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8 Dec 2020

Looking out for Scotland’s trees

Written by Ann Steele, Head of Heritage Gardening (Policy)
In wintertime, when they have no leaves, ash trees can be identified by the very dark and pointed buds on their twigs.
Want to identify an ash tree in winter? Look for its sooty buds
With increasing numbers of pests and diseases threatening to affect Scottish trees, the National Trust for Scotland has teamed up with citizen science group Observatree to help spot problems early.

Tree pests and diseases don’t see borders. They’re happy to hitch a lift across the world on plant material, timber products – or even on people’s clothing or shoes! Knowing how important Scotland’s trees are to our landscapes, to biodiversity and to future mitigation of climate change, we’ve teamed up with citizen science group Observatree to help spot new tree pest and disease problems quickly.

One tree disease you may already have heard about is ash dieback. You’ll certainly be hearing a lot more about it in future as experts are seeing it spreading across Scotland. Ash dieback is likely to kill many young and mature ash trees over the next few years. Symptoms can include leaf and shoot dieback, and a diamond-shaped lesion where a branch meets the trunk. It’s not treatable, so to give Scotland’s ash population the best chance to survive and thrive again, management efforts are now focused on mitigating safety risks from diseased trees, while allowing for natural regeneration of potentially disease-tolerant or resistant trees wherever possible. By joining forces with Observatree, the Trust will be better able to monitor the spread of ash dieback and help inform national decisions on responding to the disease. This will ensure that Scotland’s ash population can be enjoyed by future generations in parks, gardens and wider landscapes.

Tree trunk with a long, diamond-shaped lesion, which is indicative of ash dieback disease.
The long diamond-shaped lesion or scar where the branch meets the trunk on this young ash tree is a symptom ash dieback disease (image supplied by Dr David Slawson)

Ash dieback is just one of a number of pest and disease concerns at the moment and Observatree has worked with UK plant health authorities to identify those that are most worrying. Their volunteers are trained to recognise the symptoms of attack from a focused range of problem pests and diseases, and to report them to Forest Research (the Forestry Commission’s research agency) through TreeAlert. Attention is on those pests and diseases most likely to arrive in the UK, those that have already arrived and are causing concern about their spread, and those that have the potential to cause the most serious and widespread impact on commercial forestry, amenity woodland and ecological systems.

The earlier an outbreak is spotted, the greater the chance that a pest or disease can be stopped in its tracks, or that its spread can be slowed down. Our staff and volunteers who work with gardens and wider landscapes are very knowledgeable in these areas already, of course, but the more trained eyes we have helping us to look, the better!

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