Bilberry plants at at the Roaches in Staffordshire have been infected by a rare fungal disease.
Phytophthora pseudosyringae has killed some plants near Roach End on the Roaches Estate, near Leek. The disease does not harm humans or animals.
People have been asked to help prevent the disease spreading by avoiding contact with the shrubs, although the area remains open to the public.
Managers have been preparing to treat the infected site.
Experts from the Peak District National Park Authority and Natural England are taking advice from scientists at the Food and Environment Research Agency as they work to deal with the disease.
Signs have been put up requesting people to avoid contact with bilberry plants, stay on the main footpaths and keep dogs on short leads.
Richard Campen, director of operations for the Peak District National Park Authority, said this particular fungus had only very recently been confirmed in Britain on bilberry plants.