Ash dieback, which was first discovered in the UK in 2012, can cause ash trees to die prematurely.
Symptoms include dead branches, discoloured stems and blackened leaves, which can be seen hanging from infected trees in autumn
Diseased trees are more susceptible to a secondary infection called honey fungus, which damages root systems
The presence of both honey fungus and ash dieback can increase the risk of the three dying and becoming unstable.
A survey of 1,500 hectares of woodlands in Surrey by the SWT has revealed extensive areas of Ash trees already infected.
Over 80 dangerous or fallen ash trees have been removed from public footpaths and bridleways between April of last year and March 2018.
However, the SWT has announced today it will be felling ash trees in Norbury Park which stand within 30m of public footpaths, roads, bridleways and properties in November.
The work will be carried out using a forest harvester which fells the tree and takes the branches off mechanically.
Due to the extent of the disease it is too dangerous to use chainsaw operators for this work.
The decision comes after a review of the woodlands following guidance from the Forestry Commission and the National Tree Safety Group.
Ash trees beyond this range, with a lower risk to the public, will be left for nature to take its course, the SWT has said.
Ecological surveys have been carried out on all the areas identified for selective felling to check for the presence of protected species, such as bats, badgers and dormice.
James Adler, director of land management at Surrey Wildlife Trust, said: ‘We are devastated that we have to make this decision to fell infected Ash trees.
“But this disease is decimating our native Ash woodlands in front of our eyes. Public safety simply has to be our top priority whilst considering the most appropriate response.’
Matthew Woodcock, partnership and expertise manager at the Forestry Commission, said:
“We have visited several of the sites in Surrey, including Norbury Park, and can confirm there is a high penetration of ash dieback disease on these sites.
“Surrey Wildlife Trust has consulted with us and we support its decision to commence felling operations in the interests of visitor safety.”
Mr Adler added: “The sites will look different as the works will alter views from some pathways. But in time the woodlands will regenerate with a range of species including, hopefully, some disease tolerant Ash trees.
“There may be some silver linings for wildlife. Opening rides and glades will bring more light to the forest floor, so we may see more butterflies, orchids and other species benefiting.”