Optimizing insect diets for mass rearing: Investigating the role of macronutrient regulation

The codling moth (Cydia pomonella, CM) is the most serious pest of apple and pears worldwide. Pesticide overuse has led to resistance to most chemical classes, making Integrated Pest Management strategies crucial to minimize environmental impact. The sterile insect technique (SIT) is among the most environment-friendly control methods. Sterile insects that are still sexually competitive are released and by mating with wild insects help reduce the local target population. Irradiation with gamma rays produced by radioactive sources is typically used to sterilize mass-reared insects, and successfully used in Canada for CM. However, due to regulatory and cost challenges, radioactive sources are becoming increasingly less attractive. As an alternative, X-ray sterilization has been successfully explored for several Dipteran species. Lepidopterans pose challenges due to their radiation-resistance. Higher target doses required for sterilization compromise fitness. Alternatively, parents exposed to low doses of radiation produce F1 offspring with higher levels of sterility. Using a high output X-ray irradiator (XRAD 320), we report on the effects of X-ray irradiation on fecundity and sterility at doses ranging from 150 to 250 Gy. Additionally, we explored inherited sterility at lower doses (105 to 150 Gy). For all doses tested, we observed full sterility for irradiated females and a severe decrease in fertility for males. However, we did not find full sterility for the F1 generation. Our findings highlight the potential for the first X-ray-based SIT program for Lepidopterans in the USA. Further research is needed to optimize inherited sterility.