Abstract Understanding and predicting the impact of climate change on population demography, biotic interactions and ecosystem service is central to ecology. Long-term time series analysis of insect populations is crucial for analyzing the effect of climate change on plant–insect interactions in agro-ecological systems; yet such data are often lacking. Here, based on field experiments and the long-term time series of the overwintering adult cotton bollworm Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) collected since 1975, we investigate the dynamic trend of H. armigera, as well as its driving forces and effects on the recruitment of H. armigera and crop yield. Results illustrated a shift to early eclosion of diapausing pupae due to global warming, extending the duration and abundance of adults in the overwintering generation. This then led to more larvae recruited in the first generation, and consequently damages the wheat at early growing stages. Our results suggest that the asynchronous effects of rising global surface temperature on the relative growth rate of spring crops and insect pests could intensify in the future, causing accentuated crop yield loss. To mitigate the adverse herbivore-mediated effect on crop yield in a warming climate, efficient cultivation measures and pest management are necessary, such as planting precocious crops with short growth period and timely control of insect pests.