Interspecific Larval Competition of Two Diabrotica Species (Northern and Western Corn Rootworm) in Corn Roots: Implications for Pest Management

The western corn rootworm (WCR) and northern corn rootworm (NCR) are the two major belowground insect pests of corn in the U.S. Corn Belt. These species coexist in the same habitat, where their larvae feed on corn roots, increasing the risk of lodging and yield loss. Understanding larval competition between WCR and NCR is crucial for effective insect resistance management and integrated pest management. To assess interspecific larval competition between WCR and NCR, two independent greenhouse trials were conducted. We infested non-Bt corn plants with varying egg ratios of diapause and non-diapause populations of both species and counted the number of adults of each species recovered from each plant. Results showed that WCR consistently exhibited higher emergence rates than NCR, regardless of the initial egg infestation ratio. The observed ratio of NCR to WCR in both diapause and non-diapause groups was significantly lower than expected, suggesting that WCR is more competitive than NCR. The competitive dominance of WCR, coupled with climate warming, may facilitate its northward expansion across the U.S. This could potentially affect local NCR populations and further spread Bt and rotation resistance. Such changes could exacerbate pest management challenges in corn production systems. Integrating knowledge of corn rootworm competition, biology, resistance development, and climate change will be critical for developing informed management strategies to mitigate corn rootworm damage in agroecosystems effectively.