This disease was first recorded in the UK in 2012 and is now widespread throughout Scotland. Scottish Forestry estimates we will lose up to 50-75% of all ash trees in the country in the next twenty years.
The fungus attacks the leaves and stem, eventually infiltrating the tree and blocking the movement of water through the trunk. This causes the tree to produce less foliage and ‘die back’.
Ash trees with this disease can sometimes die within a few years, although others can survive for much longer. The dead ash stand out in the canopy as they’ll eventually become brittle and drop their leaves and smaller branches, losing a lot of the flowing characteristics of a healthy ash tree.
Because the disease is so widespread across the country, we are now focusing on the safety risks rather than ongoing surveys and specific biosecurity measures. If trees become brittle, this can create a health and safety risk due to the possibility of branches or trees falling. In these cases, they need to be managed carefully and sometimes removed, especially near paths, roads, or buildings.
We are currently not planting new ash but allowing natural regeneration of ash in native woodlands to help encourage resistant ash genotypes to grow. This is done with the help of deer control to protect the new trees.
Ash dieback and Scotland’s rainforest
Ash is an important native tree that supports biodiversity and is home to a range of rare moss and lichen species key to our rainforest habitats along the West coast of Scotland. This is because the bark chemistry of the ash tree is quite rich and a favourite of certain species of lichen. Trees with similar bark chemistry include hazel, willows and rowan, all of which are also favourites for deer making it really difficult to establish alternative species to replace the diseased ash trees.
Learn more about Scotland's rainforest
New life to diseased trees
Some of the infected ash trees can be given new life and sold as timber. This depends on how quickly they’re assessed to have the disease and how quickly we can remove them. Also we don’t always want to remove diseased trees too soon because they can recover from the disease – it’s a balance! Diseased trees are extremely dangerous to bring down and careful planning and special equipment may be required.
Recently we processed a 25-metre ash tree using an Alaskan mill for a furniture maker in South Scotland. This tree will be used to create various household fixtures.