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 ۳۰۰, ۶۰۰, ۱,۰۰۰, ۱,۵۰۰, and ۲,۰۰۰ ppm of the DE deposits. Experiments were conducted at ۲۷±۱°Cand ۵۵±۵% RH in continuous darkness. Mortality of the exposed individuals was counted after ۲, ۵, ۱۰, and ۱۴ 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 ۱۰۰% mortality was recorded on wheat treated with ۶۰۰ ppm of all tested DE deposits after a ۱۰-day exposure. However, for rice, even after ۱۰ days of exposure to ۲۰۰۰ ppm mortality didn’t reach ۱۰۰%. The lowest LC۵۰ value (۳۹ ppm) was obtained in wheat treated with Khorasan DE sample and the highest one (۹۰۸ 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.

Keywords:

Barley storage , Pest management , Rice storage , Stored grain protectant , Wheat storage