Potato tubers were irradiated with different doses of gamma irradiation (50,100 and 200Gy), and fed by the larvae of Phthorimaea operculella (Lepidoptera : Gelechiidae), to measure the effect of larval feeding on some biochemical components of the adult stage. The data indicated that the change in larval diet (tubers) due to irradiation led to some changes in such biochemical components of the adult. Irradiation increased phenolic content and oxidation capacity of potato tubers, while vitamin C was significantly reduced. Vitamin C content of the adult was not significantly changed at most doses. From the nutritional point of view, this means that the decrease in a nutrient in the diet not necessitate  corresponding suppression in the feed insects. Acid and alkaline phosomonoesterases activities and trehalose content of the adult were significantly depressed. Such depression was related to the increased phenolic content of potato tubers after irradiation. This provides an evidence that irradiation of potato tubers could leads to products which might be toxic to insects and able to change in the diet (tubers) component that fed by the larvae. It is interesting to realize that ionizing irradiation inactivate pathogens or directly killed store insect stages, but also could control reinfestation of pest by producing changes in nutrients of potato tubers, and increasing toxic compounds, resulting in abnormalities which could extent to the adult stage and reduce its reproductive capacity.