Inherited sterility for area-wide control of corn stem borer, Sesamia cretica (Led.)

Full text: The corn stem borer, Sesamia cretica (Led.) feeds almost exclusively on corn, Zea maiz and causes economic losses. The corn stem borer is often the key pest of corn in all corn growing governorates in the middle of Iraq. Various control tactics were proposed to reduce damages inflicted by this pest, such as cultural practices, chemical and biopesticides and resistant varieties. As a further step in consideration of an area-wide integrated control programme for corn stem borer, the present investigation shows the results of the induction of inherited sterility in F1 and F2 individuals. Male pupae of 8-10 days old were irradiated with 200, 250 and 300 Gray. All possible combinations of mating types were done for F1 and F2 adults. The following parameters were recorded: Adult longevity, percent mated females, female fecundity and egg hatchability. The results indicated the following: 1. Irradiation of male pupae did not affect significantly spermatophore transfer to the females, and this was noticed also in F1 and F2 adults. 2. There were no significant differences in average male longevity at parental, 1st and 2nd generations. 3. At all doses used, there was a noticeable reduction in fecondity at all mating types of 1st and 2nd generations. 4. Significant reduction in eggs hatching at all mating types of 1st and 2nd generations. 5. It was clear that 1st generation adults were more sterile than their parents at all irradiation levels. 6. The level of induced sterility in 1st generation females was higher than that of the males. 7. The males and females of the 2nd generation were less sterile than that of the 1st generation, but still more than that of the parent. 8. The females of the 2nd generation were less sterile than males of the same generation. It was documented that the success of any sterile insect release programme depends on a number of irradiated individuals that mate normally with native ones. The results indicated that mating percentage in all types of mating in both generations were not different with that of the control. The normal level of fecundity at any mating type and the high level of sterility in the F1 individuals, which is considered a typical phenomenon of Lepidopteran inherited sterility, contributes positively to the area-wide integrated control programme of corn stem borer in Iraq. (author)