Models of intermediate complexity in insect-pathogen interactions: population dynamics of the microsporidian pathogen, Nosema pyrausta, of the European corn borer, Ostrinia nubilalis

Abstract

SUMMARYNosema pyrausta is an important microsporidian pathogen of the European corn-borer, Ostrinia nubilalis (Pyralidae), a major pest of corn (maize). The population dynamics of the interaction between the moth and its pathogen have been studied previously using simple models phrased as coupled differential equations, and using large simulation models containing over 150000 coupled equations. A middle approach is adopted here and the interaction studied using an age-structured model written as a system of delay-differential equations. Although the model contains twenty four parameters, estimates for twenty of these were available in the literature. Our model provides a good qualitative match to observed within and between season dynamics and suggests which aspects of the interaction are most important in determining the nature of the system's population dynamics. More generally, we argue that in the absence of better data on insect-disease interactions in natural habitats, valuable insights can be gained by studying equivalent systems in agro-ecosystems. We also argue that models of intermediate complexity that incorporate considerable detail about the natural history of individual interactions, but which are derived from the classical models of animal ecology and epidemiology, offer the most profitable way of modelling insect-pathogen interactions in the wild.