Potatoes require very high fungicide inputs. New strains of late blight are hampering control measures. A monitoring aims to comprehensively record the population dynamics of the pathogen in Switzerland and provide recommendations for potato production.
With six to eight treatments per year on average – and more than fourteen in 2024 – potatoes receive more fungicidal applications than any other field crop in Switzerland.
New, more virulent strains
Parliamentary Initiative 19.475 calls for the risks associated with the use of plant protection products to be reduced by 50% by 2027. Meanwhile, the potato sector aims at increasing the use of robust varieties, with the goal of allocating 25% of the total cultivated area to robust varieties by 2028, and even 80% by 2040.
The population of the late blight pathogen Phytophthora infestans varies from year to year: new, more virulent and genetically diverse strains are jeopardising both the efficacy of fungicides and the resistance of robust varieties. Some of these potato strains can overcome resistance genes or have reduced susceptibility to key fungicides.
The population structure of the pathogen that causes late blight is poorly understood in Switzerland. This project aims to establish a comprehensive monitoring network in potato-growing areas to genetically characterise existing isolates and gain a better understanding of the composition and dynamics of the Swiss population.
The aims of the project are
- to investigate interactions between pathogens, varieties and fungicides
- to develop analytical methods for the early detection of high-risk strains
- to identify strategic sampling areas to serve as an early warning system
- to understand the selection pressure arising from agronomic practices and cultivation systems
Recommendations for practitioners
The results of this study are to be incorporated into the PhytoPRE decision support system and used to make recommendations for the control of late blight in potatoes that are adapted to farming practices. The aim is to optimise varietal selection and fungicide use (appropriate timing and use of mode of action) and at the same time reduce costs and the risk of infection. To ensure rapid transfer of knowledge into practice and boost farmers’ confidence, a network of pilot farms will be set up, and strategies will be implemented and discussed in a series of workshops.
Various workshops will be held in spring 2026 to present sample collection methods using FTA cards.
Financing / funder
- Federal Office for Agriculture (FOAG)
Project partners
- School of Agricultural, Forest and Food Sciences (HAFL)
- Research Institute of Organic Agriculture (FiBL)
Project duration
01.10.2025 to 30.9.2029
Participating Agroscope research groups
15.9 FG Cultivation Techniques and Varieties, 16.4 FG Mycology and 12.2 FG Extension Arable Crops.
