The Effect of X-ray Irradiation on the Fitness and Field Adaptability of the Codling Moth: An Orchard Study in Northeast China

SIMPLE SUMMARY: The codling moth, Cydia pomonella (L.), is an invasive agricultural pest species of pome fruits and walnuts that has developed resistance to many insecticides. Alternative eco-friendly approaches are warranted to reduce the dependence on insecticides for the sustainable management of C. pomonella. The sterile insect technique (SIT) is an autocidal strategy of control that is being trialed in experiments against various pests and that could reduce the risk of the development of insecticide resistance. In our previous study, we found that 366 Gy X-ray irradiation can effectively make the C. pomonella male sterile. In this study, we report on the investigation of the effect of X-ray irradiation on the fitness and adaptability of sterile insects, as well as the first pilot release of sterile male adults of C. pomonella in orchards in China. Results show that 366 Gy of X-ray irradiation significantly shortened the lifespan of the sterile male moths, reduced the mating competitiveness of males, and resulted in males being sterile in the orchards. ABSTRACT: The codling moth, Cydia pomonella (L.), is an invasive agricultural pest of pome fruits and walnuts in China that threatens the apple industry in the Loess Plateau and Bohai Bay; it has developed resistance to many insecticides. Sterile insect technique (SIT) combined with area-wide integrated pest management (AW-IPM) can reduce the risk of resistance to insecticides and effectively control some insect pest species. Our previous laboratory experiment found that irradiation with 366 Gy of X-ray caused the males of the codling moth to become sterile. However, the sterility and adaptability of males after being irradiated with 366 Gy X-ray in the field are still unclear. In this study, we investigated the effect of X-ray irradiation on the fitness of male adults that emerged from pupae irradiated with 366 Gy to explore their adaptability and mating competitiveness, and to examine the effect of releasing sterile male insects in orchards in northeast China on the fruit infestation rate of the Nanguo pear. The results showed that 366 Gy of X-ray irradiation significantly reduced the mating competitiveness of males and the hatching rate of the eggs laid by females pairing with sterile males. Meanwhile, the lifespan of the sterile male moths was significantly shorter than that of the normal ones in the field. A pilot test showed that the release twice of sterile male moths in the orchards had no significant effect on the fruit infestation rate. Our field experiments provide a scientific basis for the further optimization of the SIT technology program for controlling C. pomonella.