EuroBlight final data release, 2024
EuroBlight releases the final set of genotype results, 2024, - now totalling approximately 3000 results from all over Europe.
Given concerns at the impact of novel genotypes of P. infestans, the EuroBlight monitoring team here releases a final status of the 2024 population.
Key findings:
- Late blight pressure in 2024 was again higher than average across many parts of Europe and fungicide resistance concerns resulted in high sampling intensity. Disease outbreaks from 27 European countries were sampled by 37 teams in 2024 with almost 3000 samples successfully genotyped.
- The frequency of genotype EU43 decreased from 23% in 2023 to 9% of the population in 2024. Though it has extended its range to 14 European countries.
- The EU46 clone, related to EU43, that emerged in 2023 has increased from 3.5% of the population to 4% and now sampled in 7 countries.
- In 2024, across much of Europe more intense fungicide programmes with a strict focus on mixing and alternating active ingredients has had the desired impact of reducing losses caused by resistance to the CAA and OSBPI fungicide groups. This has checked the rise of the EU43 and EU46 genotypes.
- Similarly, the frequency of the EU37 clone with reduced sensitivity to fluazinam has continued to decline; falling from 1.8 in 2023 to 0.6% of the sampled population in 2024.
- Comprising 52.5% of the 2024 samples and across 27 countries, EU36 was the most frequently sampled genotype suggesting it remains fitter than other clones. Under strong selection pressure mutations in EU36 have been reported that create novel virulences and cause fungicide resistance.
- In 2024 a new clone, EU47, was defined which has been spreading on specific blight resistant cultivars since 2021 and now across three countries. Sampling metadata suggests its emergence is based on a novel virulence profile.
- Primary inoculum is locally generated and spread indicating that better management of all inoculum sources is required.
- The proportion of ‘other’ genotypes generated from sexual oospore inoculum was lower than average at 14.8% of the population but this reflects increased sampling in areas dominated by clones rather than a reduction in the significance of this inoculum source.
- Genotyped samples with results, EU, 2024 n=2914 by 28 May 2025
Figure 1. Distribution of genotypes in 2024 season, frequency chart
Figure 2. Minimum spanning network showing the genetic relatedness of genotypes sampled in 2024.
How did we do it?
Since its arrival in the nineteenth century, Phytophthora infestans, the cause of potato late blight, has remained an ongoing threat to European potato production. Although we are now better equipped to control the disease than in the past, evolving pathogen populations continue to challenge integrated management practices. Changes in populations of P. infestans directly influence the effectiveness of cultivar resistance, the performance of disease warning systems and the efficacy of plant protection products.
Co-ordinated and continuous EuroBlight pathogen monitoring has thus been implemented as an EU-wide monitoring activity supported by many stakeholders since 2013. The monitoring and characterisation of the population changes and invasive genotypes helps to optimise integrated pest management (IPM) strategies, as required by EU Directive 2009/128/EC on the sustainable use of plant protection products.
FTA sampling cards onto which lesions had been pressed were returned to laboratories (Hutton, INRAE and IHAR) for pathogen DNA fingerprinting using simple sequence repeat (SSR) markers. Samples were assigned to existing clonal genotypes or defined as new genotypes and all results uploaded to the EuroBlight database (www.euroblight.net). Support from international groups is generating similar data for parts of Asia, South America and Africa, to detail a global understanding of pathogen population change.
A wet winter and spring in many parts meant blight pressure was high from the start which, in combination with concerns about fungicide resistance, resulted in the highest ever annual EuroBlight sample size. Results for 2904 samples are mapped (Figure 1) and the genotype data from 2013-2024 now comprises over 21,000 samples from 37 European countries. We thank all sponsors and partners who have provided samples.
Across the European potato crop, the decline in samples of the EU43 clonal lineage from 23% to 9% is positive news. Resistance in the EU43 lineage to both mandipropamid and other CAA fungicides plus the OSBPI oxathiapiprolin resulted in positive selection pressure and an increased frequency over recent seasons. However, as proven by the Danish monitoring results in 2023, a widespread and decisive change in approach to fungicide programmes in 2024, with more intensive use plus a sharp focus on the mixing and alternation of active ingredients, appears to have suppressed the frequency of EU43. Nonetheless, the range of EU43 increased to 13 countries with new reports in Poland, Austria, Italy and Serbia in 2024 and an increase in frequency in France from 4 to 10%. The declines in the proportion of EU43 from the 2023 to 2024 seasons were most marked in the Netherlands (55 to 17%), Germany (50 to 15%) and Denmark (19 to 6%). Surprisingly, EU43 has yet to be sampled in UK crops despite its presence to the west in Ireland.
Unlike EU43, the frequency of EU46 increased slightly from 3.5 to 4.0 % of the overall population with the highest frequency in Germany at 18% of samples (up from 14% in 2023). Its range expanded from 3 countries to 7 with new samples from Belgium, Poland, Scotland and Wales found in 2024. Isolates of EU46 are reported to be resistant to oxathiapiprolin but mostly sensitive to mandipropamid. It is unclear why this lineage, that is closely related to EU43, did not mirror its decline.
Genotype EU36 was the most frequently sampled from outbreaks in 2024 with the proportion up from 37% in 2023 to 53% in 2024. It is now found in 27 European countries with the biggest increases in the Netherlands (23 to 61%) and Belgium (46 to 81%) and with stable high proportions in France (74%) and England (76%). This clone has been steadily increasing since it was first sampled in 2013 and is reported to generate large lesions with abundant sporangial production. Its high incidence has resulted in genetic changes that have enabled it to overcome some cultivar resistance and a low frequency of EU36 samples are reported to be resistant to oxathiapiprolin. This demonstrates that, given exposure to sufficient selection pressure, problematic DNA mutations may occur in any lineage of P. infestans.
From its highest sampled frequency of 14% in 2018, EU37 has continued a steady decline to less than 1% of the European samples in 2024. Isolates of this lineage showed resistance to fluazinam and its decline in incidence mirrors a reduction in the overall use and pattern of usage away from ‘blocks’ (consecutive applications of the same active). This suggests that without the selection pressure of fluazinam use, isolates of EU37 are not as fit as those of other lineages. This is a success story for EuroBlight as it has maintained fluazinam as a valuable component of fungicide programmes when used in accordance with FRAC guidelines in 2024.
A new lineage, called EU_47_A1 (EU47) was defined in 2024. Since it was localised and sampled at a low frequency in a single region of the Netherlands it had been reported as an ‘Other’ since 2021. However, it was named in 2024 because it was sampled 31 times, comprised 6% of the Dutch pathogen and had spread to Belgium and Switzerland. The sample metadata shows that isolates of this lineage are sampled at a disproportionally high frequency from cultivars matching one of the Wageningen Task Force Plantum host resistance groups. This is the first known case of a clonal lineage of P. infestans that appears to have emerged and spread due to its virulence traits and it illustrates that knowledge of the population can inform fungicide use and host resistance deployment in support of IPM.
The EU45 clone is also showing a steady increase in sampling frequency and comprised 4% of the population in 2024. It was first sampled in southern Germany in 2019, has progressively spread across central Europe and extended its range to Austria and Switzerland in 2024. More research is required to understand the phenotypic traits of this clone. Conversely, EU41 is showing a progressive decrease in frequency despite an increased in UK crops in 2024.
Older genotypes such as EU13 and EU6 have continued to decline and are confined to countries in the west of Europe. From around one quarter of the population in 2014, EU13 comprised only 2% of the 2024 sample. Although EU6 remains at 7% of the sampled population in 2024, most of these were from UK crops.
Lastly, the genetically diverse ‘Other’ samples comprised 15% of the sampled population in 2024 which was lower than the 26% mean proportion from 2013 to 2024. This reduction probably reflects the more intense sampling of the lowland and western potato growing parts of Europe that are dominated by clones than in recent years. A remarkable 85% of the Danish sample comprised ‘Other’ in 2024 which was consistent with warm, wet conditions that promoted oospore germination and plant infection early in the potato growing season. Conversely all of the samples from France in 2024 were of known clonal lineages. These diverse range of genotypes are most prevalent in crops in the north and east of Europe (Figure 1) and are consistent with a soil-borne source of sexual oospores. There are ongoing epidemiological threats of earlier primary inoculum and evolutionary advantages to sexual recombination generating pathogen phenotypes within these oospore-borne populations.
The genetic diversity of the 2024 population has been visualised (Figure 2) using an analysis tool (poppr 2.0) linked to the EuroBlight pathogen database. The minimum spanning network shows sub-clonal diversity within each of the genotypes (also known as clonal lineages). The clonal and within-clone variation is being used to track the evolution and spread of these pathogen populations across Europe and beyond. ‘Other’ isolates (not shown) are genetically diverse and distributed across the whole network.
The results of the 2024 monitoring emphasised the value of the EuroBlight pathogen tracking. It continues to provide a cost-effective and co-ordinated approach to understanding pathogen evolution on a European scale. Data on the dominant genotypes have been passed to growers, advisors, breeders and agrochemical companies to provide timely practical advice in support of potato blight control. Working with our key sponsors, we succeeded in providing within-season feedback and a November 2024 update that helped shape advice and the discussions of the FRAC fungicide resistance committees for any updates to advice for the 2025 season. It remains clear that in combination with SSR genotyping we more phenotyping of virulence and fungicide sensitivity data is also required on a European scale in support of IPM.
The EuroBlight network continues to harmonise methods with other networks in the Americas, Asia and Africa and encourages continued co-operation between groups involved in managing late blight to exploit the database and tools for improved awareness and blight management on a global scale. Please contact the project team if you would like more information or if you would like to contribute in 2024. We thank all the partners who have contributed samples and thus sponsored this project.
We thank the following participants/sponsors who have contributed to the 2013-2024 monitoring.
Aarhus University, ACVNPT, ADAMA, AFBI, Agrifirm, Agricultural Institute of Slovenia, Agrico, Agriphar, Agroscope, AHDB Potatoes, ARVALIS-Institut du Végétal, BASF SE, Bayer AG CropScience Division, Bayerische Landesanstalt für Landwirtschaft, BSV Network (France), Bejo, Centre Wallon de Recherches Agronomiques, Certis Belchim, Cheminova, Corteva, CropSolutions, CUConsulting, CZAV, Delphi, Emsland Group, EMU, Estonian University of Life Sciences, Eurofins, Fight Against Blight (UK sponsors), Germicopa/ Florimond Deprez, Hochschule Osnabrück, HZPC Holland B.V., INRAE, Institute of Plant Protection and Environment in Serbia, The James Hutton Institute, Julius Kuehn Institute, LfL Bayern, Meijer Potato, Neiker, Nordisk Alkali, Norwegian Agricultural Advisory Service, NIBIO, PCA, The Plant Breeding and Acclimatization Institute (IHAR), Pepsico, Petla, Profytodsd, RML Iceland, Swedish University of Agricultural Sciences, Solynta, SRUC, SynTech Research, Staphyt, Syngenta, TEAGASC, Technical University of Munich, UPL, Van Iperen, Vertify, University of Bologna, University of Fribourg, University of Vigo, and Wageningen Research.
Genotype maps and charts are available here:
https://agro.au.dk/forskning/internationale-platforme/euroblight/pathogen-monitoring/genotype-map
Contacts
- Jens G. Hansen & Poul Lassen, Aarhus University. Contact: jensg.hansen@agro.au.dk
- David Cooke & Alison Lees: James Hutton Institute, Dundee. Contact: david.cooke@hutton.ac.uk
- Geert Kessel, Wageningen University and Research Centre. Contact: geert.kessel@wur.nl
- Didier Andrivon & Romain Mabon, INRAE. Contact: Didier.Andrivon@inrae.fr
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