Larvae of Agrotis segetum were collected from potato fields. The larvae were kept in petri dishes in an incubator, under controlled conditions of temperature (27 +- 0.5 /sup 0/C) and an alternate photoperiod (12L : 12 D). The larvae were fed on fresh potato leaves. Fifth instar larvae from laboratory-reared insects (after third generation) were gamma irradiated at different doses of 0, 50, 100 and 150 Gy. For each dose 20 larvae were irradiated and daily observations were made on postirradiation mortality.
Similarly 5 day old pupae from laboratory-reared insects were irradiated at doses of 0, 50, 75, 100 and 150 Gy. For each dose 20 pupae were irradiated and adults which emerged out were mated with normal females to see the egg laying and their hatchability percentage. The mortality as well as the number of eggs laid and the hatchability percentage were dose-dependent. A sterility dose is proposed between 50-75 Gy in 5 day old pupae.