Here is a good discussion by Huub Schepers. He gives many web links to European DSS. The full paper given by Huub at the GILB'02 Conference can be read here.

DSSs integrate and organize all available information on the life cycle of Phytophthora infestans, the weather (historical and forecast), plant growth, fungicides, cultivar resistance, and disease pressure required for decisions to control late blight. Computer-based DSS that require weather information and regular late blight scouting inputs have been developed and validated in a number of European countries. In the frame of the EU concerted action “European Network for development of an integrated control strategy of potato late blight (EU.NET.ICP)” several DSSs were validated in 1999–2001 (Hansen et al., 2002). Six different DSSs were tested in validation trials in 2001: Simphyt (Germany), Plant-Plus (Netherlands), NegFry (Denmark), ProPhy (Netherlands), Guntz-Divoux/Milsol (France) and PhytoPre+2000 (Switzerland). The use of DSSs reduced fungicide input by 8–62% compared to routine treatments. The level of disease at the end of the season was the same or lower using a DSS compared to a routine treatment in 26 of 29 validations.

DSS can deliver general or very site-specific information to the users by extension officers, telephone, fax, email, SMS (short message service), personal computers and websites on the internet. Web-blight, an international information and DSS for potato late blight, provides online warning and prognosis systems for blight in the Nordic and Baltic countries and Germany. In the UK, three websites (DARD BlightNet, British Potato Council and Syngenta-UK)  are available to assist in the control of potato blight. They all use weather data from a network of local weather stations and provide area-based information on the risk of blight infection. In Germany a number of websites (ISIP Demo Daten, Bayerische LFL and Syngenta-DE) provide information on monitoring for blight and disease pressure. Recommendations are based on the DSS Simphyt. In Switzerland the internet based DSS PhytoPRE+2000  informs on infected fields. Warnings are sent to growers based on weather information, cultivar resistance and history of fungicide applications. Companies like Dacom, Opticrop and Pro-Plant have developed DSS for control of late blight and offer these services – after registration and payment – also on the Internet