Promoting resilience of UK tree species to novel pests and pathogens: ecological and evolutionary solutions

Lead Research Organisation: SRUC
Department Name: Research


It has been made clear by examples such as Ash Dieback, that our trees face a serious threat from new diseases and pests. As trees are everywhere and are well-loved parts of our landscape, an important part of our economy and an essential part of our biodiversity, their loss has serious consequences. However, dealing with each new threat as it comes along is difficult, expensive and potentially futile as threats can evolve so much faster than their tree hosts. Also, tree health is not just about a single pest or disease, but about growing trees in the right place, about keeping population sizes up, about ensuring seedlings get a chance to grow and about allowing forests to change as the environment changes. So, in order to find a sustainable long-term strategy for keeping our trees healthy, we need to consider the range of real and potential threats that trees face and try to deal with these together. At the same time, we need to ask what is possible for changing the way we grow trees: how do we use trees now, what do we want from our trees in the future, and how much change are we willing to accept? By finding a middle ground, that brings together the best biological knowledge with a clear understanding of the possible ways to adapt, we can give our trees the best possible chance of withstanding new threats.

The most important part of finding a way to do this is bringing together many different groups of people, and different types of knowledge. A lot is known about many of our trees already, but usually this knowledge comes from unlinked, independent studies and rarely do results from one study tell us something about another, even for the same tree species. Much better coordination is needed. To show how this can be done, we aim to use the example of Scots pine, an important native tree species.

For Scots pine, we know of several serious threats that are either here or are likely to reach the UK soon. The remaining native Scots pine forests are small and fragmented, but we know that they are adapted to their local environments: so pine trees from one part of the country grow differently than those from another. There are large plantations of Scots pine in many parts of the UK - there is ten times as much planted as remains in the native forests - and these are often at much higher densities than are found in nature, and often alongside plantations of pines from other parts of the world. There is also a strong cultural attachment to the species; in many places pinewoods are being replanted and it is often used as a garden or amenity tree.

Our project aims to measure how variable and adaptable are the threats to Scots pine, to test how much variation there is in the tree species in resistance to these threats, and to find ways to get people involved in making healthier pine forests. By doing this we also aim to show how the same thing can be done for any other tree species, and to put in place the tools for getting it done. We will focus on three important threats to Scots pine - Dothistroma needle blight, the pinetree Lappet moth and pine pitch canker. We will bring together a group of scientists - specialists in ecology, tree genetics, forest pathology, plant biochemistry, fungal ecology and evolution and social science - who will work together on the same, carefully chosen pine trees. This work will tell us how much the UK Scots pine population varies and how much it can change from generation to generation; how populations of the threats grow and change; and what can be done to make the pine forests we have more resilient. We will bring in lessons from crop agriculture, where similar problems have been faced for generations, and adapt these for trees and forests, that have much longer lifespans. Finally, by talking to people who work with and use trees, and the general public, we will find ways to use this information to make things change on the ground.

Technical Summary

The project will take advantage of existing experimental resources that the consortium has been building for the past few years. These include living experiments (a reciprocal transplant experiment on 3 contrasting sites including 21 native provenances; a glasshouse provenance-progeny trial; field provenance-progeny and provenance trials) and genetic and genomic resources (a large database of mutations across the Scots pine genome and capability for high-throughput genotyping; reference genome for Dothistroma; genetic markers for Dothistroma and pine tree Lappet moth). These existing resources will be made available to the project at no cost.

We will assess distribution and variation in the threat organisms using surveys and genotyping, and study pathogen evolution by characterising genetic changes in samples from different populations. We will assess variation in the host using population genomics (high-density genotyping of samples from multiple populations in trials) and quantitative genetics (analysis of variation in phenotypic traits and extended phenotype - resistance, phenology, morphology, needle chemistry, needle endophyte community). Data from the biological studies will be unified in a spatially-structured database and used, with data on distribution, density and regeneration rates to model the introduction and spread of threat organisms and their interaction with a variable pine population. The models will be used to test scenarios for management change that emerge from stakeholder interactions.

We will use workshops, semi-structured interviews and focus groups with stakeholders (identified through stakeholder analysis) to identify, test and refine options for building resilient pine populations. This will be a dynamic process, with ongoing interaction between natural and social scientists in the consortium, and with stakeholders. Finally, we will create a template for extending the analysis to other tree species.

Planned Impact

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Description Natural forests are important places where people spent time for recreation and have a positive impact on our wellbeing. The long term quality of these forests is crucial and understanding the effect of our management decisions will help us in maintain healthy natural forests. For this research project we have looked at the Pine fungal pathogen 'Dothistroma septosporum', which is responsible for Pine Needle Blight disease and affects the health of most pines in the UK. Recently this disease has increased in frequency and severity in several Pine species across the UK. To understand the underlying dynamics of this outbreak we set out to study the structure r grouping of the pathogen on different host tree species (Lodgepole, Corsican and Scots Pine), management systems (plantations, nurseries and natural forest) and geographical areas in the UK and abroad (Canada). Furthermore we looked at the sensitivity of the pathogen from natural forests and nursery stock to widely used fungicides as their use in nurseries could affect resistance against these control measures. We have compared results of Dothistroma Needle Blight (DNB) with known (related) crop pathogens and shown that there is no fungicide sensitivity change in DNB in nurseries and forest collect samples. Based on our knowledge in agricultural systems where similar fungicides are used, nurseries should still be aware of fast and sudden changes in the pathogen sensitivity to fungicides.
Our work on the underlying structure of DNB showed three different races of DNB in Scotland associated with different host species (Lodgepole, Corsican and Scots Pine). The comparison with Canadian samples (where lodgepole pine originates) showed high similarity with the Lodgepole race and indicates introduction via this route. The race from southern UK (England) is very closely related to the Native Scottish Race and suggests an early introduction at some point. There wer also hybrids between SOuthern and NAtive individuals found based on genetic data. Based on these data, we suggest that dense plantations with non native species pose a potential threat to native tree forests in terms of pathogen outbreaks.
Exploitation Route Even though we did not find fungicide resistance in the nursery samples, similar fungicides and related pathogens have shown that a shift can take place within one growing season. It is therefor recommended to monitor Pine stock in nurseries regularly and carry out fungicide sensitivity tests. Also by using a mixture of fungicides rather than one specific fungicide will delay any possible resistance in the future.The findings will hopefully be taken up by tree nurseries in terms of fungicide application regimes to avoid resistance.
In terms of forest management, dense non native tree plantages that could be susceptible to pathogens and act as a reservoir should be avoided and instead locally adapted material should be used instead to avoid pathogen outbreaks and introduction of novel variants of existing pathogens.
Sectors Agriculture, Food and Drink,Environment

Description Data has contributed to excluding parts of the UK to grow certain tree species to avoid the spread of Dothistroma Needle blight. From our research it was found that the DNB epidemic was made up of three sub populations that differed in host species and genetic diversity. This probably means that there are different risks involved between these types. Furthermore it was advised that management of plantations trees was reconsidered as non native trees grown in high density monocultures also pose a risk for disease outbreaks that can easily spread to natural woods with related host species.
First Year Of Impact 2016
Sector Agriculture, Food and Drink,Environment
Impact Types Economic,Policy & public services

Description SRUC travel fund
Amount £500 (GBP)
Organisation Scotland's Rural College 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 04/2016
Description Fungicide resistance 
Organisation Alba Trees
Country United Kingdom 
Sector Private 
PI Contribution We collaborated with pine nurseries in different parts of Scotland and England on determining fungicide resitance. We attended meetings of several nurseries discussing fungicde use and resistance risks.
Collaborator Contribution They provided Dothistroma sampels from anonymous locations, furthermore there was a meeting and a tour around their facilities.
Impact Published paper showing no fungicide resitastance in nurseries compared to natural stands for any fungicide used.
Start Year 2015
Description BBC interview 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Invite to radio interview 'Drive Time' for BBC Scotland where project was explained in terms of what we would do and how we would achieve that and how it would help to manage tree health in the future. Interview was about 10 minutes long and aired prime time (around 17:00).
Year(s) Of Engagement Activity 2015
Description Popular press release in several local and national newpapers about the findings of our study which was additionally published in a scientific journal 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact We had our communication department write a popular press release that was picked up by several national and local newspapers such as the Scotsman. The article was an overview of our earlier publication in a scientific journal describing the risk of planting high density non native trees on disease outbreak in native natural stands.
Year(s) Of Engagement Activity 2018