Larch trees are coming under attack from Phytophthora ramorum which has led to the Forestry Commission joining forces with the forestry and timber sectors to eradicate the disease.
The species is so widespread they cover an area almost that of Edinburgh, Glasgow, Dundee and Aberdeen combined.
The threat to larch comes at a time when there is great challenge facing ash trees from the disease Chalara dieback of ash which has been identified at more than 500 sites across the UK and more than 100 in Scotland.
Phytophthora ramorum was first found in Dumfries & Galloway in 2010 but survey work carried out this spring suggests the disease has increased its range considerably in the area.
John Dougan, a conservator with Forestry Commission Scotland, said: "This is a worrying development and we are working with industry partners to manage its impact, both in terms of limiting its further spread and in dealing with the trees that have already been affected.
"There is a core area in Galloway Forest Park where it looks as if all larch has been infected and we are looking at how best to recover as much usable timber as possible.
"Beyond this core area, we are looking at taking further action to fell infected stands and those adjacent to it to try to minimise the further spread of the disease." Larch trees make up around 7% of the forest area in Galloway but about 6% of Scotland's 3.2 million acres of woodland.
The species can be easily spotted in Forestry Commission woodland as they turn golden in the autumn and winter months surrounded by the evergreen blanket of conifers.
Their timber is commonly used to make gates, garden furniture, decking and cladding for houses.
The disease can cause lesions, sometimes known as bleeding canker, which appear on the trees and exude black fluid from infected bark which often dries to a crust.
The inner bark under it is usually discoloured and dying.
The infection can spread easily over several miles in mists, air currents, watercourses and rainsplash and is known to attack a range of species other than larch, including rhododendron and blaeberry.
FCS says it is clear airborne spores are the most important factor in the current outbreak.
Additional survey work both on the ground and in the air is being carried out to determine the extent of the disease with actions to be agreed with the timber industry.
Environment and Climate Change Minister, Paul Wheelhouse, is aware of the situation and has asked to be kept informed of developments.
Mr Dougan said aerial surveys had also identified suspicious sites in other parts of Scotland, however it is thought the damage at these sites, most of which are well away from the main source of infection, could have been caused by canker, a more general collection of tree diseases, or squirrel or deer damage.
Jamie Farquhar, the Scottish manager of Confor, the body representing private woodland owners and managers and those working with timber products, said: "The forest industries are working with FCS to involve the entire sector in dealing with the impact of the disease.
"There will be increased felling activity which will involve not only the forest management and harvesting sectors, but also haulage and timber processors.
"It is an industry-wide approach that aims to hold up the spread of this serious disease, and mitigate its impact as much as possible."