The Government has admitted eradicating ash dieback disease will now be impossible as it revealed some British trees have been infected for two years.
The admission came as the Department for the Environment unveiled a new action plan to tackle the outbreak, which is threatening the UK's native ash trees.
Some 129 sites are now confirmed be infected with Chalara fungus, known as ash dieback disease.
Fifteen of these are in nurseries, 50 in recently planted sites and 64 in the wider countryside.
Under the latest measures, affected new and young trees will be destroyed immediately and the search for the fungus will widen to include towns and cities.
However, burning contaminated mature trees has been ruled out because of fears about the damage to wildlife.
They also take longer to die and it is thought they could help experts learn more about genetic strains that could be resistant to the disease.
As part of the strategy, the public, along with foresters, land managers and environmental groups, will be told how to spot ash dieback and what to do if they find it.
The proposals to tackle the crisis, which threatens millions of the UK's native ash trees, were finalised by ministers at a Cobra crisis meeting.
Defra officials have worked with the Forestry Commission and other agencies to find the best way to contain the spread of the disease.
The importation of ash trees has already been banned and the planting of new ones halted.
Environment Secretary Owen Paterson admits it is impossible to wipe it out now that it has been found in mature trees but insists the British ash can still be saved.
"If we can slow its spread and minimise its impact, we will gain time to find those trees with genetic resistance to the disease and to restructure our woodlands to make them more resilient," he said.
"We now have a window of opportunity for action because the disease only spreads in the summer."
Ash dieback, which causes leaves to turn black and drop off before the whole tree eventually dies, is thought to have arrived in Britain on wind-borne spores blown in from mainland Europe.
Cases have been reported in Sussex, Berkshire, Lincolnshire, Yorkshire, Bedfordshire, Northumberland, Norfolk, Suffolk, Kent and Essex.
Other countries including France and Belgium have already been hit hard by the disease but Denmark has been the worst affected - losing 90% of its ash population.
There are fears the infection could have the same impact in Britain as the infamous Dutch Elm epidemic of the 1970s, which wiped out most of the country's elm trees.
There are an estimated 80 million ash trees in Britain - one-third of the entire tree population.
Several National Trust sites, including Ashridge in Hertfordshire, have put up signs as an extra precaution to prevent the disease spreading.
Ashridge Estate , a site popular with walkers that has been used in several films including Harry Potter And The Goblet Of Fire, has hundreds of ash trees in its 5,000 acres of woodland.
Estate manager Graeme Cannon told Sky News: "It's potentially very dangerous. Ashridge is here because ash trees feature very prominently in its background and they have done for hundreds, if not thousands, of years.
''With ash dieback in the country we'll end up in a situation where we will be losing a lot of our trees and they are an important feature of the British landscape and woodland.
"So far we have not had any confirmed cases in Ashridge but if we do then the impact would be catastrophic.''
Infected saplings are being burned but visitors to woods are also being asked to do their bit by keeping to marked paths to help reduce the spread of infected leaves.
They are also being advised to clean footwear and bike and car tyres of mud and earth when they get home.
Although the Government claims it has acted as swiftly as it could, there has been some criticism that the response has not been quick enough.