Toxicity and Physiological Effects of Essential Oil from Agastache foeniculum (Pursh) Kuntze Against Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) Larvae.

Aims: It is acknowledged that many essential oils isolated from various plants can exert toxic activity against insect species. In the present study, the essential oil from aerial parts of Agastache foeniculum (Pursh) Kuntze (Lamiaceae) evaluated for its larvicidal and physiological effects against the larvae of Tribolium castaneum Herbst. Place and Duration of Study: Place – Department of plant protection, Faculty of agriculture, Guilan university, Rasht, Iran. Duration – May, 2012 to January, 2013. Methodology: The essential oil was isolated from aerial parts of A. foeniculum by hydrodistillation method with a Clevengertype apparatus. In Larvicidal bioassay, five concentrations of the essential oil were prepared with acetone as solvent. Control samples were treated only with pure acetone. Ten same-aged instars were randomly selected, placed with treated diets and kept at 27 ± 2ºC and 60 ± 5% RH. The experiment was repeated four times and insect mortalities were recorded after 24 h. The effects of essential oil on total carbohydrate, lipid and protein contents on the surviving larvae were assessed. Also, the responses of general esterase and glutathione S-transferase as two detoxifying enzymes to essential oil were investigated. Results: A. foeniculum essential oil caused high mortality and the mortality was dose dependent i.e. with increasing of essential oil concentrations more mortality achieved. Furthermore, study on the effect of essential oil on total carbohydrate, lipid and protein contents demonstrated that all of them were decreased with increasing of concentrations. When A. foeniculum essential oil was applied, inhibition of esterase and glutathione Stransferase activities was observed. Conclusion: It has been found that the essential oil of A. foeniculum may produce a great range of biological effects on T. castaneum larvae and can be a potent candidate for such insect pest management.