THOUSANDS of trees are to be felled on the Holnicote Estate on Exmoor to prevent a deadly fungus spreading.

The outbreak was discovered by rangers on the estate a few weeks ago and confirmed by the Forestry Commission.

The fungus Phytophthora ramorum – also known as sudden larch death – is affecting larch trees on the National Trust estate.

Ian Wright, the trust’s expert on the fungus, said: “The spread of Phytophthora into woodlands is a real concern as it represents a significant and worrying development for a disease which has up to now been predominately garden-focused.

“For the trust, monitoring presents a challenge as larch is growing over extensive areas at trust sites throughout the UK.”

Mark Courtiour, the trust’s Somerset countryside manager, said: “A total of 30 hectares of land, mostly commercially planted, will be cleared.”

At Holnicote Estate, about 20 hectares will be cleared and a further ten acres on the Quantock Hills.

A Forestry Commission report describes the fungus as “aggressive” and “unpredictable” with devastating effects for larch plantations, which it says are an important timber tree in western Britain.

The report by forest researchers Clive Bra-sier and Joan Webber said: “Damaging invasions of tree pathogens are not new, as earlier pandemics of Dutch elm disease and chestnut blight have shown.

“But these events appear to be accelerating due to the combined effects of increasing globalisation of trade in plants and a flaw in international plant biosecurity protocols.

“In 2003 it was found to be infecting woodland trees in South-West England and the Netherlands.

“But, until now, tree infections have been comparatively rare and limited.”