Persistence and Efficacy of Four Iranian Diatomaceous Earths Against Three Stored Grains Beetles

Persistence and efficacy of four Iranian diatomaceous earth formulations was assessed against Sitophilus oryzae (L.), Tribolium castaneum (Herbst) and Tribolium confusum Jacquelin du Val. on barley, rice and wheat. Three diatomaceous earth samples were collected from Maragheh, Mamaghan, and Khorasan Jonoobi mines and Sayan® formulation was obtained from Kimia Sabz Avar Company. Mortality of the exposed individuals was recorded after 2, 5, 10 and 14 days of exposure. The mortality of all tested species was higher on wheat followed by barley. The insect mortality increased with increasing concentration level. In most cases, Khorasan was the most effective diatomaceous earth deposit. LC50 values of Khorasan deposit was 155.3, 201.5 and 293.7 ppm for S. oryzae,T. castaneum and T. confusum, respectively when exposed for 7 days on treated wheat. Adults of S. oryzae were the most susceptible species to diatomaceous earths. Subsequently, the persistence of diatomaceous earths was assessed after 1, 2, 3, 4, 6 and 8 months of storage. Mortality of all the tested species was high in first four months of storage but decreased rapidly overtime. © 2016, The National Academy of Sciences, India.