Cause for optimism in the fight against tree disease

Annika Perry and Stephen Cavers on their new research indicating that Scots pine could evolve to cope with Dosthistroma needle blight

Pests and diseases pose a serious threat to the UK’s forests, and the number of new pests and diseases is increasing [1]. Although much recent attention has focussed on threats to ash, nearly all of our main tree species face challenges [2]. In particular, pests and diseases of conifers have the potential to cause widespread damage - there is nearly 10 times more conifer than ash woodland in Britain [3]. Native Caledonian pinewood at Glen Affric, Scotland

However, whilst the threats are serious, our new research provides cause for optimism in the fight to protect at least one of these ecologically and economically important species, the Scots pine. One of only three conifer species native to Britain, Scots pine is threatened by a serious disease, known as Dothistroma needle blight.

Dothistroma needle blight is caused by a fungal pathogen called Dothistroma septosporum. Symptoms appear as red bands on needles and infection leads to premature needle death. In severe cases infection can result in slower growth or can even kill the tree.

Scots pine is the main tree species in the ancient Caledonian pinewoods, a highly valued native forest habitat found in the Highlands of Scotland. These pinewoods are beautiful and important in their own right, but are also essential habitats for rare mammals and birds, such as the pine marten and the capercaillie. Only 1% of the original native pinewoods remain and these fragments need careful protection. Dothistroma needle blight has been found in pine plantations across Britain, and has now been detected in Caledonian pinewoods.

Only 1% of the original native pinewoods remain and these fragments need careful protection.

cots pine infected with Dothistroma septosporum The results of our new work, published this month (open access) in the journal Plant Pathology [4], indicate that the species could evolve to cope with the threat from Dothistroma needle blight. In the study, young trees were grown together and tested for their resistance to disease: the trees were artificially infected with the pathogen in identical conditions, and their subsequent health was carefully followed. Many of the young trees became heavily infected, but many showed few symptoms. Importantly, resistance was similar in trees from the same family, meaning that the resistance trait can be passed on to future generations.

The results provide hope for the future of Caledonian pinewoods in the face of the threat from Dothistroma needle blight. Importantly, they also indicate that disease-tolerant varieties could be developed for this economically-valuable species.

Additional information

[1] Tree threats - the scale of the problem and what we are doing about it, Forestry Commission. http://www.forestry.gov.uk/forestry/infd-9cden2

[2] Tree pests and diseases by species, Forestry Commission. http://www.forestry.gov.uk/forestry/infd-9c9hhr

[3] Ash accounts for 157,000 ha of woodland area; conifers account for 1,308,000 ha of which pines account for 364,000 ha. Source: Forestry Statistics 2015, Forestry Commission. http://www.forestry.gov.uk/pdf/Ch1_Woodland_FS2015.pdf/$FILE/Ch1_Woodland_FS2015.pdf

[4] Substantial heritable variation for susceptibility to Dothistroma septosporum within populations of native British Scots pine (Pinus sylvestris). A Perry, W Wachowiak, A B Brown, R A Ennos, J E Cottrell and S Cavers. Plant Pathology. 2016. doi: 10.1111/ppa.12528

Staff page of Dr Stephen Cavers

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