Thousands of trees are having to be cut down because of a fast-spreading disease, say Forestry England.
In the past five years, 115 hectares of larch trees have been felled because of Phytophthora Ramorum, with more needing to be cut to contain the spread.
Symptoms of the disease include areas of black "bleeding" on the trunk and withered and blackened leaves or needles - which lead to the dieback of the outer branches.
Woodland managers say they are fighting a losing battle with the disease being spread in a variety of ways from soil, water and wind.
In the Forest of Dean, Staple Edge and Danby Lodge have seen large-scale felling because of the disease.
Tom Brockington Operations Manager for Forestry England in Forest of Dean said: “Having to fell trees before they reach maturity because of disease is always a sad sight; it disrupts our forest plans and is something our professional Foresters never want to see.
"However, it is necessary, we must comply with Plant Health Notices to protect a woodland and the wider environment by containing a disease. It gives us chance to halt the spread, preserving as many trees as possible."
James Williams, who works in East Dean, says that larch and sweet chestnut trees are amongst the worst species affected.
"They in turn both spread it so it’s not just that they’re both killed by it but they spread the disease on, but there are potentially 150 different other species including garden plants and native species that can be infected."
Woodland visitors are being urged to take precautions to help stop the spread, with foresters saying that simple steps like cleaning your boots after a walk can make a huge difference.
"Largely, it is airborne, but it can be spread on hooves, feet, on tires and vehicles so we are taking steps to minimise the risk of transmission and implementation of biosecurity controls cleaning feet, washing down machinery that is used on-site and using a disinfectant wash," he added.