Exotic trees ‘threaten Scots pine forests’

Native Scottish pine species are at increased risk from disease when planted next to exotic pine tree species, according to new research.

Scientists from Scotland’s Rural College, SRUC, and Edinburgh University have discovered that the widespread planting of exotic species in dense forests has introduced new races of fungi and raised the threat posed to native Scots pine.

This follows an in-depth study to show how increased numbers of Corsican pine from Europe and Lodgepole pine from North America are heightening the risk of disease when planted next to native Scottish pine species.

SRUC plant researcher Peter Hoebe and Honorary Fellow Richard Ennos, from Edinburgh University, studied genes in fungi attacking pine needles from a number of locations, including forests around Aviemore, to determine the diversity and spread of the fungus dothistroma septosporum – the disease responsible for the current outbreak of dothistroma needle blight in native Caledonian Scots pine populations, as well as other species.

They have recommended the removal of exotic species from the vicinity of Caledonian pine populations and the restriction of movement of planting material to minimise its impact.

Dr Hoebe said: “This extensive study involved collecting hundreds of needles from forests around Scotland.

“In many cases, needle blight itself doesn’t necessarily kill the trees, but the loss of needles affects the growth of mainly young pines.

“While introducing exotic species to Scotland can sound very appealing, there are distinct risks involved.

“Planting exotic species related to native species reduces rather than enhances the resilience of forests to pathogens.”