Pest problems are complex and a systems view contributes to understanding their causes and assessing possible solutions. Systems approaches provide a framework for systematic analysis, synthesis and design of agricultural systems at different levels of aggregation. In systems research, the real world is divided into systems, the essence of which is captured in models. The choice of system boundaries is determined by the objectives of the study. Explanatory simulation models are based on the distinction between the process level, or explanatory level, and the system level, or level to be explained. In the course of systems research, three phases are distinguished, each with a different product: problem identification results in a conceptual model, increasing production ecological insight results in a comprehensive model, and systems design results in options and their relation to objectives of management. Various qualitative and quantitative tools are available in each of the phases. Opportunities and constraints for using systems approaches in all three phases are discussed, using illustrations at the crop, farm and regional levels.