Ionizing radiation for Quarantine Control of Opogona Sacchari (Lepidoptera: Tineidae)

Authors: Hollingsworth, Robert; Follett, Peter

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2007
Publication Date: 10/1/2007
Citation: Hollingsworth, R.G., Follett, P.A. 2007. Ionizing radiation for Quarantine Control of Opogona Sacchari (Lepidoptera: Tineidae). Journal of Economic Entomology. 100:1519-1524.

Interpretive Summary: An irradiation does of ~150 gray (Gy) of ionising radiation (x-rays) was used to determine which immature stage of banana moth, Opogona sacchari Bojer is most resistant to irradiation. Larvae of several different ages as well as eggs of banana moth were irradiated at a commercial irradiation facility, and then kept in the laboratory for observation. Based on the percentage of insects that successfully developed into adults, we found that early and late pupae were significantly more tolerant than eggs, neonate larvae, or larvae that were one-, two- or three-weeks-old. The irradiation treatment of 150 Gy killed 96, 96, 95, 73, 61, 8, and 9% of eggs, neonates, one-week-old larvae, two-week-old larvae, three-week-old larvae, early pupae and late pupae, in that order. In a second study, an irradiation dose of 250 Gy was tested as a potential sterilising dose for pupae. From 1294 treated pupae that were given the chance to develop into adults, mate and lay eggs, only seven larvae were produced from the eggs that were laid. We conclude that there is evidence that an irradiation dose of 250 Gy is not high enough to sterilise the most tolerant stage (pupae) which can be present in commodities such as fruits and sweet potatoes. Additional research is needed to confirm this result and to determine a sufficient dose that would control banana moth if it were present in a fruit or vegetable commodity being exported.

Technical Abstract: A discriminating dose of 150 gray (Gy) of ionising radiation (x-rays) was used to determine which immature stage of banana moth, Opogona sacchari Bojer, was most tolerant of the treatment. Based on emergence to the adult stage, early and late pupae were the most tolerant stages, and were significantly more tolerant than eggs, neonate larvae, or larvae that were one-, two- or three-weeks-old. Treatment of eggs, neonates, one-week-old larvae, two-week-old larvae, three-week-old larvae, early pupae and late pupae at 150 Gy resulted in a 96, 96, 95, 73, 61, 8, and 9% reduction in adult emergence, respectively. An absored dose of 250 Gy was tested as a potential sterilising dose for pupae. From 1294 treated pupae, seven F1 larvae were produced. We conclude that there is evidence that 250 Gy is insufficient as a sterilising dose for the most tolerant stage commonly occuring in traded commodities. Additional research is needed to confirm this result and determine a sufficient dose that provides quarantine security.