EuroBlight’s first 2025 potato season results show Europe’s late blight population remains dominated by the aggressive EU36 genotype, while EU43 and EU46 strains continue shifting regionally. More than 1,200 samples were genotyped, revealing rising diversity in northern and eastern Europe. Adjusted fungicide strategies have helped suppress resistant strains, but late blight still causes major economic losses across Europe and worldwide.
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The EuroBlight monitoring team — which tracks and responds to the challenges posed by early and late blight in Europe and beyond — has released its first results from the 2025 potato season. The early update comes as growers remain concerned about the spread and impact of newer late blight strains, particularly the EU43 and EU46 clonal lineages of Phytophthora infestans.
Scientists at The James Hutton Institute play a central role in EuroBlight’s work, contributing to both the consortium’s management group and the analysis of submitted samples. EuroBlight is a multidisciplinary, multi-actor network that was originally launched with EU funding.
“Warm and dry weather across many potato-growing regions last year, especially from March to July, reduced blight pressure for much of the season. More than 1,200 samples from sponsors across Europe were genotyped,” Dr. David Cooke said.
Key findings so far
- The P. infestans population in Europe remained dominated by the EU36 genotype, which made up around one third of samples.
- The decline in EU43 has stabilised. Its overall frequency rose slightly but increased strongly in France. EU43 was also found in Switzerland and Latvia for the first time.
- EU46 increased from 4% to 7% of samples and spread to more countries, including England, Norway, Sweden, Latvia and France.
- EU36 dominated in western and central Europe, while more genetically diverse “other” types were more common in north-eastern Europe.
- The relatively new clones, EU43 and EU46, with reported resistance to some active fungicide ingredients, have been broadly suppressed through modified approaches to fungicide use, with more mixing and alternation of the Fungicide Resistance Action Group (FRAC) active ingredient groups. More information on EU43 and EU46 and fungicide resistance can be found in this recent paper, New Mechanisms of Resistance to CAA and OSBPI Fungicides in Phytophthora infestans
- The overall frequency of EU43 had decreased from 23% in 2023 to 9% in 2024 with a slight increase to 12% of all early samples in 2025, and a marked variation between countries
- Netherlands reported 20%, from a sample of 69
- Germany,12% from a sample of 58
- Belgium, 13% from a sample of 30
- Denmark 4% from a sample of 103
- France a notable increase from 10% to 25%, from a sample of 345
Although the frequency of EU46 sampled across European crops increased from 4% in 2024 to 7% in 2025, again there was considerable regional variation.
- Decreased in the Netherland to 1%, from a sample of 69
- Not detected in Denmark, from a sample of 103
- Increased in Belgium to 5%, from a sample of 39
- Increased in Great Britain to 20%, from a sample of 278
- Broadly the increase due to a range expansion to England, Norway, Sweden, Latvia and France
EU36 is an aggressive genotype and dominant across many parts of Europe, though there was a fall in overall frequency from 52% in 2024 to 34% in 2025. Once more, there was considerable regional variation
- EU36 made up 43% of samples in the Netherlands
- 64% in France, and
- 74% in Belgium
- Bar a single sample in Denmark, it was not found in the Nordic countries
Other blight clones of note:
- EU41 increased slightly from 2% in 2024 to almost 5% in 2025 and remains localised, mainly in Norway and Denmark, where it comprised 2-5% of the population and in Scotland, where it comprised 25% of the 113 samples. In Denmark, all 10 isolates of EU41 were found at the same trial location
- EU45 which had been steadily expanding after its initial sampling in 2019, to comprise 4% of the samples in 2024, fell to 1% with its range expanded to eight countries, including Poland
- EU37, which is resistant to fluazinam, stayed at a very low level, around 1%, compared to its high of 14% in 2017 and 2018
- EU47, which has novel virulence against R8 and R9 resistance genes, was first reported in 2024 but was not detected in 2025. This may be linked to the reduced blight pressure and smaller population size
Around one-third of samples were assigned to the highly diverse “Other” category — about twice the share reported in 2024. This shift reflects a larger proportion of 2025 samples coming from northern and eastern regions, where P. infestans populations are less dominated by established clonal lineages. In Denmark and Norway, for instance, 85% of samples were classified as “Other.”
Long-term datasets show a steady presence of highly localised, short-lived multi-locus genotypes that never become widespread enough to be designated as named clones. This pattern is consistent with infections arising from oospore inoculum in the soil, where oospores germinate and trigger local outbreaks.
According to a press release, late blight remains a major threat to potato and tomato crops globally. In Europe alone, late blight costs an estimated €900 million each year in control measures and crop losses, rising to more than €5 billion worldwide.
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