Comparison of cold tolerance between western corn rootworm and northern corn rootworm

The western corn rootworm (Diabrotica virgifera virgifera, WCR) and the northern corn rootworm (Diabrotica barberi, NCR) are the two major belowground pests of corn and have caused substantial yield losses and economic damage in the U.S. Corn Belt. Cold tolerance and diapause are key physiological strategies that enable insects to survive harsh winter conditions. Both NCR and WCR overwinter in the soil by undergoing egg diapause. Notably, some NCR populations exhibit extended diapause lasting up to two years, which serves as an adaptive strategy that allows synchronization of their life cycle with the availability of preferred host plants, thereby enhancing survival and reproductive success. Given the importance of overwintering success for pest management, this study aims to compare the cold tolerance of NCR and WCR eggs. Eggs from both diapausing and non-diapausing colonies of NCR and WCR were used in this study. To simulate diverse soil moisture conditions experienced in the field, eggs were subjected to three moisture levels and then cold tolerance was evaluated by measuring the supercooling point, water content, carbohydrate reserves, and egg hatching rate after cold exposure. The results will enhance our understanding of interspecific and intraspecific variation in cold tolerance among Diabrotica populations and provide a scientific basis for predictions of overwintering success and guiding region-specific pest management strategies under changing climatic and soil conditions.