Strategic oriented crop and pest simulation models are useful for 1) identifying conceptual weaknesses in our understanding of one or more aspects of a cropping system, 2) development of tactical guidelines for managing pest species and agronomic inputs and 3) providing a focus for the development of strategic guidelines for the development of one or more aspects of a research program. Greater the degree of biological realism embedded within these models, more likely will they be able to account for regional and site specific differences in crop growth patterns and responses to abiotic and biotic factors. From an economic perspective, however, no matter how detailed the physiologically based model, it will not be sufficiently robust to enable the impact of even the major agronomic and pest factors to be incorporated at the required level of resolution. This paper discusses converting a strategic oriented crop model into a tactical model through the development of a self-correcting algorithm, enabling site specific differences to be more realistically incorporated.