Video report by ITV Meridian's Tom Savvides
It's estimated that millions of trees will be chopped down across southern England because of ash dieback.
The disease was first spotted in the UK in 2012 and is now affecting swathes of woodlands across England.
Brighton and Hove City Council says more than 40,000 ash trees have been infected.
They say it will take years to bring the disease under control.
Work has started to remove up to 200 ash trees from Withdean Park to limit the spread of the fungus. The trees have been inspected and need to be removed due to their fragile and dangerous condition.
The disease is not only affecting ash trees in Brighton & Hove, it's also killing the species throughout the country. The worst affected areas are in the south and south east of England.
The symptoms of ash dieback first become visible during early June when the leaves are first emerging.
These show themselves as wilting, and dark discolouration on the leaves with elongated lesions developing on the smaller branches.
Eventually the whole crown will become infected with a characteristic 'crown die-back' developing over the next few years.
The disease spreads via spores caught in the wind from tiny mushrooms born from the main leaf stalk and has the ability to spread over a ten miles radius within one year.
Councillor Amy Heley, co-chair of the council's Environment, Transport & Sustainability committee, said: "Sadly, when ash trees have been infected with ash dieback, we have no alternative but to remove them.
"It's very upsetting for everyone, but our tree experts are working alongside other specialists to inspect our ash trees and look out for the signs of ash dieback and any other diseases too.
"When removing trees, we always ensure the effects are kept to an absolute minimum, especially when it comes to the natural habitats of our wildlife.
"Although the disease is having a devastating impact within the city and throughout the country, we are positively regenerating areas through careful planning.
With an estimated 75 to 80 per cent of ash trees throughout the country expected to die within the next five to ten years, our woodlands will look very different as a result of ash dieback infection.