Forestry Commission logo

Phytophthora - tree destroyers

Phytophthoras are a large goup of pathogens which cause diseases in plants, including many species of tree. The name is derived from Greek and literally means 'plant destroyer' from phyto (plant) and phthora (destroyer).

Following is a summary of the most significant phytophthora threats to the UK's trees, woods and forests, with links to further information about each one.

Phytophthora alni

Phytophthora alni is highly specific to alder trees, species commonly found on riverbanks thanks to their preference for cool, damp sites. It was first identified in Britain in 1993, and has been the cause of thousands of alder tree deaths throughout Great Britain.

Phytophthora austrocedri

Phytophthora austrocedri is a rare form of phytophthora which was confirmed in 2011 by Forest Research scientists as the cause of dieback and mortality in juniper bushes in the Moor House - Upper Teesdale Natural Nature Reserve in the North Pennines of England. It had previously mostly only been associated with decline of Chilean cedars (Austrocedrus chilensis) in the Patagonia region of Chile and Argentina.

Phytophthora kernoviae

Phytophthora kernoviae is a recent discovery which so far has only been found in Britain, Ireland and New Zealand. It has been found to cause damage to some tree species, including beech and pedunculate or 'English' oak (Quercus robur), although so far it has affected very few trees in Britain.

Phytophthora lateralis

Phytophthora lateralis  particularly affects Lawson cypress trees (Chamaecyparis lawsoniana), and kills most of those that it infects. It is the main cause of deaths in Lawson cypress in its native range in south-western Oregon and north-western California. It was first identified in Great Britain in 2010. 

Phytophthora ramorum

Phytophthora ramorum can cause extensive damage and mortality to a wide range of trees and plants including, in Great Britain, woodland plants such as larch, rhododendron and bilberry.

Phytophthora films

Videos - the threat to trees, woods and forest plants from Phytophthora ramorum and Phytophthora kernoviae and how their spread can be prevented


Further reading


Last updated: 9th May 2018