Ash trees in Hainault Forest are being monitored for a vicious tree disease that has already nearly wiped out a common species of the tree in several European countries.

Trees are being killed by the fungus Chalara fraxinea, which starts with small spots, leading to lesions on stems and branches, leaves wilting, branches dying and the death of the top of the tree.

The disease can kill young trees quickly but older trees can survive for longer.

Ash trees are common in Hainault Forest, especially around Roe’s Well and Sheepwater.

The tree is common in parks and roads across the country and makes up an estimated five per cent of UK woodland.

Imports of the trees have been banned and infected saplings and young trees at nurseries and planting sites are being destroyed.

In infected areas of established trees, movement restrictions are being imposed so the disease cannot spread.

A Foresty Commission spokesman said landowners are issued with a notice to destroy infected trees where they are found and biological controls, such as washing people’s shoes on entering and leaving woods, could be introduced.