Pests and diseases

The threat to our forests

Healthy trees can live for decades or even centuries, but did you know that many trees in Scotland are at risk from pests and diseases. These infections can even cause them to deteriorate and die within a few weeks.

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

Find out more about some of the threats below:

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 trees - this could 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 an important time to assess forests for infected trees. During this time leaves bloom - this means we can see discoloured leaves. Another sign trees are suffering is their reduced canopies. The canopy is the upper layer of a tree where leaves extend from the branches.

Scottish Forestry (the forestry regulator) surveys for controlled pests and diseases like Phytophthora ramorum. The ground surveys and helicopter flights carried out help to plan vital felling that we will do later in the year.

We also look for signs of sick trees in our forests. Any suspected pests and diseases are then reported to Scottish Forestry. By taking prompt action, we can slow or stop the spread.

Members of the public can also report pests and diseases they spot. Tree Alert is an online reporting tool where sightings can be reported.

What this means for the future of Scotland’s forests

As the climate changes, we expect new diseases and pests to threaten our forests and land. Warmer temperatures can give some pests and diseases a helping hand. They can move into areas that used to be too cold for them to survive and the warmer temperatures lead to more opportunities for the threats breeding and spreading.

To prepare for and combat these threats, we are adapting our work. We will create and look after forests that are better able to stand up to an uncertain future by:

planting forests with a greater mix of tree species. Diverse forests and woods 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

Kilmun Arboretum tree trial

We are currently running a trial in Dunoon to see what species of trees grow well in Scotland as well as looking into what species will thrive in the future.

Kilmun Arboretum is one of three national arboretums in the UK. Arboretums are botanical gardens specialising in trees and shrubs. Established in the 1930s as a living laboratory, it was created so forestry experts could test to see what species of trees could grow in our climate. Over 260 tree species were planted in the arboretum in small plots. Of those, over 200 thrived making Kilmun an important site for forestry research in the UK.

We use this research to solve the modern problem of replacing the thousands of trees lost to tree disease across Scotland.

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.