Optimizing strategies for eradication of discrete-generation lepidopteran pests using inherited sterility

Population models were used to derive general principles for optimizing the success of the sterile insect technique (SIT) with inherited sterility against discrete-generation pest populations. Inherited sterility is predicted to be more effective than complete sterility whenever matings between irradiated-lineage partners are unsuccessful - this is rarely examined experimentally. Successful eradication also requires sufficient depression of fertility from matings between irradiated-lineage and wild partners, and that sufficient irradiated males are released to overcome the natural rate of increase of the wild population A critical overflooding ratio can be calculated to suggest the appropriate release rate, but because this is based on an assumption of equilibrium, the initial stages of an eradication programme with an SIT component must aim for a higher release rate than suggests. Spatial modelling suggests that, given a finite number of irradiated males available for release, the best strategy is to release these as close to the wild populations as possible. However, if the locations of all wild populations are not reasonably well known, then many small releases, regularly spaced on an area-wide basis, are more certain to achieve eradication than few large release sites. In the latter case, the total number of irradiated males required is minimized when the maximum distance between adjacent release sites is approximately the same as the average dispersal distance of irradiated males.