Predictability of gypsy moth defoliation in central hardwoods: a validation study

A model for predicting gypsy moth defoliation in central hardwood forests based on stand characteristics was evaluated following a 5-year outbreak in Pennsylvania and Maryland. Study area stand characteristics were similar to those of the areas used to develop the model. Comparisons are made between model predictive capability in two physiographic provinces. The tested model was inconsistent in its predictive capacity. In the Ridge and Valley province of Maryland, model predictions overestimated actual stand level defoliation. In the Appalachian Plateau of Pennsylvania, the same model underestimated stand level defoliation. The stand-based model evaluated in this study does not provide forest managers with a satisfactory method for predicting the actual amount of defoliation in a given stand. However, the model appears to be useful for estimating the relative amount of defoliation to be expected in different stands.