Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2022
Publication Date: 3/1/2022
Citation: Sisterson, M.S. 2022. Mitigating an epidemic of resistance with integrated disease management tactics: Conflicting management recommendations from insecticide resistance and epidemiological models. Phytopathology. 112(8):1753-1765. https://doi.org/10.1094/PHYTO-09-21-0386-R.
Interpretive Summary: Insect transmitted plant pathogens threaten agricultural production worldwide. Insecticide treatment thresholds for vectors of plant pathogens are low as a single feeding bout may result in transmission of a pathogen that could kill the plant. Reliance on insecticides for suppressing vector populations has resulted in evolution of insecticide resistance in a wide range of systems. Analysis of evolutionary and epidemiological models indicated that conditions associated with successful disease control using insecticides were associated with rapid evolution of insecticide resistance. Likewise, conditions that delayed insecticide resistance were associated with rapid pathogen spread. To reduce risk of insecticide resistance, reliance on insecticides must decrease and additional tactics to suppress pathogen spread must be adopted. Accordingly, the models were used to evaluate effects of integrating application of insecticides with mating disruption and deployment of partially resistant plants. Model results demonstrated that by targeting multiple aspects of the plant-pathogen-vector systems, pathogen spread could be suppressed and resistance delayed. Results provide a conceptual framework for researchers developing methods to slow spread of insect transmitted plant pathogens.
Technical Abstract: Insect transmitted plant pathogens threaten crop production worldwide. As a single feeding bout may be sufficient for a vector to transmit a pathogen that kills the plant, treatment thresholds for vectors of plant pathogens are low. For many vector species, overreliance on chemical controls has resulted in evolution of insecticide resistance. Analysis of complementary insecticide resistance and epidemiological models indicated that tactics for delaying resistance evolution conflict with tactics for limiting pathogen spread. Insecticide resistance models support maintaining untreated refuges that serve as a source of susceptible insects that reduce likelihood of mating among rare resistant insects. In contrast, epidemiological models indicate that movement of vectors from untreated areas to insecticide treated areas contributes to pathogen spread. Accordingly, epidemiological models support area-wide insecticide spray programs, although resistance models indicate that such an approach is likely to lead to rapid resistance. To mitigate risk of insecticide resistance, additional management approaches must be integrated into plant disease management strategies. The resistance and epidemiological models were used to evaluate effects of integrating application of insecticides with two additional management strategies: deployment of partially resistant plants (plants that are not immune to infection but have lower acquisition and inoculation rates than susceptible plants) and mating disruption (reduced vector birth rate in mating disruption treated areas). Deployment of partially resistant plants reduced risk that untreated areas served as a source of inoculative vectors. Mating disruption reduced risk of resistance by suppressing growth of insecticide resistant populations and benefited disease management by reducing vector abundance. Simulation results indicated that by targeting multiple aspects of the plant-pathogen-vector system, pathogen spread could be suppressed and resistance delayed. Implementation of such an approach will require innovations in vector control and sustained efforts in plant breeding.