Fumigant toxicity and sublethal effects of black cumin (Bunium persicum Boiss.), cinnamon (Cinnamomum zeylanicum Blume), and peppermint (Mentha piperita L.) essential oils against the Angoumois grain moth, Sitotroga cerealella Olivier (Lepidoptera: Gelechiidae)

Sitotroga cerealella Olivier, is a species with worldwide distribution, which causes substantial damage to the grain kernels. In the present study, fumigant toxicity (LC50 and LC90) and sublethal effects (LC25) of the essential oils of three medicinal plants including black cumin, cinnamon, and peppermint were evaluated against the eggs and adults of this pest. The chemical constituents of the essential oils were detected by gas chromatography-mass spectrometry. Monoterpenes were the main chemical compounds of the tested essential oils. Fumigant toxicity of peppermint (LC50: 0.5 µl/l air) essential oil against the adults was higher than cinnamon (LC50: 0.94 µl/l air) and black cumin (LC50: 2.42 µl/l air) essential oils. The same trend was also observed against the eggs. The speed of mortality for peppermint (LT50: 8.05 h) and cinnamon (LT50: 9.68 h) essential oils were higher than black cumin (LT50: 14.78 h) essential oil. Results of the experiment of sublethal effects showed that the developmental time of the pest on the essential oils treatments were significantly longer than on control. The lowest fecundity of the pest was observed on peppermint treatment. Furthermore, the tested essential oils significantly reduced the net reproductive rate (R0), intrinsic rate of natural increase (rm), and finite rate of increase (λ) of the pest. The results of this study showed that the tested essential oils, especially the essential oil of peppermint have a suitable potential for decreasing the population of S. cerealella and they can be used in the IPM programs of the pest.