Antifeedant effect of gamma radiation and Perovskia atriplicifolia essential oil combination against Tribolium castaneum (Coleoptera: Tenebrionidae)

Control of stored-product insect by gamma radiation could be enhanced by other possible techniques such as essential oils as effective alternatives to chemical insecticides. In this study, the efficiency of gamma radiation combined with Perovskia atriplicifolia (Benth) was verified to assess their enhanced antifeedant effect against the Tribolium castaneum (Herbst). Flour disc bioassay was employed to assess the nutritional indices, such as relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion ingested food (ECI) and feeding deterrence index (FDI). The results showed that irradiation, essential oil and combination of both of them significantly reduced RGR, RCR and ECI in treated larvae and adults. As irradiation at ۱۰۰ Gy reduced RGR of the larvae and adults from ۰.۰۸۸۴ and ۰.۰۳۶۶ to ۰.۰۵۹۶ and ۰.۰۳۳۲ mg/mg/day respectively, when combined with doses of P. atriplicifolia essential oil, the reduction reached to ۰.۰۵۱ - ۰.۳۸۸ and ۰.۰۱- ۰.۲۲۴ mg/mg/day respectively. The reduction rates in larvae were even greater when combination of irradiation and EO treatments were used. The results showed a significant increase in the feeding deterrence due to irradiation, essential oil and specially their combination. Therefore, findings led to a conclusion that irradiation can enhance antifeedant activity of essential oils.