By Stephen Eisenhammer

LONDON (Reuters) - Hundreds of staff from Britain's environmental agencies will survey the state of the country's ash trees this weekend in an attempt to control the spread of a deadly fungal disease that threatens to drive the species to extinction in the UK, a government crisis meeting decided on Friday.

The disease, which causes leaf loss and crown dieback, has already killed up to 90 percent of ash trees in parts of Denmark and has now been found in the wild in Britain.

The government banned imports of ash trees on Monday and has burned 100,000 trees to try and stop the spread of the disease known as Chalara fraxinea, or ash dieback.

Environment secretary, Owen Paterson, convened the crisis committee known as COBRA which meets to consider matters of national emergency.

"We're co-ordinating work across all of the main government departments... to make sure we're all doing everything we can to control the disease," he said.

"The urgent work that will happen this weekend will give us a much better picture of where the disease is; we can then target our efforts in those areas".

The task force will inspect the health of trees in 3,000 areas with the survey being completed by next week.

Ash trees are the third most prevalent tree in Britain, but their contribution to the woodland canopy is such that their loss could mean the end of many animal and plant habitats.

So far the disease has been found in 41 sites, mostly in East Anglia. (Editing by Steve Addison)