Heterogeneity of selection and the evolution of resistance

The evolution of resistance to pesticides and drugs by pests and pathogens is a textbook example of adaptation to environmental changes and a major issue in both public health and agronomy. Surprisingly, there is little consensus on how to combine selection pressures (i.e., molecules used in the treatment of pests or pathogens) over space and time to delay or prevent this evolutionary process. By reviewing theoretical models and experimental studies, we show that higher levels of heterogeneity of selection are associated with longer-term sustainability of pest or pathogen control. The combination of molecules usually outcompetes other resistance management strategies, such as Responsive alternation, Periodic application, or Mosaic, because it ensures 'multiple intragenerational killing'. A strategic deployment over space and/or time of several combinations can ensure 'multiple intergenerational killing', further delaying the evolution of resistance.