Impact of Phytophthora diseases on trees


PhotoThe Phytophthora research programme focussed on assessing the impact of various Phytophthora species, including newly arrived species such as P. ramorum and P. kernoviae (first discovered affecting trees in the UK in 2003) and the more recently discovered P. lateralis. In addition, established Phytophthora species showing changed behaviour, perhaps due to climate change or exposure to new hosts, were also under investigation.

Phytophthora (Greek for ‘plant destroyer’) is one of the world’s most destructive genera of plant pathogens.  Probably the most famous species of the genus in Phytophthora infestans, which attacks the leaves and stems of potato plants and causes the disease that contributed to the potato famine in Ireland in the mid 1800s. Since the early 1990’s the profile of Phytophthoras in forests and natural ecosystems has risen markedly around the globe and diseasessuch as Phytophthora disease of alder and Sudden Oak Death are widespread and highly damaging in some countries.Photo 

Research objectives

  • Effective diagnosis and detection of Phytophthora pathogens which affect trees.
  • Understand the distribution and the impact of recently introduced Phytophthoras, such as Phytophthora ramorum, P. kernoviae and P. lateralis, to trees in Britain.
  • Assess the susceptibility of forest and woodland tree species to P. ramorum and P. kernoviae to gauge the potential risk these pathogens pose to our trees and environment and inform future planting recommendations.
  • Analyse the extent of variation in some of the recently arrived Phytophthora species to identify the possible origins, entry pathways and potential for genetic change.
  • Obtain field data on the infection process and disease development in relation to key variables (e.g. host availability, inoculum production and climate).
  • Determine how Phytophthora pathogens spread in natural and semi-natural environments.
  • Through increased understanding of the biology of Phytophthora pathogens, provide effective advice to aid management decisions on management, containment and eradication.

Pest risk analysis (PRA)

The European PRA of P. ramorum is now available.

Further information

Forestry Commission publications

Further information on Phytophthora diseases can be found in various Forestry Commission publications including:

Forestry Commission pest and diseases pages

These include frequently asked questions (FAQs).

Presentation to Royal Institution of Chartered Surveyors in March 2011

Current tree health issues (PDF-1375K)
Acute oak decline, Phytophthora diseases and Dothistroma needle blight.

Funders and partners

Forestry Commission logo Defra logo USDA Forest Service logo EU flag
This research is funded by the Forestry Commission as part of the Phytophthora Diseases Work Area (part of the Advice and Scientific Support for Tree Health Programme), Defra, the USDA Forest Service and through various EU initiatives including FP6 & 7 Projects and COST Actions.


Work on Phytophthora diseases of trees has been a key part of the work of Forest Research for many years. Research on Phytophthora ramorum and P. kernoviae started in 2003 and was extended in 2011 to include other damaging Phytophthoras such as P. lateralis, P. pseudosyringae and P. cinnamomi as part of the Advice and Scientific Support for Tree Health programme.


Dr Joan Webber