Host-Pathogen Population Cycles in Forest Insects? Lessons from Simple Models Reconsidered

A host-pathogen model with free-living infective stages and host self-regulation has been investigated with a view to clarifying the possible role of pathogens in the cyclic dynamics of forest insect pests generally, and of a granulosis virus in the dynamics of the larch budmoth in particular. Contrary to previous related analyses, lacking self-regulation, no support is provided for the view that host-pathogen interactions alone are capable of generating cyclic dynamics of the type observed in forest Lepidoptera. Overall, cycles 'ire less likely here than in the absence of simple self-regulation, and parameters from field estimates usually fail to generate cycles