Tree health experts will join government and industry officials later for a summit on ash dieback.
The meeting, to be be chaired by Environment Secretary Owen Paterson, will assess the extent of the disease and what can be done to tackle it.
To date, dieback has been confirmed at 82 sites, with woodlands in Norfolk, Suffolk, Kent and Essex among the worst affected.
On Tuesday the disease was reported at seven sites in Scotland.
Some scientists warn the outbreak has the potential to devastate the UK's population of 80 million ash trees.
The summit will consider the findings of a nationwide survey carried out by 500 Forestry Commission staff.
The data collected from 2,500 10km x 10km areas aim to identify how far the disease has spread, and will form the basis of discussions on what steps need to be taken to deal with the dieback outbreak.
In the meantime, the Commission has issued guidance on how to identify the disease.
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 case in the UK was recorded at a nursery in Buckinghamshire back in March 2012.
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.
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 broadleaf 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 ramsoms. 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.
Researchers said the affected trees in woodlands in Norfolk and Suffolk were likely to have become infected as a result of coming into contact with Chalara fraxinea spores that had been blown over from mainland Europe.
The majority of confirmed cases have been recorded at nurseries or sites where young ash trees had been recently planted.
The Horticultural Trades Association (HTA) has been critical of the government, saying it first alerted officials of the threat back in 2009.
On Monday, a nursery forced to destroy 50,000 ash trees after the disease was found in its tree stock said it was considering taking legal action against the government for failing to block imports sooner.
The official spokesman for the prime minister said the issue of compensating affected horticultural businesses would be "dealt with ultimately by the courts".
A Defra spokesman told BBC News that the decision to convene a Cobra meeting last week and hold Wednesday's emergency summit on Chalara ash dieback was to show that the government wanted to take action "and is taking the matter very seriously".
Woodland Trust policy director Hilary Allison, who will be attending the summit, said the discovery of dieback in UK woodlands was very worrying.
"Unfortunately, it is often the case that until a tragedy such as ash dieback becomes a reality, it is very difficult to impress upon people the importance of protecting the UK's trees and the need to enforce stricter controls to prevent new pests and diseases entering the country," she told BBC News.
She added: "The Woodland Trust is pleased that Defra has been listening to its call for an emergency summit on ash dieback, but we want to stress that this situation only serves to highlight the consequences of leaving decisions affecting the security of our woodland to the 11th hour."
Source: http://www.bbc.co.uk/news/science-environment-20219649#sa-ns_mchannel=rss&ns_source=PublicRSS20-sa
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