The dependence of integrated pest management (IPM) on sound ecological theory has been frequently reaffirmed by both IPM practitioners and theoreticians. Insect pests, diseases, and weeds still present us with enormous challenges in all global cropping systems, and we continue to be engaged in a struggle to understand the underlying drivers of their epidemiology and the most effective management strategies. Sustainable IPM systems in the future are going to depend on significant further advances in all the sciences and technologies that contribute to insect pest, disease, and weed suppression. Although IPM systems are deeply ecological in nature, no-one can argue that we have yet defined or formalized the ways in which ecological theory can be developed and exploited to maximize their effectiveness. The application of ecological ideas in the intensely practical realm of agriculture is a slow and difficult process. In this regard the book by G. H. Walter (2003) may serve as a preamble to this volume; although focused on insects, Walter's comments are equally applicable to plant pathogens and diseases. In it Walter states that “Insect ecology research for IPM purposes is represented by a rather grey area; the linkage between theory and practice is still not explicit.” We think that some of the chapters in the present book offer insights arguing that ecological theory has already provided the foundation for some level of IPM. Unquestionably, however, much more research must be done to fully integrate ecological theory into IPM practice.