Many grain storage elevator operators have been reluctant to adopt IPM practices. Previous work has found that although IPM reduces pesticide use and associated costs, it requires more management skill and labor, both expensive inputs. So, some IPM practices are more expensive than conventional chemical-based practices, while some are less expensive. However, no studies have measured the costs of grain damage caused from incompletely controlling insects. Applying treatments when they are not needed adds unnecessary, though typically small, costs. However, not applying treatments when they are needed results in large costs due to grain damage discounts. An insect growth model is used to predict numbers of grain-damaging insects in a storage facility so that economic damages from failing to control insects can be estimated. When both treatment cost and grain damage cost are considered, automatic aeration is the best practice. However, aeration is not available for many elevators with concrete silos. For those elevators, routine fumigation is less expensive than selective fumigation based on grain sampling for many locations. In those locations, sampling changed only the timing, not the frequency, of fumigation. Thus, it may be rational for many elevators to forego IPM practices based on sampling.