Abstract: To control the main fungal diseases in accordance with the epidemiologicaldevelopment of the fungi in viticulture, the use of forecasting systems is one of the majorprogresses. Agrometeo is an interactive platform (www.agrometeo.ch) and a general tool foragriculture, including actual and historical weather data, modules for field crops, grapevine andfruit orchards. The grapevine module contains forecasting for downy mildew and grape berrymoths; leaf area adapted spraying, growth development model, pesticides index, and descriptionsof the main diseases and pests. The forecasting modules use data from a weather station networkcovering the whole viticulture area of Switzerland. Grapevine downy mildew forecasting is donewith Vitimeteo, a new expert-system for the forecast of grapevine downy mildew, designed bythe research institute of Freiburg (Germany), Agroscope ACW and the company GEOsens. Thesoftware generates graphics and tables freely available for the growers on the Internet. Leaf areaadapted spraying was developed in analogy to the tree row volume concept on fruit orchards. Theexperiments show a reduction of about 20 to 30% of the use of pesticides by calculating theprecise dose needed for a given leaf area. The module in www.agrometeo.ch allows a ready touse solution for the calculation of the amount of plant protection products based on the width andheight of the leaf canopy and the row distance, depending on the registered amount indicated onthe package. The number of Agrometeo users is in expansion confirming the grower's interest.