Is the effectiveness of diatomaceous earth against stored cereal insects pest beetle pests influenced by the cereal to be protected?

Maize and sorghum are among the most important cereals in the world. They are thus solutions for the fight against food insecurity. Both cereals are unfortunately subject to attack by several insects during storage. These include the maize weevil (Sitophilus zeamais) and the red flour beetle (Tribolium castaneum). Chemical control methods with adverse effects on the environment, applicators, and consumers have long been advocated against these pests. Sustainable management options including the use of Diatomaceous Earth were explored in this study which aimed to comparing the efficacy of a given concentration of Diatomaceous Earth against S. zeamais and T. castaneum on maize and sorghum separately. For this purpose, sorghum and maize were treated with four concentrations of Diatomaceous Earth (1.5, 3, 4.5, and 6 g/kg) and an insecticide-free control for each replicate. For each insect tested, twenty (20) unsexed adults were introduced into each jar. Mortality was measured for each treatment after 24, 48, 96 hours, 7, and 14 days of exposure. Mortalities were corrected for those observed in the control jars and compared for the two cereals (maize and sorghum) using the Mann-Whitney test. Sitophilus zeamais was more sensitive to 0.5 g/kg of Diatomaceous Earth on sorghum than on maize after 24 and 48 h (U = 0.00; p = 0.005). It then showed the same sensitivity regardless of the commodity and the concentration of diatomaceous earth. As for Triboium castaneum, it showed a higher sensitivity on sorghum than on maize. It emerges from this study that the determination of an effective concentration of Diatomaceous Earth should take into account the cereal to be protected and the insect pests to be controlled.