Walkers are being asked to avoid parts of the Chinese Gardens at Rivington as a long-term project to tackle a serious plant and tree disease gets under way.

United Utilities woodland experts have started the scheme to remove all the rhododendrons which are affected by the disease following an instruction from the Department for Environment, Food and Rural Affairs (Defra)

Although some areas will be cordoned off while the work takes place, visitors will still be able to walk along many of the paths.

The problem was first spotted earlier this year following tests by Defra at Rivington and some plants were removed.

But further samples have shown the disease, called Ramorum Blight, has affected many more areas and a total of 21 hectares will be removed within the next two years.

Nick Taylor, of United Utilities, said: "People will still be able to walk on many paths in the gardens, but we are asking everyone to please stay away from the areas which have been cordoned off.

"The disease will not make you ill and does not pose any threat to your health, but if someone walks through a cordoned off area they could spread the disease further afield via the spores on the soles of their shoes."

Woodland experts are tackling the problem by cutting down diseased plants and then burning the stumps to treat the remains. Replanting alternative plants will be carried out.

The water supply from the reservoirs at Rivington and Anglezarke will not be affected.

Ramorum Blight was first detected in parts of coastal California where it affected tanoak trees and was known as Sudden Oak Death.