Earlier occurrence and increased explanatory power of climate for the first incidence of potato late blight caused by Phytophthora infestans in Fennoscandia

Research output: Contribution to journalArticle


Background Late blight (caused by Phytophthora infestans) is a devastating potato disease that has been found to occur earlier in the season over the last decades in Fennoscandia. Up until now the reasons for this change have not been investigated. Possible explanations for this change are climate alterations, changes in potato production or changes in pathogen biology, such as increased fitness or changes in gene flow within P. infestans populations. The first incidence of late blight is of high economic importance since fungicidal applications should be typically applied two weeks before the first signs of late blight and are repeated on average once a week. Methods We use field observations of first incidence of late blight in experimental potato fields from five sites in Sweden and Finland covering a total of 30 years and investigate whether the earlier incidence of late blight can be related to the climate. Results We linked the field data to meteorological data and found that the previous assumption, used in common late blight models, that the disease only develops at relative humidity levels above 90% had to be rejected. Rather than the typically assumed threshold relationship between late blight disease development and relative humidity we found a linear relationship. Our model furthermore showed two distinct responses of late blight to climate. At the beginning of the observation time (in Sweden until the early 90s and in Finland until the 2000s) the link between climate and first incidence was very weak. However, for the remainder of the time period the link was highly significant, indicating a change in the biological properties of the pathogen which could for example be a change in the dominating reproduction mode or a physiological change in the response of the pathogen to climate. Conclusions The study shows that models used in decision support systems need to be checked and reparametrized regularly to be able to capture changes in pathogen biology. While this study was performed with data from Fennoscandia this new pathogen biology and late blight might spread to (or already be present at) other parts of the world as well. The strong link between climate and first incidence together with the presented model offers a tool to assess late blight incidence in future climates.


  • Veiko Lehsten
  • Lars Wiik
  • Asko Hannukkala
  • Erik Andreasson
  • Deliang Chen
  • Tinghai Ou
  • Erland Liljeroth
  • Åsa Lankinen
  • Laura J. Grenville-Briggs
External organisations
  • Swiss Federal Institute for Forest, Snow and Landscape Research
  • Swedish University of Agricultural Sciences
  • University of Gothenburg
  • Swedish Rural Economy and Agricultural Society
  • Natural Resources Institute Finland (Luke)
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Agricultural Science
Original languageEnglish
Article numbere0177580
JournalPLoS ONE
Issue number5
Publication statusPublished - 2017 May 1
Publication categoryResearch