Phythopthora austrocedri – juniper dieback and mortality

Disease overview

Juniper bush with dieback caused by Phytophthora austrocedrae at Upper Teesdale National Nature Reserve in Northern England        The aggressive fungus-like pathogen is infecting juniper at a large number of upland woodland sites in northern Britain and causing dieback and mortality.

P. austrocedri was first described in 2007 in southern Argentina where it is killing trees of the native South American conifer species, Austrocedrus chilensis. Since then, the pathogen has also been found infecting individual amenity specimens of Lawson cypress (Chamaecyparis lawsoniana) and Nootka Cypress (Chamaecyparis nootkatensis) in Scotland. Reported hosts are all members of the cypress family (Cupressaceae).

This resource will help you to identify P. austrocedri infections and submit samples for diagnosis.


PHYTOPHTHORA . Typical symptoms of Phytophthora root and stem base killing on Juniperus communis suecica which has been  raised in a container . Location: Solihull , West Midlands , England .P. austrocedri primarily attacks juniper roots, branches and stem bases; the pathogen can extend 50cm or more up diseased stems.

  • Reddened and browning foliage over all or most of the crown
  • Scattered dieback of shoots or individual branches
  • Phloem (inner bark) turns from a healthy white to orange-brown
  • Phloem may display a diffuse yellow concentration in advance of forming an infection lesion
  • Phloem sometimes has resin pockets

To examine the phloem, cut away the outer bark from the base of the tree. If you suspect P. austrocderi in a tree, our Tree Health and Diagnostic Advisory Service can confirm infection. Please get in touch.

Our Research

Forest Research is involved in projects to study Phytophthora infections in UK trees:

  • Impact of Phytophthora diseases on trees
  • Phytophthora disease of alder
  • Phytophthora kernoviae

Related resources


Dr. Sarah Green