Skip to main content

Pests and diseases

The threat to our forests

Given the long lives of trees, it can be surprising to learn that many trees in Scotland are at risk from pests and diseases. Whilst some trees can live for centuries, some infections can cause them to deteriorate and die within a few weeks.

We look after a large proportion of Scotland’s forests. Therefore our work to prevent and slow the spread of infections is crucial in keeping our national forests and habitats in good health. 

Surveying for pests and disease 

It’s vital to monitor the health of our forests for diseases and invasive pests. Left unchecked, these threats can cause widespread tree deaths. This can lead to several serious issues: 

  • large changes in habitats affecting biodiversity and wildlife
  • unstable deadwood that can, in some cases, pose a risk to buildings and nearby infrastructure
  • a loss of useful timber, and the associated carbon storage
  • landscape and forest design issues

How we monitor these threats

Late spring and summer is and important time to assess forests for infected trees. As leaves bloom, those trees that are suffering are recognisable by their reduced canopies or discoloured leaves. Surveys for controlled pests and diseases such as P. ramorum are carried out by the forestry regulator, Scottish Forestry. Through ground surveys and helicopter flights, much of our land is assessed ready for vital works to be carried out later in the year.

We look for signs of sick trees in our forests and report any suspected pests and diseases to Scottish Forestry. By taking action quickly, we can slow or stop the spread of pests and diseases. Given the amount of land we manage, we have a vital role in keeping Scotland’s trees healthy. 

Members of the public can also report pests and diseases through Tree Alert.

What this means for the future of Scotland’s forests

We have been dealing with tree diseases such as P. ramorum in Scotland for over a decade. We actively monitor the risks in hope of slowing the spread while working to restore the land.

As the climate changes, we expect new diseases and pests (such as the recent discovery of Phytophthora pluvialis in 2021) to threaten our forests and land. Warmer temperatures can give some pests and diseases a helping hand to move into areas that were previously too cold for them to survive. To prepare for and combat these threats, we are adapting our work to create forests that are better able to stand up to an uncertain future by: 

  • Planting forests with a greater mix of tree species. By managing diverse forests and woods, we can reduce the chance of a single disease or pest wiping out large areas.
  • Growing our own saplings in Scotland, or sourcing from within the UK, to avoid importing pests.
  • Actively removing invasive non-native species which threaten our forests.
  • Running trials to find tree species that might be resistant to certain diseases.

Man and woman stroll together through Kilmun Arboretum

Kilmun Arboretum tree trial

We are currently running a trial in Dunoon to see what species of trees will grow well in Scotland.  

Kilmun Arboretum is one of three national arboretums in the UK. It was established in the 1930s as a living laboratory where experts tested to see what species of trees could grow in our climate. Over 260 tree species were planted there in small plots. Of those, over 200 thrived making Kilmun an important site for forestry in Britain.  

We are now using this initial research to solve the modern problem of replacing the thousands of trees being lost to tree disease across Scotland.

Learn more about the trial at Kilmun


How you can help protect Scotland's trees

There are no simple cures for many of the diseases and pests threatening our forests. Stopping the spread and taking action before they get out of hand is the best defence we have. That’s why we ask all visitors to our forests and land to Keep It Clean.

Before going to a forest, make sure your boots and bikes are free of dirt and debris. This simple action can cut down the chances of diseases spreading from one forest to another. You can also report sightings of pests and diseases through Tree Alert.

Find out more