The effect of 10 potato cultivars and clones on the feeding and digestion of Phthorimaea operculella (Zeller) larvae was evaluated using larval nutritional indices and enzymatic activities. Studies were based on nutritional indices from larvae reared at 25 ± 1°C, 65 ± 5% relative humidity, and in complete darkness. The results of nutritional indices showed that conversion efficiency of ingested and digested food in the larvae at the fourth instar was the highest in Savalan cultivar at rates of 22.30 ± 0.39 and 32.87 0 ± 0.69%, respectively, and the lowest were recorded on Morene at rates of 15.83 0 ± 0.35 and 21.99 0 ± 0.58%, respectively. Among the different potato germplasms tested in the study, the highest proteolytic and amylolytic activities of the larvae, at optimal pH were in Morene with records of 8.204 0 ± 0.296 U/mg and 0.071 0 ± 0.0004 mU/mg, respectively; and the lowest were recorded in larvae fed on Savalan at 2.740 0 ± 0.131 U/mg and 0.028 0 ± 0.0001 mU/mg, respectively. It is concluded that Morene was the most unsuitable host for P. operculella.