Felling call for exotic trees to protect native Scots forest

● Caledonian pines face bigger disease risk near imported species

Foreign pine species should be felled from forests where they grow near Scots pines to cut the threat of spreading potentially fatal diseases to native trees, according to experts.

A new study by scientists from Scotland’s Rural College (SRUC) and the University of Edinburgh (UOE) has shown that Scottish pine species have a higher risk of becoming infected when Corsican pines from Europe and lodgepole pines from North America are planted next to them.

Plant researcher Dr Peter Hoebe, from SRUC, and Professor Richard Ennos, an honorary fellow at the UOE, have found widespread planting of exotic species in dense forests has introduced new races of fungi and raised the danger of disease in indigenous pines.

They said these alien species should be removed from the vicinity of Caledonian pine populations and restrictions placed on movement of planting material to cut the chances of spreading afflictions such as Dothistroma needle blight, which is caused by a fungus.

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 dis-

0 Removing exotic species could help keep native pine forests more healthy tinct risks involved. Planting exotic species related to native species reduces rather than enhances the resilience of forests to pathogens.”

Dothistroma needle blight is caused by the fungus Dothistroma septosporum. It is currently attacking forests throughout Scotland, with the greatest impact in the north and north-east.

The disease affects a large range of conifers, but especially pines. The principal species currently infected in Scotland are Corsican, lodgepole and Scots pines.

The fungus affects the needles of an infected tree, causing them to drop off. This can continue year on year, gradually weakening the tree and significantly reducing timber yields. It can also eventually kill the tree.

Prof Ennos added: “Our extensive study sheds new light on the risks associated with the introduction of exotic species in general, and valuable insight into how the current needle blight outbreak might be better managed.”

Other tree diseases affecting Scottish forests include Phytophthora ramorum, which is killing larch trees and other plants, and Chalara dieback, a serious disease affecting ash.