A spatial model of capture of Helicoverpa zea (Boddie) males in pheromone traps was developed as a UNIX script file running geographical information system commands (GRASS, v. 4.0). This model was developed to explain how spatial patterns of corn planting and wind-blocking features act to modify pheromone-trap-based earworm damage predictions on sweet corn. In the model, we sought to create a modified cumulative moth catch value that correlated more strongly with subsequent pest damage than unmodified cumulative trap catch values. The model looks at daily changes in wind direction and pheromone plume movement, calculates contribution to catch levels for all locations around the trap, and modifies the catch so that it only includes moths within the planting area of interest. We describe this model in detail and show field data results from 2 years.