Phytophthora lateralis

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

Phytophthora lateralis is a pathogen that mainly affects Lawson cypress trees, although it can also affect western red cedar, Sawara cypress, Pacific yew and juniper. This Phytophthora is thought to originate in Asia, and has been introduced to the USA, where it has had a severe impact in native forests, as well as to mainland Europe and the UK. It was first detected in the UK in 2010, having most likely arrived through the importation of infected plants. It has been found in all four countries in the UK but tends to be found more in Scotland and Northern Ireland. 

The pathogen primarily attacks the trees’ roots and causes lesions at the root collar which can girdle trees 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 with lesions beneath the bark. The lesions are not visible unless the bark is removed. 

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