What is it?
Chalara dieback of ash is a serious disease of ash trees caused by a fungus called Chalara fraxinea.
Symptoms of the disease include leaf wilt and loss, twig and branch dieback, bark lesions and timber staining, and usually lead to the death of the tree. There is no antidote or preventative treatment.
Infected dead leaf stalks are shed during autumn, and produce spores from fruit bodies which form on the dead leaves during the following summer, infecting new leaves between June and September.
The disease becomes obvious in young trees, within months rather than years, but it's not clear how quickly mature trees will die to the point of losing limbs.
A very low percentage (probably 1-2%) of common ash (fraxinus excelsior) is likely to have genetic resistance.
Will it affect us?
Ash dieback is spreading rapidly through the UK aided by the fungal spores being windborn. As well as various places in the western Yorkshire Dales, it has now been confirmed in Ingleton and on the A65 in Kirkby Lonsdale. This means it is almost inevitable that Casterton will be infected sooner or later.
What should we do?
Movement of ash plants and seeds are forbidden within the UK, but there is no restriction on the movement of ashwood, including firewood, unless a statutory Plant Health Notice has been issued.
You should keep an eye on infected trees you own in case pruning is required for safety reasons.
Most importantly you can help to slow the spread of Ash Dieback, by adopting simple biosecurity measures. For leisure walkers this means thoroughly cleaning boots if you have been walking in an area known to be infected, and if possible drying them (the spores can only survive for 48 hours without moisture). If Casterton does have the disease, then clean your boots thoroughly, and if possible dry them, before walking in another area like the Howgills or the Lake District, where you might otherwise introduce the disease. Brush off footwear and clothes before leaving woodland. The same rules apply to any equipment which may have been used.
Professionals such as forestry workers are encouraged to take further measures such as cleaning tools and vehicle wheels and wheelarches, and avoiding driving offroad wherever possible. There are recommended anti-bacterial sprays which are effective.
There is a great deal of further information on the Forestry Commission Website, www.forestrygov.uk, where you can also report new cases of the disease.
Latest News, October 2017
We were invited by YDNPA to take part in the 'Living Ash' project, designed to generate data for the scientific community on the progress of the disease. A healthy ash tree in the village has been labelled with a numbered aluminium tag, and the condition of the tree will be examined from time to time, and the data and photographs sent back to the project.