Phytophthora Lateralis

Phytophthora lateralis (P. Lateralis) infects tree roots which come into contact with spores in the soil or water, and it kills most Lawson cypress trees it infects.

Public forests affected

P. lateralis is present in a number of locations, including:

  • Tollymore Forest
  • Mourne Forest
  • Somerset Forest

A very small number of affected trees have also been identified in Castlewellan and Belvoir Forests.

The implementation of measures to control the spread of P. lateralis is ongoing. Public access to certain areas of these forests is restricted to prevent soil movement, and users of the forests are asked to observe signage and remain on the way marked paths.

How can I identify Lawson cypress trees and P. lateralis?

Anyone concerned about Lawson cypress trees are asked to access the guide below where information on the identification of Lawson cypress and P. lateralis symptoms is available.

If land owners are concerned about symptoms in trees or plants they should send an email with their name, address, contact details, and a photograph of the tree to You can also report suspect symptoms using a smartphone. Go to and complete the form.

Further information

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