Monitoring of potato late blight in Switzerland and development of PhytoPRE+2000, an internet based decision support system

Since 1990 late blight (LB) epidemics are monitored in Switzerland with a LB observation network of untreated potato plots. In addition, information about the first disease observations in the commercial potato production has been collected and used for local and regional warnings. In 10 out of 12 years the epidemic started already in May. In 9 out of 12 years the first LB attacks were found in early, previously covered potatoes. From 2001, Swiss potato growers will be supported by an Internet based version of the LB decision support system (DSS) PhytoPRE+2000. Core parameters of this DSS are the actual state of the national LB situation and historical and forecasted weather data. The weather data are used to recognise main infection and sporulation periods (MISP) of Phytophthora infestans . From 1996 to 2000, the MISP model was used in field trials as a trigger of LB fungicide applications. Compared to PhytoPRE+95 no reduction in fungicide treatments could be realised in wet years, but up to 40% in rather dry years. In field trials the MISP triggered LB control was as good as in PhytoPRE+95 or at least as good as those of other DSSs tested in Swiss field trials. In 1999 and 2000, the MISP model was embedded in the new DSS PhytoPRE+2000. To assure an efficient information exchange an Internet solution was selected. PhytoPRE+2000 is a DSS for local and field specific LB recommendations and a comprehensive LB information and warn system. Daily actualised disease maps and MISP graphs can be accessed on the Internet and illustrate the LB risk situation for all Swiss potato growing areas. The structure of PhytoPRE+2000 was determined in a close cooperation with the Swiss potato growers association and the cantonal plant protection services.