In this research, three age groups of Plodia interpunctella (Hübner) eggs (1-, 2- and 3-day-old eggs) were exposed to ultraviolet irradiation (UVC) with 254nm wavelength for 0.5, 1, 1.5, 2, 4, 8, 16, 24, 32 and 40 minutes, under controlled conditions. The effect of UVC-irradiation on reproduction and population growth parameters investigated for eggs irradiated for 0.5, 1 and 1.5 minutes. The percentage of egg hatching decreased with increase in UVC exposure time, while for each exposure time, the older eggs were more sensitive than the younger ones. The results indicated that different exposure times of UVC-irradiation could affect the reproduction and population growth parameters. The highest value of net fertility rates was observed in 1, 2 and 3-day-old eggs which were treated with 0.5 min exposure. Both the intrinsic rate of increase (rm) and the net reproductive rate (R0) decreased with increasing exposure time from 0.5 to 1.5 min while the mean generation time (Tc) and doubling time (DT) increased within this irradiation range. The lowest amount of rm was obtained in 1, 2 and 3-day-old eggs which were treated with 1.5 min exposure time. The results showed that UVC-irradiation is an appropriate technique for controlling P. interpunctella.

Three age groups of eggs of the stored grain pests, Ephestia kuehniella (1, 2, and 3days old) were exposed to ultraviolet irradiation with 254 nm wavelength (UV-C) for different exposure times (0.5-40 min.) under controlled conditions to determine irradiation effect on egg-hatching. The effect of UVC-irradiation on reproduction and population growth parameters was investigated for eggs irradiated for 0.5, 1 and 1.5 minutes. An increase in time of exposure to irradiation caused a gradual decrease in percentage of hatching off eggs in all age groups of eggs. In all treatments, the older eggs were more sensitive to UV-rays than younger ones. The results indicated that different exposure periods of UV-irradiation could affect the reproduction and population growth parameters. The highest value of net fertility rates was observed in 1, 2, and 3-days-old eggs which were treated with 0.5 min exposure time (26.69 ± 4.66, 5.99 ± 0.57 and 1.55 ± 0.16 eggs/female, respectively). Both the intrinsic rate of increase (rm) and the net reproductive rate (R0) decreased with increasing the exposure time from 0.5 to 1.5 min while the mean generation time (Tc) and doubling time (DT) increased within this irradiation range. The lowest amount of rm was determined in 1, and 2 days-old eggs at 1.5 min and in 3-day-old eggs at 1 min exposure times (0.037 ± 0.0025, 0.004 ± 0.0016 and 0.006 ± 0.0008 day-1 , respectively). UVC-irradiation may be used as an alternative approach to control of stored product pests.