Potatoes are Switzerland’s most fungicide-intensive crop, with 6–7 late blight treatments per year, and over 14 in 2024. To meet the Swiss plant protection plan of halving pesticide risks by 2027, the sector aims for 25% robust varieties by 2028 and 80% by 2050. Yet, late blight populations are evolving, with new, virulent, and genetically diverse strains threatening fungicides and resistant varieties. Some strains can overcome resistance genes or show reduced fungicide sensitivity. In Switzerland, little is known about this pathogen’s population structure. A national sampling network will therefore be established to analyze population dynamics. The project aims to:

1. study interactions between pathogen, varieties, and fungicides;
2. develop tools for early detection of high-risk strains;
3. identify strategic sampling areas for early warnings;
4. assess selection pressures from agronomic practices.

Results will feed into PhytoPRE, offering tailored recommendations to optimize variety and fungicide use while lowering risks. To ensure rapid uptake and farmer trust, pilot farms and workshops will implement the strategies.