By Barbara Brown, OPAL Community Scientist in South Wales
If you have ever recognised a face in a crowd when you are not searching, when you are thinking about that band, or the bus times… then suddenly, something in your subconscious flashes out “look there”... you will understand how a person can pick out the needle in the haystack which is one small sick tree in a wood.
The initial impression in my mind must have been made on July 24th, when I attended a Tree Health training course run by Alison Dyke of York University and organised by OPAL. The striking slides in her presentation on tree diseases were retrieved over three weeks later by that strange filing system which is memory.
This happened as I was almost running around the loop of footpath in a wood near Brecon, Powys, noting the best route for an OPAL tree workshop I was holding later on that day at the Biodiversity Information Service (BIS).
I was thinking about the length of the route, the tree species, the slope of the path and the presence of a hand-rail when all of a sudden I stopped dead.
There was an Ash sapling next to the hand-rail with drooping leaves and it matched a picture in my mind’s eye. On walking over I saw that the slender trunk was marked with large, dark diamond-shaped scars around the forks of the side-branches.
These are typical of an Ash tree infected with Hymenoscyphus fraxineus – the fungus that causes Chalara or Ash Dieback.
From Bucks to Brecon
Ash Dieback was first found in the UK in 2012 on imported trees in a plant nursery in Buckinghamshire. This outbreak was controlled, but in October 2012 some cases were reported in Norfolk and Suffolk, which appear to have been spread by wind-blown fungal spores.
In 2013 an isolated case was found in Carmarthenshire, Wales, and now other affected trees are being found.
I felt sad coming back to the BIS office through the gleaming green wood. The tree would have to be reported and, if the disease was confirmed, other Ash trees nearby might soon be infected. There is however some hope of slowing the spread of the Ash Dieback in the UK.
Reporting any occurrence is an important part of the strategy for this.
Leading the resistance
Forest Research (part of the Forestry Commission) is leading a mass screening trial of Ash trees to identify resistance to Ash Dieback. They are planting large stands of Ash with different genetic profiles to see which are most resistant to the spores of the Chalara fungus. Experience from Europe shows that not all trees die of infection and that a small fraction survive and pass this ability to their offspring.
If you do come across a tree that you think has Ash Dieback please report it to Tree Alert on the Forestry Commission’s website. You can also ring the Chalara helpline: 08459 335577.