Gamma Irradiation of Codling Moth (Lepidoptera: Tortricidae) Eggs as a Quarantine Treatment

Abstract

Exposure of codling moth, Cydia pomonella (L.), eggs to gamma irradiation at a rate of 14.3-14.5 Gy/min showed that younger eggs were more radiosensitive than older eggs. Eggs that were 0-1 d old hatched when treated at 50 Gy, but not at 100 Gy. Eggs that were 3-4 d old hatched when treated at 200 Gy, but not at 400 Gy. Radiation injury to eggs was also measured by the stage in which mortality occurred in embryonated and unhatched eggs. Most of the 0- to 1-d-old eggs died in the preblackhead stage at all doses. Most of the 3- to 4-d-old eggs died in the blackhead stage. The minimum dose that prevented hatch of 5- to 6-d-old eggs (the most radioresistant egg stage) was 1,400 Gy. Application of doses sublethal to 5- to 6-d-old eggs showed that neonate larvae apparently did not develop beyond the first instar at 400 Gy. No pupation occurred at 200 Gy, and only males developed to pupae at 100 Gy. None of these emerged as adults. At 50 Gy, reduced numbers developed to adults, and single-pair reciprocal crosses of moths from treated and untreated eggs resulted in no mating based on absence of spermatophores. Gamma irradiation is a potential quarantine h’eatment for disinfesting fruit of codling moth eggs.