Feasibility of using X-ray to irradiate adult for control of the oriental fruit moth, Grapholita molesta in orchards

The oriental fruit moth, Grapholita molesta Busck, is a major pest of fruit trees worldwide, it is necessary to develop green control technology instead of the traditional chemical pesticide. Although the sterile insect technique (SIT) is a safe and effective method for controlling G. molesta, the high cost of mass rearing irradiated pupae hinders its widespread adoption. In this study, we identified the optimal sub-sterilizing X-ray dose for G. molesta adults and evaluated its effects on the mating competitiveness of males, growth and reproduction of the F₁ generation population, and the sterility rate of field-caught males. The results showed that the sub-sterilizing dose of 1-day-old male was 130 Gy, which rendered most males sterile (76.34%) and females nearly sterile (97.41%). Moreover, the sterile trait of the male parents that had been irradiated with 130 Gy of X-rays was successfully transmitted to the F₁ generation, whose sterility rate (84.13–93.61%) exceeded that of F₀ males. The F₁ generation population exhibited significantly lower values for the net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) compared to the non-irradiated group. Furthermore, the competitive mating index and sterility rate of irradiated males were the highest when they were paired with unirradiated males and females at a release ratio of 20:1:1. The irradiating wild males captured by sex pheromones in peach orchards with the sub-sterilizing dose achieved a 75.69% sterility rate, comparable to the laboratory-reared population. This study introduces a novel X-ray irradiation method for adult G. molesta captured in the orchard field and lays a theoretical foundation for promoting the wide application of the SIT.