Although adult emergence occurred at all irradiation doses, emergence was reduced in
irradiated fruits (Table 2). The 300 Gy treatment did not prevent adult emergence, unlike
previous studies in Hawaii and Australia. This is probably explained by dose variation in
the treatment chamber: the dose uniformity ratio when using the full volume of the chamber
at HRI is 1.6 to 1.8, with the dose distribution skewed toward lower doses (see Follett and
Lower 2000). Therefore, the dose range of the 300 Gy treatment was estimated to be 180–
315 Gy, and many individuals received a radiation dose less than 300 Gy.
Emerging adults from the 100 and 300 Gy treatments were lethargic and short-lived, and
no eggs were laid indicating sterility. Egg laying by untreated control weevils was consistent
but at a relatively low rate compared with weevils in the study by Seo et al. (1974). This
suggests that cage conditions in our studies were not ideal for mating and/or oviposition.
Nonetheless, sterility was achieved in this study with an irradiation dose of 100 Gy (estimated
dose range, 60–105 Gy), as it was in the study by Seo et al. (1974) (Table 2).