Effect of gamma irradi&tion of male full grown pupae of P242.pera littoralis (Boisd..) in the parental generation on the susceptability of the larvae produced in Fi generation to extracts of two plant species; namely; Tafia (Nereum oleander) and Nabk (Flacourtia indica) were determined. Larval mortality depended on radiation dosages, type of plant extracts and solvents. Radiation dosages alone did not apparently affect Fi larvae, but joint treatment with irra— diation plus plant extracts effectively suppressed larval development with 2.5 or more times in comparison with irra diation and plant extracts separately. The toxicity of plant extracts to Fi larvae (whose male pupae had been irradiated) was more than its toxicity to the larvae produced from unir— radiated parents.