Walkers heading for woodland in the Dales should clean their boots afterwards

Outdoor enthusiasts visiting a national park are being urged to wash their boots and bike wheels after passing through woodland.

The Yorkshire Dales National Park Authority issued the plea in an effort to protect its ash trees from the deadly fungal disease threatening Britain’s woodland.

People should also avoid visiting similar areas within 24 hours if they have ventured into woodland in the national park, one of its conservation experts said.

Ash dieback disease has been discovered at various sites across Britain and is caused by the fungus Chalara fraxinea, spread by insects, the wind and rain splashes.

It causes leaf loss and kills off the tree’s crown, often resulting in the death of the ash tree.

The character of the area will be changed radically if the disease takes hold, the national park authority said.

National park conservation experts are working closely with the Forestry Commission – which is leading the effort to contain the disease – and are currently surveying woodlands containing ash trees to see if there are any symptoms.

Geoff Garrett, the YDNPA’s senior trees and woodland officer, said: “Ash is such an important tree in the broadleaved woodlands of the limestone uplands of the Yorkshire Dales that we are treating the potential impact of the disease very seriously.

“It is impossible to say with any accuracy how many well established ash trees we have in the national park but it’s in the order of hundreds of thousands – perhaps even millions.

“On top of that, we have planted about 250,000 new ones in the last 10 years, and they are all at risk from this disease.

“So far we have found no symptoms of it but we would ask people to take extra care when they are out enjoying this beautiful place.

“If they have to go into an area full of trees, we would ask them not to visit other similar areas within a 24-hour period and to make sure they clean their boots, car and bicycle tyres, dogs and anything else that may have come into contact with leaves or wood.

“If the disease were to take hold in the national park, it would irreversibly alter the character of our woodlands which in turn would have a dramatic effect on the landscape, altering it forever.”

Information on ash dieback is available from the Forestry Commission’s Forest Research Tree Health Diagnostic and Advisory Service on 01420 23000 or on its website. http://www.forestry.gov.uk/forestry/infd-8w9euv