Optimization of X-ray irradiation dose and cold storage conditions for substerile Spodoptera litura (Lepidoptera: Noctuidae) to be employed in sterile insect program.

The sterile insect technique (SIT) represents an environmentally benign pest management strategy. Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a highly polyphagous pest, poses a significant threat to global agricultural productivity. To enable effective SIT implementation, we determined the optimal X-ray irradiation dose required to induce near-complete sterility across parental and F1 generations while evaluating the cold storage tolerance of irradiated pupae. This study lays a critical foundation for integrating sterile S. litura into field-based suppression programs. Our results establish 105 Gy as the optimal X-ray irradiation dose for 7-day-old S. litura pupae. This dose induced over 84% infertility in parental males, more than 90% infertility in F1 males, and nearly complete infertility in F1 females. However, mating success was reduced to 53.4%, with a control value of 92.5%. Although parental sterile males exhibited a lower average mating times (2.85) relative to the control group (4.95), this dose had no adverse effect on their single-mating duration or flight capacity. Post-irradiation cold storage trials revealed 12°C for 7 days minimized adverse impacts on sterile males. Furthermore, after 7 days of cold storage at 12°C, flight duration and distance decreased by 14% and 17%, respectively. The highest mating competitiveness (C = 0.51) was achieved with a 9:1:1 release ratio (cold-stored irradiated males: normal males: normal females), whereas the 1:1:1 ratio yielded a considerably lower C value of 0.07. X-ray-induced sterility in S. litura demonstrates substantial potential for practical field application. Coupled with an optimized cold storage strategy, this study facilitates the scalable production of competitive sterile males, greatly advancing SIT operational feasibility against this polyphagous pest.