Tree disease

It is important that you take care when visiting forests and act appropriately to prevent the spread of tree disease.

Ash Dieback Disease

Ash Dieback is a disease of ash trees caused by the fungus Chalara fraxinea. The disease causes leaf loss and crown dieback in affected trees and can cause tree death.

Ash Dieback has been identified in young ash saplings at several sites in Northern Ireland. Read more information about this disease:

Phytophthora lateralis (P. lateralis)

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

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

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

Controlling 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 stay on the way marked paths.

Identifying Lawson cypress trees and P. lateralis

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

If landowners are concerned about the disease, they should send their name, address, telephone number and a photograph of the tree to:


Phytophthora ramorum (P. ramorum)

P. ramorum has the potential to cause serious damage to woodlands and plants in the wider environment.

Identifying Japanese larch trees and P. ramorum

The first indication of the disease on Japanese larch trees is a visible wilting of young shoots and foliage. Later in the growing season, signs of the disease include withered shoot tips with yellowing needles which then become blackened. The infected shoots shed their needles prematurely. Trees may also have bleeding cankers on their upper trunks.

All woodland owners and managers are asked to look out for symptoms of the disease in Japanese larch and report suspicious symptoms to Forest Service on the following number:

  • telephone: 028 9052 4480

Further information on the disease is available below:

Prevention of tree disease

Tree disease can be spread in many ways, including:

  • on footwear
  • on vehicle wheels
  • on tools and machinery
  • by the movement of infected plants
  • in rain, mists and air currents

If you’re visiting a forest, pay attention to signs showing what you should do to prevent the spread of tree disease.

In forests you should:

  • avoid any action which could move infected soil or plant parts to uninfected areas
  • stay on forest roads
  • keep dogs on leads
  • remove soil and mud from shoes and boots before leaving the woodland

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