Phytophthora austrocedri

Phytophthora diseases are caused by a genus of fungus-like pathogens known as water moulds. 

Phytophthora austrocedri is an aggressive pathogen of juniper and cypress trees, causing root and stem infections, dieback and often mortality of affected trees. Its origin is unknown, but it has likely been introduced to the UK and Argentina, where it is affecting native cypress trees. The disease was first confirmed in the UK in 2011 by Forest Research, who had been studying dieback in juniper trees. It has to date mainly been found in Scotland and Northern England, there have been no confirmed reports for Wales or Northern Ireland. 

This disease is a particular problem for Juniper, one of only three native conifer species in the UK. There are only a small number of Juniper woodlands remaining, many of which are protected. In Scotland, significant outbreaks of Phytophthora austrocedri have occurred in the Cairngorms National Park and Glen Artney, Perthshire. In England, the disease has been found in the second largest population of juniper at the Upper Teesdale National Nature Reserve.  

The pathogen primarily attacks the trees’ roots but can cause lesions at the root collar which can girdle the tree and progress up the stem. Occasionally, infections of aerial branches have been recorded. Symptoms include bronzing or browning of the canopy and dieback, which can often be associated, associated with underbark lesions. These lesions are not visible unless the bark is removed.  

For more information about Phytophthora austrocedri, see the resources below.