Lymantria dispar is a quarantine pest absent in South America. A regional phytosanitary surveillance plan was developed to control this pest due to its high risk of introduction through global commerce. The objective of this study was to estimate the potential distribution ranges of L. dispar in a new geographical area, using a deductive approach to prioritize areas for preventive monitoring. In South America, forest susceptibility was evaluated under different climate scenarios. In Argentina a phenology model was simulated. According to historical climatic conditions in South America, the areas with higher risk of establishment are the Andean forests from northern Argentina to Venezuela, the Brazilian Atlantic forest, littoral coastal areas of Uruguay and Argentina and the Mediterranean area of central and southern Chile. Based on estimations of IPCC, the effects of climate change would cause a reduction of the susceptible area to L. dispar invasion in future decades. Although there were statistically significant differences among the areas with high risk of invasion, estimated by the two methodological approaches, susceptible areas for preventive monitoring were identified.