Inheritance and fitness costs of field‐evolved resistance to Gpp34/ Tpp35Ab1 corn by western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)

BACKGROUND: The western corn rootworm, Diabrotica virgifera virgifera LeConte, is among the most serious pests of corn in the United States, and an invasive pest in parts of Europe. In the United States, feeding injury to roots by western corn rootworm larvae is managed, in part, with genetically modified corn hybrids that produce insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt). The widespread use of Bt corn has contributed to field-evolved resistance to all commercially available Bt traits by some western corn rootworm populations. Insect resistance management (IRM) plans for Bt crops in the United States use the refuge strategy to delay evolution of resistance. Mating of susceptible individuals from refuges with resistant individuals produces progeny that are heterozygous for resistance, and delays resistance compared to a scenario where refuges are absent. Two factors that strongly influence the delays in resistance achieved by the refuge strategy are the inheritance and fitness costs of resistance. RESULTS: Our research found that field-evolved resistance to plants that express the Bt protein Gpp34/Tpp35Ab1 protein by western corn rootworm was inherited in a non-recessive manner and associated with some fitness costs. CONCLUSION: The non-recessive inheritance of Gpp34/Tpp35Ab1 likely will diminish the capacity of refuges to delay resistance and heighten the risk of resistance evolution. However, this effect may be counterbalanced to some degree by fitness costs. This evidence suggests that IRM strategies for western corn rootworm with larger refuge sizes and more diversified management approaches could reduce the risk of resistance evolution. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.