This presentation will help consultants, practitioners, and growers to understand late blight forecasts and to manage late blight more effectively. The presentation begins by describing the epidemiological basis for potato late blight forecasts. In the potato production system in most temperate regions where sexual reproduction does not occur, survival from one season to the next is in association with an infected host (typically, potato tubers). Most forecasts allow a period early in the season before which fungicide sprays are not necessary; the presentation also describes the most popular systems in the United States. The presentation then describes a decision support system (DSS) that can be used in real time as an aid in scheduling fungicide sprays. The DSS integrates the effects of weather, host resistance, and fungicides to ensure adequate disease suppression.