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Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/8/2008 Publication Date: 6/1/2008 Citation: Follett, P.A. 2008. Effect of irradiation on Mexican leafroller (Lepidoptera: Tortricidae) development and reproduction. J. Econ. Entomol. 101: 710-715. Interpretive Summary: Mexican leafroller has a wide host range including many ornamental plants and tropical fruits such as avocado, guava, macadamia, papaya, pineapple, and rambutan. Mexican leafroller will occasionally travel with imported commodities (e.g. papayas, cut flowers, foliage), and in some countries it is an actionable quarantine pest. For example, Mexican leafroller is a prohibited pest on any commodity exported from the U.S. to Korea, and on papayas and cut foliage exported from the U.S. to New Zealand. Irradiation is a postharvest treatment option for exported commodities to prevent movement of viable Mexican leafrollers. The effects of irradiation on egg, larval, and pupal development, and adult reproduction in Mexican leafroller was examined. Eggs, neonates, early instars, late instars, early pupae and late pupae were irradiated at target doses of 60, 90, 120, or 150 Gy or left untreated as controls. Using regression analysis on mortality data, the dose predicted to prevent egg hatch from the progeny of irradiated late pupae was 120 Gy with a 95% confidence interval of 101-149 Gy. The late pupa is the most radiotolerant stage likely to occur with exported commodities; therefore, a minimum absorbed irradiation dose of 149 Gy (nominally 150 Gy) has potential as a quarantine treatment. Technical Abstract: The effects of irradiation on egg, larval, and pupal development, and adult reproduction in Mexican leafroller, Amorbia emigratella Busck (Lepidoptera: Tortricidae), were examined. Eggs, neonates, early instars, late instars, early pupae and late pupae were irradiated at target doses of 60, 90, 120, or 150 Gy or left untreated as controls and survival to the adult stage was recorded. Tolerance to irradiation increased with increasing age. An irradiation dose of 90 Gy applied to neonates and early instars prevented adult emergence. A dose of 150 Gy was not sufficient to prevent adult emergence in late instars or pupae. The effect of irradiation on sterility was examined in late pupae and adult moths. For progeny produced by insects treated as late pupae, a total of 3 out of 3130 eggs hatched at 90 Gy, 0 out of 2900 eggs hatched at 120 Gy, and 0 out of 1700 eggs hatched at 150 Gy. From regression analysis, the dose predicted to prevent egg hatch from the progeny of irradiated late pupae was 120 Gy with a 95% confidence interval of 101-149 Gy. The late pupa is the most radiotolerant stage likely to occur with exported commodities; therefore, a minimum absorbed irradiation dose of 149 Gy (nominally 150 Gy) has potential as a quarantine treatment. Reciprocal crosses between irradiated and unirradiated moths demonstrated that males were more radiotolerant than females. Irradiation of female moths at a target dose of 90 Gy before pairing and mating with irradiated or unirradiated males resulted in no viable eggs. |
