Effects of X-ray irradiation on sterilization and reproduction of the navel orangeworm, Amyelois transitella

Alternative irradiation technology is needed to avoid the costly security requirements and inherent risks of using ionizing cobalt irradiation for sterile insect technique (SIT) programs worldwide.  X-ray irradiation technology overcomes these security restrictions, but the equipment has been expensive.  We developed a relative inexpensive x-ray system for laboratory experimentation utilizing four low wattage x-ray tubes. The navel orangeworm, the key pest of California tree nuts, pistachios, almonds, and walnuts, was used to test this laboratory scale x-ray irradiation technology.  A range of x-ray irradiation doses or exposure times were presented to three day old male moths that were then allowed to mate with untreated females.  We observed effects of irradiation levels on female fecundity and mating success, and egg sterility/fertility, development, and hatch.  Irradiation effects on reproduction were followed through the F2 generation with significant sterility effects observed at the > 125 grays level, while effects on reproductive success and efficiency were found at > 75 grays level.  These results support navel orangeworm as a potential candidate for SIT and the utility of x-ray irradiation.