Ministers are set to publish an action plan outlining how it plans to tackle ash dieback, which is threatening the UK's 80 million ash trees.
Survey results on Wednesday confirmed that the disease was present at 115 sites in England, Wales and Scotland.
The findings showed that 15 nurseries, 39 planting sites and 61 locations in the wider environment were infected.
Environment Secretary Owen Paterson will chair another emergency meeting on Friday to discuss the action plan.
A ban on ash imports and the movement of trees from areas with confirmed cases of dieback came into force on 29 October, just days after government scientists confirmed that the disease had reached the UK's natural environment - at sites in East Anglia.
"I think it is clear that we are not going to be able to eradicate this disease," Martin Ward, Defra's chief plant health officer, told BBC News on Wednesday after a summit of "key stakeholders" to discuss the arrival of the disease in the UK.
He added that data gathered by scientists in Demark, where an estimated 90% of the nation's ash trees were infected, ash dieback can spread by about 20km (12 miles) each year.
"One of the things we were asking for today was for ways in which we can slow down that spread while we look for pockets of resistance," he said.
"One of the positive things we know from the continent is that ash is a very diverse species and there is a small proportion of trees that are likely to have a natural resistance and could be found and propagated."
Hilary Allison, policy director for the Woodland Trust, attended the meeting and said the survey's results suggested that the outlook for the UK's ash trees looked bleak.
Continue reading the main storyEcology of ash trees
Known as the common or European ash, the tree - the UK's only native ash species - is scientifically known as Fraxinus excelsior.
It is the UK's third most abundant species of broadleaved tree (after oak and birch), covering 129,000 hectares of woodland.
Ash is deemed to be a very important species within the UK's hedgerows and accounts for about for about 10% of the nation's estimated 123 million "non-woodland" trees.
The common ash is a large deciduous tree that can reach heights in excess of 40 metres (130ft). It can live up to 400 years but coppiced trees can live for centuries longer. The species is wind-pollinated, and the seeds (known as keys) are primarily dispersed by the wind.
As the species is long-lived, it is important for wildlife. It supports specialist deadwood species such as the lesser stag beetle and hole-nesting birds including owls and woodpeckers.
Ash woodlands have light, open canopies, so are an important habitat for flora such as bluebells and ramsons. Birds such as bullfinches feed on the trees' seeds.
Also, ash provides an important habitat for more than a quarter of Britain's lichen, including nearly 14% of the nationally rare/scarce species.
Upland mixed ash woodlands are listed as a priority habitat under the UK Biodiversity Action Plan.
"I think this shows that it is increasingly serious for ash trees," she told BBC News.
"It is not looking good as [dieback] is out in the wider countryside and whether we can contain the spread is really doubtful.
"I think we are now in a situation of managing ash dieback. It is about good advice to land owners and good advice to members of the public."
Dieback, caused by the Chalara fraxinea fungus, was first recorded in eastern Europe in 1992 and spread over two decades to infect most of the continent.
The first confirmed cases in UK woodlands were at sites in Norfolk and Suffolk. Scientists said the infections were most likely to have been the result of spores from the fungus being blown across from mainland Europe.
But questions are being asked whether this is the case for infections recorded in places such as South Wales, Yorkshire and Northumberland.
RSPB forestry officer Nick Phillips called on the government to "keep the bigger picture in mind when it comes to drawing up a plan of action at the Cobra meeting".
"This isn't just about wind - science tells us human movement of plants and plant material is a key way this fungus has spread across Europe," he said.
"And this isn't just about Chalara - there's a long list of other tree diseases and non-native species that are already on our shores.
"We're a European island nation with strong international trading links. What we need now is a carefully considered response to minimise any further collateral damage to our trees and wildlife."
The most visible sign that a tree is infected with Chalara ash dieback is bleeding sores and cankers on the bark, and discolouration of the underlying sapwood.
The sores often surround branches in the infected area of the tree, causing the dieback of shoots, twigs, branches and smaller stems.
The disease has also been shown to infect ash tree leaves, appearing as blemishes.
There are numerous other diseases that display similar symptoms, making it difficult to identify for most people.
The Forestry Commission has issued guidance on how to identify the disease.
Source: http://www.bbc.co.uk/news/science-environment-20253767#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa
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