Date lodged: 13 July 2018
To ask the Scottish Government what action is being taken to help manage the expansion of Phytophthora ramorum on larch trees in Scotland’s forests.
Answered by: Fergus Ewing 16 July 2018
The threat to our trees from pests and diseases is growing. Climate change, global travel and imported plants and wood can increase pests and diseases and their impacts.
First found in Scottish plant nurseries in 2002 and in gardens/parks in 2007, Phytophthora ramorum is causing extensive damage and mortality to larch trees and other plants in the wetter West of Scotland.
Particularly favourable weather conditions in 2012 led to a major surge in the extent and intensity of infection resulting in the designation of a ‘Management Zone’ centred on South West Scotland. An ongoing programme of progressive removal of infected larch within the Management Zone is underway.
Outwith the Management Zone, symptomatic trees and associated buffer areas of host species are systematically controlled through the use of Statutory Plant Health Notices (SPHN’s) which require removal of host species in those locations.
Forestry Commission Scotland undertakes a yearly aerial and ground surveillance programme, across Scotland to detect any intensification and expansion of symptomatic trees.
This intensive surveillance has ensured early identification of symptomatic trees and resultant control action with the aim of managing the pace of disease spread and intensity.
This year surveillance has shown that the extent and severity of symptomatic larch is significantly greater than seen over the past few years. However it is not yet at the level seen during the major outbreak in 2012-13.
Research evidence confirms that the wetter than average weather conditions experienced during August/September 2017, coupled with high inoculum levels have resulted in intensification in disease incidence this year. This effect is also being replicated in England and Wales.
Immediate action has been taken to commence the process of issuing the required Statutory Plant Health Notices, focussing on those furthest away from the currently heavily infected areas. Work is also underway with the sector, through the Scottish Tree Health Advisory Group and the Phytophthora Ramorum working group, to ensure that appropriate and proportionate management action is implemented. This work will include a full review of the Phytophthora Ramorum action plan to consider whether the approach identified within the plan is still appropriate.