Mullein plant bug damage is unpredictable. Sometimes, even when there are high nymph numbers, there is no damage. This is probably due to asynchrony between mullein bug egg hatch and apple bloom; apples are only susceptible from bloom through when fruit are about 0.5 inch diameter. Insecticides must be applied at the pink bud stage to prevent all economic damage. To avoid using insecticides unnecessarily at the pink stage, we need to be able to predict whether mullein bug egg hatch will occur when the crop is susceptible. To accomplish this we are comparing simulation models of MPB development and apple development for their ability to predict pest/crop synchrony under different winter and spring temperature scenarios. Results of model runs will be compared to historical data on pest/crop development and damage incidence. At this point in this multi-year project, models are being constructed. In addition, Red Delicious trees will be planted in pots, infested with mullein bugs by placing them in infested orchards, then subjected to various temperature scenarios, similar to those used in the model runs. Supplies have been ordered for planting in spring 2004.