Effect of Diatomaceous Earth (DE) Against the Stored Product Beetles, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) under Laboratory Conditions

Abstract

Studies on the control of the saw-toothed grain beetle Oryzaephilus surinamensis with a commercial formulation of the Diatomaceous Earth or diatomite (D); (silicon dioxide made up of fossilised diatoms) were carried out at the Entomology Laboratory at a relative humidity of 50 ± 5%, and ambient temperature of 28 ± 2 °C. Laboratory experiments were applied to assess the efficacy of Diatomaceous Earth dust; silicon dioxide commercially on 2nd-5th instar larvae and adults of O. surinamensis. Three concentrations of Diatomaceous Earth (DE) were weighed (2, 3, and 4 grams), and each concentration was mixed with 100 grams of amber rice grains. Beetles were fed on amber rice grains treated with (DE). The results showed that Diatomaceous Earth (DE) was significantly effective at all tested concentrations after 7 days post-treatment. Nevertheless, susceptibility showed visible significant differences in the mortality level on the last day of the tests between adults, 2nd, 5th instar larvae which were treated with three (DE) concentrations. Adults were least susceptible, while 2nd and 5th instar larvae were most susceptible to DE. All Diatomaceous Earth (DE) was significant and more effective on insect life at a higher concentration of 4 g/100 kg, where the mortality proportion was 100%, 99.50% for 2nd, and 5th instar larvae, respectively, and 97.50% for an adult after 5 days post-treatment. However, all O. surinamensis life stages’ mortality percentages reached 100% after 7 days post-treatment. Consequently, due to the effectiveness of this Diatomaceous Earth on different life stages of O. surinamensis, they could be recommended for the management of this insect. Furthermore, to achieve more effective control over this beetle, formulation of the Diatomaceous Earth (DE); Silicon dioxide, could be used since it appeared to be most effective and consistence in its action against different life stages of the beetle. Lastly, the possibility of using Diatomaceous earth to manage stored-product insects has been debated.