Abstract
The plant extracts from Zygophyllacae and Euphorbiaceae are well known in the human history for medicinal use but their use to control insect pests is still in preliminary stage. In this study the effects of extracts from Peganum harmala and Ricinus communis on the glutathione S-transferase activity in the fat body as well as midgut tissues of Spodoptera exigua are documented at different exposure times. At the sub lethal concentrations (0.24 and0.49 mg ml(-1)) the highest GST value in fat body tissue (73 nmol CDNB/min/mg protein) was found on the 8(th) day of combined treatment with ricinine and harmaline while in midgut the highest value (69 nmol CDNB/min/mg protein) was noticed on 6(th) day after being treated with ricinine individually. At the lethal concentrations (0.37 and 0.71 mg ml(-1)), the highest GST value (62 nmol CDNB/min/mg protein) was found on the 4(th) day against combined treatment of ricinine and harmaline in fat bodies. In the midgut the highest GST value (59 nmol CDNB/min/mg protein) was observed on the 2(nd) day of combined treatment with ricinine and harmaline. The protein values in all the treatments were significantly lower in treated insects as compared to control.