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Home » Looking After » Conservation Land Management » Woodland Management » Tree Diseases

Tree Diseases

Since 2009 two serious tree diseases of larch and ash have been affecting sites in the UK and beyond.  Whilst larch has economic consequences for timber growers, ash is a significant native tree and there is a real risk that it could disappear from the countryside as happened in the 1970s with Dutch elm disease.

Chalara fraxinea, more commonly known as ash dieback is a fungal disease specific to ash. It is dispersed by wind borne spores and has already devastated trees in Denmark and elsewhere on the continent.

Ash dieback was confirmed on planted sites in the UK in 2012 where trees were imported from infected areas in Europe and has already spread into the wider environment at a few locations, including one at Ferryside in Wales.

It is hoped the early detection and removal of infected young trees can slow down the loss of ash trees and woodland which account for as much as 14% of our woodland resource in Wales, maybe be more in Pembrokeshire. There is also hope that some trees may be more resistant to the disease.

Phytophthora ramorum is another fungal disease spread by both water and in the air that can affect a variety of plants. Its main hosts are rhododendron and larch but it can also attack other tree species as well as garden plants such as viburnum and magnolia and heathland plants such as bilberry.

It was first identified in Wales in 2009 and with large areas of larch affected in South and West Wales. Pembrokeshire Coast National Park Authority felled around 400 infected larch trees in June 2013.

What can you do to help?

1. Follow simple biosecurity measures

If you live in or are visiting an area where a tree disease has been confirmed, following simple biosecurity measures such as those set out below will help limit the spread.

  • Respect closure signs – the National Park Authority may close paths around affected sites to limit footfall in the infected area.
  • Clean footwear and clothing – brushing off mud and debris.
  • Leave all plant material on site – this will help limit the spread.
  • Ensure dogs are cleaned between walks – this will help limit the spread of spores.

2. Report sightings of infected trees

Symptoms are shown in the videos linked below.


If you are concerned about trees you have seen, you can report your findings (note locations and take photographs) using the following links:

Related links: