Conogethes punctiferalis (Guenée) (yellow peach moth, YPM) and Atrijuglans hetaohei (Yang) (walnut lift moth, WLM), both boring insects of walnut (Juglans regia), exhibit a competitive relationship due to occupying the same ecological niche. However, the effects of climate change, agricultural management, and irrational pesticide use on the damage caused by these insects remains unknown. Long-term field monitoring in this study revealed that populations of YPM have surpassed those of WLM on walnut since 2018, indicating that YPM, previously considered a minor pest, is now becoming a major pest. Furthermore, field survey results showed that the primary pest can complete its life history in the walnut orchard and overwinter inside fallen fruit, allowing four generations every year. Our results provide a theoretical basis for controlling YPM, currently a major pest of walnut fruit in North China.