Postharvest Irradiation Treatment for Quarantine Control of the Invasive Lobesia botrana (Lepidoptera: Tortricidae).

Irradiation is a postharvest treatment option for exported berries and berry-like fruits to prevent movement of the quarantine pest European grape vine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae). The effects of irradiation on egg, larval, and pupal development in L. botrana were examined. Eggs, neonates, third and fifth instars, and early- and late-stage pupae were irradiated at target doses of 50, 100, 150, or 200 Gy or left untreated as controls in replicated factorial experiments, and survival to the adult stage was recorded. Tolerance to radiation generally increased with increasing age and developmental stage. A dose of 150 Gy prevented adult emergence in eggs and larvae. Pupae were more radiotolerant than larvae, and late-stage pupae were more tolerant than early-stage pupae. In large-scale validation tests, 150 Gy applied to fifth instars in diet prevented adult emergence, but some survival occurred in fifth instars irradiated in table grapes; however, 250 Gy prevented fifth instar survival in grapes. For most commodities, the fifth instar is the most radiotolerant life stage likely to occur with the commodity; a minimum radiation dose of 250 Gy will prevent adult emergence from this stage. For traded commodities such as table grapes that may contain L. botrana pupae, 325 Gy applied to mature female pupae sterilized emerging adults and may provide quarantine security. Radiotolerance in L. botrana is comparable to other tortricids, and the data reported here support a generic dose of 250 Gy for eggs and larvae of this group.