Dothistroma needle blight (DNB) is a fungal disease affecting mainly pine species. The fungus affects the needles of the infected tree, which eventually shed. This can continue year on year and gradually weaken the tree, significantly reducing timber yields. It can also eventually lead to mortality.
DNB was first detected in Scottish forest tree nurseries in 2010. It has now been detected in over a quarter of Scotland’s 84 Caledonian Pinewood Inventory sites, although the impact of the disease in such sites currently appears to be modest.
Infected planting stock can lead to new infections in the wider environment. Once established, spread occurs via wind-borne movement during periods of damp weather conducive to fungal spore production. Movement of plant material, including infected needles on footwear, clothing, machinery and timber, can also potentially spread spores.
Dothistroma septosporum is a ‘quarantine pest’ for which statutory control actions are required if found in nurseries (but not in the wider environment). Following the 2010 and 2011 nursery infections, a two-year Forest Nursery Transition Scheme was initiated to support resilience building in that sector.
Annual nursery surveys are undertaken by Scottish Government HMU inspectors (with support from Forest Research). Annual surveys to determine the distribution and severity of DNB on the national forest estate have taken place since 2006.
Although no infections have been detected in Scottish forest tree nurseries since 2016, the disease remains a major cause of concern. Working with the nursery sector to increase their resilience to this and other tree health threats remains a key objective.