Phytophthora ramorum (P. ramorum) is a fungus-like pathogen of plants that is causing extensive damage and mortality to trees and other plants in parts of the United Kingdom. It has also been found in a number of European countries, but mostly on plants and shrubs, especially rhododendron, viburnum and camellia, and has caused significant damage and mortality to many trees and other plants in parts of the USA.
However, few trees in the UK were affected until 2009, when P. ramorum was found infecting and killing large numbers of Japanese larch trees in South West England. Then in 2010 it was found on Japanese larches in Wales, Northern Ireland and the Republic of Ireland, and 2011 it was confirmed at locations in western Scotland.
This sudden change in the pathogen’s behaviour was the first time in the world that P. ramorum had infected and sporulated (reproduced) on large numbers of a commercially important conifer tree species. It was also an unexpected setback to efforts to tackle ramorum disease.
We and our partners have moved quickly to respond to this development. Full details about the pathogen and what’s being done to research it, minimise its impact, and support affected woodland owners are available at the links on this page.
Among the key documents and guidance available within these pages are:
Symptoms guide. Larch can suffer from a number of diseases, not all all of them serious, so before reporting a suspected case, check the symptoms of ramorum disease in our symptoms guide.
Replanting advice. We do not recommend restocking (replanting) affected sites with larch or other species that are susceptible to P. ramorum, so this guide sets out options for the woodland owner.
Biosecurity precautions. This guide provides advice on precautions to take when visiting or working in an infected woodland to limit the risk of accidentally spreading the disease on clothes, tools or vehicles etc. See also our more generic Biosecurity Guidance document.
P. ramorum found on Sitka spruce
The Forest Service of the Irish Department of Agriculture, Fisheries & Food has reported the first finding of a Sitka spruce (Picea sitchensis) in the wild infected with Phytophthora ramorum. Sitka spruce is the most widely grown timber-producing tree species in the United Kingdom. For further information see the section on P. ramorum on Sitka spruce in the update report.
Plant health inspections
Inspections of trees and woodland by Forestry Commission plant health inspectors play an important role in our efforts to manage outbreaks of ramorum disease. Guidance for Plant Health Inspectors can help you understand what to expect if an inspector needs to visit your premises.