NICOLA Spence has one of the most important roles in UK forestry. As the chief plant health officer, it’s her job to manage, prepare for and lead the eradication of tree pests and diseases when they arrive on our shores.

Here she sits down with Forestry Journal to discuss her work, how diseases are affecting tree planting targets and what lies ahead for the industry. 

Note: This article was published and the interview conducted before the arrivial of Pine Processionary Moth in the UK was confirmed. 

READ MORE: Pine Processionary Moth: Ban on imports of pine and cedar after pest discovered in UK

Forestry Journal: “Which pests and tree diseases are of most concern right now?”

Nicola Spence: “We have a continuous process of risk and horizon scanning, looking globally to see what pests and disease are emerging. On the Plant Health Risk Register, there are (currently) more than 1,200. We have contingency and emergency response plans for those that pose the highest risk. Right now, Xylella fastidiosa and emerald ash borer have the greatest potential to threaten UK trees. They are not yet present, but we have prioritised actions and regulations to control any import risk pathways, and for surveillance and to invest in research and preparedness.”

Forestry Journal: The spread of pests and diseases will inevitably impact on which tree species are favoured for planting in future.The spread of pests and diseases will inevitably impact on which tree species are favoured for planting in future.

FJ: “How is the threat posed by pest and disease shaping government’s approach to tree planting?”

NS: “Tree planting and plant health is a key priority for government. If we are to meet our net-zero carbon emission targets and halt the loss in biodiversity, we have to plant trees. We are planning to treble planting rates. Everything planted must be biosecure (whether sourced within the UK or from overseas) to mitigate those risks. It is also about resilience – ‘the right tree in the right place’ – so that it can be healthy and thrive and deliver the benefits in terms of carbon and biodiversity.” 

FJ: “Is the message that we need to increase productive forestry at home – not only to bring down timber imports, but also to reduce the risk of pests and diseases decimating our tree stocks – getting through to policy makers/government?”

NS: “Yes, absolutely. We would love to see increased productivity. We are providing various grants and initiatives, particularly with the nursery sector, to help increase capacity and innovate in the production of forest reproductive material. We have had one round of the Tree Production Innovation Fund (July 2021) and have launched another (March 2022) because we need to look at new ways of producing nursery material in a biosecure and productive way. 

 “It is unrealistic to think we are able to replace imports completely; we are a massive importer of timber and trees. However, we tightly regulate all tree imports and it is now difficult to import from some countries because of their disease status.  This creates a market opportunity for more forest reproductive material – and more timber – to be produced here, but I think it is unrealistic that we can be self-sufficient.”

FJ: “What tools could be at the forestry sector’s disposal beyond setting up demarcated areas and felling?”

NS: “There is a lot that we can suggest. First and foremost, managing woodlands and forests is so important. For some diseases, surveillance programmes proactively look for things considered a risk. Landowners could do this as well and report back to us (Tree Alert). Also, look at the choice of trees that are being planted, source trees from reputable suppliers (Plant Healthy certified). Take advice from the FC, particularly the woodland advisors and the various tools available for the planning of forests and woodlands.

Forestry Journal: Oriental chestnut gall wasp causes dieback of shoots and twigs, now widespread in sweet chestnut across south-east England. Oriental chestnut gall wasp causes dieback of shoots and twigs, now widespread in sweet chestnut across south-east England.

“Clearly, if we have a pest we can eradicate, we want to look at the robust actions we can take.  For established pests and disease, we work with landowners to try and manage the impacts and have an ongoing research programme that continually looks for new control methods, so that we do not necessarily have to fell the trees.

“For example, in 2015, we found the oriental chestnut gall wasp (affecting sweet chestnut) in Kent. It could have arrived through trade or, again, ‘on the wing’, Kent being a susceptible area. For the one finding on the first site, we initiated an eradication campaign. Through surveillance, we found several other sites. Investing in research into parasitoids (natural predators): the University of Newcastle found some native parasitoids. We have a relationship with colleagues in Italy, who manage this pest through a non-native parasitoid Torymus sinensis.  Last year, we went through the rigorous process of applying for permission to release them [Torymus sinensis] through ACRE. Last summer, we had fifteen releases at various sites in Kent and are monitoring progress to see whether this becomes a useful way of managing the pest.

“We are investing in other kinds of research like this. Natural biological means of suppressing a pest won’t eradicate it, but they will suppress and manage the impacts, so that we can then look at a longer-term solution.”

FJ:  “What actions are being taken to prevent pests and diseases coming to the UK on imported timber?”

NS: “We have regulatory tools to check imported wood products, including timber and wood packaging. Timber (as a trade) is well run and well regulated generally. In 2017, we issued a statutory notification for firewood (solid wood fuel). Generally it is a compliant industry with the wood being kiln-dried and inspected. 

“We have priority actions for wood-packaging associated with white goods, steel and slate. We have done surveillance, visiting stone and slate importers where goods might have come from China, where some of these wood-boring beetles reside. We helped different sectors clean up their wood-packaging use and it is something we continue to monitor very closely. The outbreak of Asian longhorn beetle (2012) that was successfully eradicated was definitely associated with wood packaging material from a nearby slate stone importer, so it shows that the risk pathway is there.”

FJ: “With Ips typographus (Ips) and Phytophthora pluvialis (Phyto. pl.) moving across the country, would you suggest that people reduce the ratio of trees affected by both in any woodland mixes they are planting right now?”

NS: “We must understand what the host risks are.  With Ips, the biggest risk is to stressed and windblown spruce trees. The area at most risk is the South East (Kent). Because the beetles can fly across the Channel, import controls are not relevant and there is no evidence to suggest they move in trade. We think it moves independently ‘on the wing’. 

Forestry Journal: Phytophthora pluvialis has been found on Western hemlock and Douglas fir in the UK.Phytophthora pluvialis has been found on Western hemlock and Douglas fir in the UK.

“Practically, land managers can manage their spruce to reduce the possibility of Ips finding those stressed trees and infesting them. We are supporting Ips ‘pilot’ grants to remove spruce from danger zones and then advising landowners to replant with something more suitable. We have practical measures and we are taking robust action to eradicate the pest at outbreak sites as well. Actually removing that host from areas that are vulnerable geographically will help reduce the risk to the rest of the UK at large. 

“With Phytophthora pluvialis, it is too soon to say.  We have found it on Western hemlock and Douglas fir. We are looking at ‘host’ studies as part of the research package (led by Dr Ana Pérez-Sierra at Forest Research) and this research will become part of our management advice when we understand more.”

FJ: “When might this research become available?”

NS: “We recently published a ‘New Disease Report’ (Plant Pathology Journal) on early findings for Phyto. pl. in the UK. Research is underway looking at the disease itself (distribution, biology, spread and origin) and will (probably) be published later this year along with advice to landowners and stakeholders. It is important to publish this quickly. We want other countries to start looking for it. This is the first report in Europe, but I wouldn’t be surprised if others have it and simply have not looked for or found it. Getting this information out will encourage other scientists and landowners to say ‘actually we need to start looking’. 

“A characteristic of Phytophthoras is that they like warm, moist conditions. In the UK, the west coast is exactly where you would expect to find it. It has been found previously in two other places: New Zealand and Oregon, USA. We are sharing some of our isolates with scientists in both places so that they can perform genotyping (genetic analysis) to try to work out possible origins of the strains we have here. This work is still underway and will form part of the work published later this year. Late autumn is realistic.”

READ MORE: Phytophthora Pluvialis now confirmed in every part of mainland Britain after Welsh find

FJ: “What would you consider the most likely source of Phytophthora pluvialis’ arrival/discovery in England? Is wind the most likely source, and why did it develop last year is it thought?

NS: “Phytophthora pluvialis has two types of spores: a motile zoospore (which can move in water) and an oogonia (sexual spore cell containing both male and female sexual structures). It is unlikely it blew across, because it has not been reported in continental Europe. It was first found on Western hemlock. We don’t really import Western hemlock, but it could be a historical import.  We are trying to piece together all the evidence, looking at all pathways, so that we can be very clear.”

FJ: “Would you consider it a possibility that Ips has been in the UK longer than first thought (first discovered in 2018)? Is there anything to indicate that it may have come in undetected on imported timber (with bark) destined for biomass?”

NS: “We don’t think so. We have done a lot of trapping and genetic analysis of the populations to find out where they come from. Forest Research entomologists are able to work out whether it is a first-year population or a breeding population (in situ for more than a year). In each case, we have found initial infestations, suggesting that they have come in that year. Trapping Ips using pheromone traps, we know where they are coming from, which direction and at what wind speeds and directions. Climate modelling the wind direction, we are confident Ips is coming in ‘on the wing’ across the Channel and not associated with imports.”

FJ: “Ips is moving northwards from Kent. Is there any way it can be stopped or contained so as to not reach Scotland’s forestry resource?”

NS: “We have trapped Ips in Kent and West Sussex, and as far as Essex, so we will continue to track that. The beetles are very small. I am not sure it will be viable for them to move ‘on the wing’ up to Scotland. Removing any windblown and damaged spruce from Kent (and proactively removing spruce from Kent) actually removes that host. If the pest establishes and the population builds up, there is more potential for it to move, but there is no evidence that it is spreading within the UK at the moment.

Forestry Journal: Asian longhorn beetle is an example of a pest that has been successfully eradicated in the UK, following an outbreak in 2012.Asian longhorn beetle is an example of a pest that has been successfully eradicated in the UK, following an outbreak in 2012.

"All the outbreaks detected to date are founding populations from Europe. We are trying to make sure the population does not build, as happened in France. They have not managed it, so the population builds and moves as it searches for a new forest to establish in. We are trying to break that cycle so that it cannot spread north.”

FJ: “Can you offer hope to the sector on pest and disease?

NS: “Absolutely. There is always a hope factor.”

Dr Spence highlights three points.

  • Processes for identifying risks: “We are constantly reviewing the regulations, surveillance, inspections, research and awareness ratings. The UK Plant Health Risk Group meets every month, reviewing threats and mitigating for the most significant threats and the recommendations are made to ministers at monthly Biosecurity meetings.”
  • Increased capacity: “In England and Wales, we have increased the number of Plant Health and Seeds Inspectors from around 100 to around 450, significantly increasing our inspection and surveillance capacity at ports and inland. Scotland’s Inspectorate has increased their number of inspectors and the FC has increased capacity in their Tree Health team.”
  • Research: “We are investing in research at universities and institutes. Forest Research and RBG Kew are collaborating within the new ‘Centre for Forest Protection’ virtual research hub. By identifying risk, taking action, investing in people on the ground (for surveillance and inspections) and investing in our research capability (new Holt Quarantine Laboratory), we have the capacity and facilities to deal with these threats.”

“It is important to say that we cannot eliminate all risk and it is everybody’s responsibility to share in identifying and managing risk. We are taking the lead as government, but we work with lots of stakeholders. It is our collective responsibility to protect our plants and trees for future generations to enjoy.”

FJ: “What can readers do to limit their impacts and to reduce the spread of pests and disease into the future?”

NS: “There are practical things we can all do. Everything from what we are buying (purchasing plants and trees from reputable nurseries, asking questions about their origins), where we are planting, how we are managing to our own behaviour around trees and woodlands and nurseries, making sure we do everything we can to keep pest and disease out.”

“There are actions that everybody can take when out and about in woodlands.

Biosecurity precautions:
• Disinfecting on arrival and before leaving (‘Boots, Bikes 
and Buggies: Keep it Clean’).
• Parking vehicles on hard-standing, although I know this 
is not always feasible.
• If people see a tree that they are worried or suspicious 
about, they can report it through the ‘Tree Alert’ online portal.  Forest Research assesses every report and if necessary, follows up with visit.”

@forestryjournal Forestry Journal went on the road this week #ICF #forestry #ClimateSmartForestry #glasgow #forestrylife #forestrymachines #forestryequipment #arb #HavaianasLivreDeCliches ♬ BORN FOR THIS - Foxxi

Dr Spence details some specific measures that could be implemented:
• Biosecurity boot-washing facilities.
• More visible signage. We want the public to have 
access to trees and woodlands, we just need to do everything we can to promote managing the risks.

For more information on the Woods into Management Forestry Innovation Funds and the Tree Production Innovation Fund, visit: