Feeding deterrency of two medicinal plant extracts on Tribolium castaneum (Coleoptera: Tenebrionidae)

The aqueous and hydroalcoholic extracts from aerial parts of Berberis thunbergii L. and Alhagi maurorum Fisch. were tested against the red flour beetle, Tribolium castaneum (Herbst), for antifeedant activity, which was measured by nutritional indices parameters such as relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI) and feeding deterrence index (FDI). Treatments were evaluated by the method of flour disc bioassay in the dark, at 27 ± 1 °C and 60 ± 5% RH. Aliquots of 10 μl of several concentrations from each extract (0.25-2.0%) and controls (solvents) were spread evenly on the flour discs. After evaporation of the solvent, 10 adult insects were introduced into each treatment. After 72 h, nutritional indices were calculated. Results indicated that nutritional indices varied significantly as extract concentrations increased. The difference between extracts and treatments was significant (P < 0.05). In this study, A. maurorum decreased RGR, RCR and ECI significantly more than those of B. thunbergii extract. In addition, hydroalcoholic extracts decreased RGR, RCR and ECI significantly more than those of aqueous extracts. Both plant extracts increased FDI as the extract concentrations were increased, showing high feeding deterrence activity against T. castaneum. Generally, antifeedant activity of A. maurorum was greater than that of B. thunbergii and hydroalcoholic extract was more effective than aqueous extract.