Pesticide resistance and ectoparasites associated with urban pests: Genetic, evolutionary, and pest management perspectives

Urban pest management faces increasing challenges from pesticide resistance and a lack of research on important pest groups, such as the ectoparasites of commensal rodents. This dissertation examines the mechanisms driving insecticide and rodenticide resistance in bed bugs and commensal rodents, and investigates the prevalence of ectoparasites associated with house mice. The first part of the dissertation evaluates the efficacy of commonly used insecticides against field-collected populations of the common bed bug (Cimex lectularius L.) and the eastern bat bug (C. adjunctus Barber). The results indicated that most field bed bug populations were highly resistant to pyrethroids, while they had low to no resistance against neonicotinoids. The eastern bat bug showed similar susceptibility to insecticides as the laboratory bed bug strain. Further investigation into highly resistant bed bug populations demonstrated that both biochemical detoxification and molecular target-site mutations (kdr) contribute to deltamethrin resistance, underscoring the combined mechanism of resistance evolution. A temporal analysis of kdr mutations in bed bugs collected across New Jersey over 15 years revealed a fixation of resistance-associated alleles, highlighting continuous selection pressure from pyrethroids and the persistence of resistant genotypes in field populations. Expanding the scope to commensal rodents, this dissertation identifies Vkorc1 mutations associated with anticoagulant rodenticide resistance in house mice and Norway rats sampled from the northeastern United States. The high prevalence of Vkorc1 mutations in house mice indicated the potential control failure by rodenticides in the future. In contrast, low prevalence of Vkorc1 mutations in Norway rats implied that integrated pest management (IPM) programs are essential to reduce the risk of resistance development. Additionally, surveys of ectoparasites from urban house mice uncovered prevalent and abundant assemblages, revealing potential risks for pathogen transmission. All research demonstrate that chemical resistance in urban pests is widespread and driven by complex genetic and biochemical factors. Continued resistance monitoring and incorporation of molecular tools and host–parasite interactions into modern IPM programs are needed.