Insecticide applications against Heliothis zea Boddie, the cotton bollworm, on cotton are typically scheduled in the Texas High Plains when field sampling indicates larval densities above recommended action levels. However, use of an economic threshold does not incorporate forecasts of future numbers. Our goal was to develop and test new strategies and procedures for using a model of H. zea population dynamics as a decision aid for applying a pyrethroid insecticide. We tested a revised version of the MOTHZV model, MOTHZV10, and compared recommendations with the model to those with conventional sampling. The treatments were compared in replicated field plots using bifenthrin (Capture^®), at Halfway, Texas in 1988. Yields in check plots were 31 to 70 lbs/ac (35 to 78 kg/ha) lower than in treated plots, but these differences were not statistically different. Forecasts of larvae, damaged squares, and damaged bolls densities agreed well with field estimates. observed numbers of eggs increased after insecticide applications, whereas the model predicted decreasing numbers.