Climate change favours a destructive agricultural pest in temperate regions: late spring cold matters

Global climate change has profound consequences on survival and reproduction of arthropods. In particular, in temperate regions changes in spring temperatures have a major impact on crop pest population dynamics, but the mechanisms remain elusive. By analysing empirical data of Helicoverpa armigera moth populations from three sites over 12-13 years in northwestern China, and running modelling (DYMEX software), we intended to clarify how the late spring cold (LSC) events affect the populations of this destructive pest species. We then explored the relationships between LSC parameters and moth population dynamics using model simulations. Our results highlight the importance of LSC in driving H. armigera population dynamics. Of the LSC parameters tested, the duration of LSC measured as the maximum continuous days with a minimum temperature lower than 10 degrees C (MCDL) was a key factor influencing the population abundance of the spring and summer generations. Furthermore, the model showed that the timing of the LSC event had a major effect on how the MCDL influenced each generation. The timing with respect to the eclosion of the overwintering generation was critical, and it determined the variation in the abundance of the first and subsequent generations. Our findings imply that the abundance of H. armigera will increase as the frequency and duration of LSC events decrease under global spring warming. Incorporating the duration and timing of LSC events into decision-making should improve forecasting H. armigera abundance and other insect species under global climate change and better inform pest management