Toxicity of plant essential oils three on physiological activity of fourth instar larvae of Sitotroga cerealella (Oliver)

Angoumois grain moth, Sitotroga cerealella, is one of the most critical storage pests with a wide range from the hosts in Iran and worldwide. Excessive consumption of chemical insecticides leads to developing the resistance to chemical insecticides, environmental pollution, and the emergence of new pests. Therefore, we have decided to reduce the risk of the environment in pest’s control via plant essential oils.

In the current study, to examine the environment- friendly pesticides, effects of three plant essential oils from the families Mentha longifolia L., Thymus daenensis Celak (Lamiaceae), and Artemisia aucheri Boiss (Asteraceae) compared to dichlorvos (DDVP®,as a positive control) an organophosphate insecticide were studied. Antioxidant enzymes, including: superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation marker on the fourth instar larvae of S. cerealella after 24 hours were examined. The essential oils were prepared using the water distillation method. Essential oils were used in five concentrations and three replications. The concentration was selected based on the primary experiment for each essential oil. Insects were exposed to fumigant toxicity of the essential oils and insecticide in laboratory conditions (25±1 °C, 70±5% in 12 hr light/12 hr dark).

The results showed that LC50 for the essential oils of M. longifolia, T. daenensis, and A. aucheri were recorded 0.04, 0.68 and 6.47 μL/Lair, respectively. The highest mortality rate increased with high concentrations (0.09, 3 and 9 μL/Lair) of M. longifolia, T. daenensis and A. aucheri essential oil were 84, 80.67, and 77.33 %, respectively after 24h. Enzymatic activity increased with essential oil high concentrations. Data indicated a significant increase in the activity of catalase, superoxide dismutase enzymes and the concentration of malondialdehyde as peroxidation lipid indicator in treated larvae with essential oils of M. longifolia, T. daenensis and A. aucheri compared with the untreated (negative control), and DDVP® (positive control) on treated 4th instar larvae of S. cerealella after 24h. 

 Conclusion

It seems that different essential oils of M. longifolia, T. daenensis and A. aucheri with the effect on the enzymatic activities of antioxidants, including catalase, superoxide dismutase enzymes and malondialdehyde as lipid peroxidation indicator of the fourth instar larvae of S. cerealella via the disruption of physiological processes and survival. Regarding the existence of different aromatic plants in Iran, we can use the species with higher toxicity that would be more economical to produce the botanical insecticides and use in the integrated pest management programs for this pest control.