A BAN on the import of ash trees to combat the threat of ash dieback could be too late to stop the disease spreading across the UK.

Experts fear the disease is the biggest threat to the British countryside since Dutch elm disease saw millions of trees felled 30 years ago.

Caused by the fungus Chalara fraxinea, ash dieback leads to leaf loss and has already affected trees in England and Scotland, and killed trees in parts of mainland Europe.

The government said a rapid eight-week consultation showed there was strong support for the import ban, which came into effect last Monday (29 October)

Movement restrictions have also been imposed, so that trees from infected areas will not be able to be moved to other locations within the UK.

"This is a very serious disease that demands action to stop its spread," said Defra secretary Owen Paterson. "I have ordered both an import ban and movement restrictions on trees from infected areas."

"This comes into force immediately."

Plant Health Authorities have been monitoring trees in infected areas to ensure early detection and trade bodies have been encouraging their members to impose voluntary import bans.

The government said authorities would remain on high alert across the country and continue to look for signs of Chalara, ensuring infected trees were dealt with effectively.

But the Woodland Trust said urgent and clear advice to all woodland owners was needed so the disease could be managed and wider issues surrounding tree diseases addressed.

The import ban was prompted by the discovery of ash dieback at a Woodland Trust site Pound Farm, near Great Glenham in Suffolk.

The site was purchased by the trust in 1992 and is around 90ha in size. It is a mix of new native plantings and existing ancient woodland.

Previously, ash dieback had been confined to imported trees at nurseries. But the Woodland Trust site had no obvious connection with imports.

Trust chief executive Sue Holden said: "We are clearly pleased to see Owen Paterson finally taking action to introduce a ban on the import and movement of ash trees in to the UK.

"We also ask government scientists to give urgent and clear advice to all woodland owners on how to manage the disease.

The trust would do all it could to mitigate spread of ash dieback in line with the government's instruction and advice. But it was only one of numerous tree pests and diseases in the UK.

With more than 15 separate pests and diseases listed on the Forestry Commission website as already present, it was crucial that the wider issue is tackled."

"This situation is symptomatic of the lack of priority given to the protection and safeguarding of our natural woodland resources.

"We need to make woodland and the environment a priority and create a political and economic environment that will enable the sustainability of vibrant woodland habitats across the UK."

Suspected cases of ash dieback should be reported to the Forestry Commission or the Food and Environment Research Agency so action can be taken to prevent the disease from spreading.