Cwmcarn Forest drive will close in November to remove 50,000 tonnes of diseased trees.
Natural Resources Wales (NRW) will fell trees with the highly infectious and untreatable Larch Disease across 400 acres of forestry.
The drive will be closed to make way for access to fell and remove the timber and NRW said the future of the visitor attraction is unceratain.
They said the forest drive will reopen if feasible but will require significant investment due to the felling and haulage operation.
Peter Cloke, from NRW, said: “Closing Forest Drive was a very difficult decision to make but was necessary to make sure the work to prevent further spread of this infectious tree disease is carried out safely.
“Although the drive itself will be closed, Cwmcarn Forest, the footpaths, mountain bike trails and its visitor centre are still open for business and is a fantastic place to visit for a day out.
“The replanting work after we have felled the trees will involve more diverse species and native trees like oak, birch and rowan. This will make it a better place to visit and more resilient to disease and the impacts of climate change in the future.”
Caerphilly County Borough Council said it will be business as usual at Cwmcarn Forest when the drive closes, with the campsite, visitor centre and mountain bike trails remaining open.
Cllr Ken James, Cabinet Member for Regeneration, Planning and Sustainable Development said: “While undoubtedly the felling of such a large area of the forest is very sad news, Cwmcarn Forest remains one of our key visitor destinations in the county borough, and we are determined to ensure that disruption while this work is undertaken is kept to an absolute minimum.”