When fourth instar larvae of Spodoptera littoralis or when F₁ fourth instar larvae (resulted from irradiated parent male pupae) of Spodoptera littoralis treated with four concentrations of jatropha oil (2.5, 5, 7.5 and 10%) the %mortality increased with the increase of both concentration and the time of exposure to the oil. effect of Lc₅₀ of jatropha oil on acetylcholinesterase activity and lactate dehydrogenase of normal and F1 larvae (resulted from irradiated parent male pupae), acetylcholinesterase activity decreased non-significantly in S. littoralis larvae treated with jatropha oil compared to normal larvae the same results obtained in F1 S. littoralis larvae where acetylcholinesterase activity decreased in  F1 irradiated  S. littoralis larvae treated with jatropha oil compared to untreated F1irradiated larvae. while lactate dehydrogenase activity increased significantly in S. littoralis larvae treated with jatropha oil compared with normal larvae. The same results were obtained in F1 S. littoralis larvae where lactate dehydrogenase activity increased in F1 irradiated S. littoralis larvae and treated with jatropha oil compared to untreated F1 irradiated larvae. Consequently, it can be concluded that a combination of jatropha oil and gamma rays could serve as an eco-friendly control program for cotton leafworms.