Insecticidal Efficacy of Iranian Diatomaceous Earths on Adults of Oryzaephilus surinamensis

Diatomaceous Earth (DE) is a dust composed of fossilized bodies of unicellular algae used as an insecticide. In this study, the insecticidal potential of four Iranian DE deposits was assessed in adults of Oryzaephilus surinamensis (L.). Three of DE deposits were collected from Maragheh, Mamaghan, and Khorasan Jonoobi mines and Sayan® formulation was obtained from Kimia Sabz Avar Company. The insect adults were exposed on wheat, peeled barley, and rice treated with 300, 600, 1,000, 1,500, and 2,000 ppm of the DE deposits. Experiments were conducted at 27±1°C and 55±5% RH in continuous darkness. Mortality of the exposed individuals was counted after 2, 5, 10, and 14 days of exposure on the treated substrate. Mortality increased with increasing exposure intervals and concentration level. Satisfactory level of protection was observed on wheat grain; as 100% mortality was recorded on wheat treated with 600 ppm of all tested DE deposits after a 10-day exposure. However, for rice, even after 10 days of exposure to 2000 ppm mortality didn’t reach 100%. The lowest LC50 value (39 ppm) was obtained in wheat treated with Khorasan DE sample and the highest one (908 ppm) was achieved in rice treated with Sayan®. The present study suggests that Iranian DEs may be used as potential grain protectants in stored-product pest management programs.