 ppm or more, O. surinamensis attained 30% ZnO, which totally reduced progeny formation. 30% ZnO was the most effective formulation for maintaining wheat germination, with 95% germination after both 7 and 14 days, though the difference from the control (100%) was not significant. Combining DE with zinc oxide significantly improves germination in wheat seeds. The highest concentration of ZnO was the most effective against all tested insect species.