The 144 ash trees on the Ashridge Estate are at risk of catching a deadly disease that is spreading across the UK, manager have confirmed.
Ash dieback was first reported in this country in February when it was found in a batch of trees sent from the Netherlands to a nursery in Bucks.
By that point, it had already devastated 90 per cent of the ash trees in Denmark and spread to countries across mainland Europe.
National Trust property manager Graeme Cannon said: “It would be devastating if our worst fears are realised and we lost our ash trees.”
Ash is the fifth most populous species of tree on the estate.
Mr Cannon said: “They are remarkable trees – 200 to 300 years old and a very important part of the eco-system.
“If they were to go, it would have a devastating impact on the estate and change the landscape at Ashridge.”
Ash dieback starts in the spores of ash tree leaves, making them particularly vulnerable in autumn when their leaves fall off trees and get blown around, spreading the disease.
The most at-risk areas are places that have received young ash plants from nurseries in the last five years.
But last month, the disease was found in large, natural woodlands in East Anglia.
This raises the prospect of the disease arriving at Ashridge and other important nature sites.
Hundreds of staff from government agencies have been checking ash trees across the UK for signs of the disease since early November.
Although none have been found in Ashridge, Mr Cannon said: “We will not really know the full scale of the impact of the disease until spring.”
The first sign of the disease, caused by the Chalara fraxinea fungus, is loss of leaves on the ash trees, as it cannot grow them back.
The crown of the tree then dies back, leading to their death, which can take ages for mature trees.
Walkers are advised to stick to paths and not let their dogs off leads in the estate to prevent the spread of the disease.
Cleaning your shoes after leaving sites where there are ash trees will also help stop it spreading.