Black rot on grapevine is a fungal disease c a u s e d b y P h y l l o s t i c t a a m p e l i c i d a (s y n. Guignardia bidwellii) affecting grape leaves as well as clusters. A novel black rot decision support system termed VitiMeteo Black rot was assembled based on existing sub-models and incorporated into the established VitiMeteo forecast and decision support platform. Based on local weather data and a 5-day weather forecast, VitiMeteo Black rot simulates the relative susceptibility of grape clusters, the occurrence