During National Plant Health Week 2024, our panel of experts from the Forestry Commission, Forest Research, Royal Botanic Gardens, Kew and Observatree led a live Tree Health Clinic Q&A on X (formerly Twitter) to answer your questions and offer advice about tree health.
What can I do to help minimise the spread of tree pests and diseases in my woodland?
Be vigilant, know the signs and symptoms of key pests and diseases. Spotting things early is key - find information on priority pests and diseases in the UK.
Matt
Timing forest works to avoid the worst weather and ground conditions is important to avoid the movement of soil associated and waterborne pests. Also aim to focus movements around the forest on stoned and drained tracks where possible.
Jonathan
Prevention is always better than cure. Never assume biosecurity threats aren't present, and remember to follow our 3 calls to action: Arrive Clean, Keep it Clean and Leave Clean. Find out how to prevent tree pests and diseases.
Emma
Removing invasive non-native plant species is a great idea as in addition to being problems themselves they can also be hosts for serious tree pests and diseases. For example, Rhododendron ponticum is an important host for highly-damaging Phytophthora ramorum.
Forestry Commission offer grants to assist in its removal - contact your local Woodland Officer for more information.
Barnaby
Is there evidence that more species-diverse forests are more resilient to new diseases? Would ancient woodlands or more recently established forests be more or less at risk?
Many pests and pathogens are fairly species-specific (e.g. ash dieback, oak processionary moth). So having a diverse portfolio of tree species helps resilience. Whether this needs to be at the level of a woodland or a landscape depends on your management objectives.
Richard
There is evidence that increased forest diversity reduces the risk. It is difficult to say which would be more or less at risk as challenges can be different. Sourcing stock from a reputable source is very important as diseases can easily be introduced to a site.
Caroline
There is lots of evidence for this e.g. monocultures of one crop can build up large numbers of a specific pest, which would be diluted in a forest with multiple species. Both ancient and newly planted woodland are at risk, especially when the trees involved are stressed.
Jonathan
The risk for ancient woodlands or more recently established forests is often the same when faced with an exotic pest or disease that they have not co-evolved with - ash dieback is a good example.
Barnaby
What will be the state of UK native trees by 2050 if we don't change our management practices?
An influx of pests and pathogens means that one by one our native tree species are becoming unavailable for planting. We need to (1) bolster biosecurity (2) increase the number of non-natives planted (3) breed our native species for resistance.
Richard
With proactive changes the outlook could be optimistic. By embracing sustainable forestry, biodiversity conservation, and climate and pest resilient strategies, we can foster healthier woodland ecosystems and ensure the vitality of our native tree species for the future.
Emma
This open access paper provides a summary of the issues affecting forests in the next 50 years, well worth a look.
A narrow idea of native is likely to lead to fewer species to choose from for future woodland creation and enjoyment. Trees can adapt in place, and by migrating (slowly). We have the option to practice using European natives that would naturally spread with climate.
Jonathan
What is the biggest disease threat to UK trees that isn't here yet?
The unknowns, the ones we're not yet aware of.
Matt
One significant threat for UK trees is Xylella fastidiosa. This bacterium could impact a wide range of tree species if introduced, posing a risk to the country's woodlands and ecosystems. Vigilance and preventive measures are crucial.
Find more information about Xylella.
Emma
What is the most likely cause of stem dieback in a containerised Betula utilis subsp. jacquemontii?
Without more information it's difficult to be specific, but if it is a large specimen it could be the result of environmental stresses. In pot grown plants drought stress or over watering can cause dieback. Please report it using Tree Alert.
Caroline
A wide range of factors could cause a dieback, things that affect roots or flow of liquids through the tree are more likely. These could be pests, but other concerns like drought or winter damage etc. Record symptoms and report to Tree Alert.
Jonathan
Are there any rays of hope emerging at all in the research and monitoring of Ash dieback, e.g. many resistant trees?
The Living Ash Project has identified a number of ash trees that have survived in areas with high ash dieback incidence and collected grafts into a single location ready for seed production.
Lone ash trees can often stay more healthy because they are less exposed to spores of the ash dieback fungus. The fungus needs ash leaf litter to grow on, and this tends to be scarcer around solitary ash trees.
Richard
You can help with the rays of hope too! If ash dieback symptoms are common in your wood, keep an eye on healthy-looking trees and report them if they still look good in a few years time. Ash dieback reports are currently being collated.
Barnaby
A narrow idea of native is likely to lead to fewer species to choose from for future woodland creation and enjoyment. Trees can adapt in place, and by migrating (slowly). We have the option to practice using European natives that would naturally spread with climate.
Jonathan
Read more about the contribution of Observatree volunteers.
Matt
I’m planning to create a woodland, how can I plan it with the threat of pests and diseases in mind?
A stressed tree is more likely to succumb to problematic pests and diseases, select the right tree for the right site - and bear in mind predicted future climate.
Matt
Focus on giving the trees the opportunity to grow as healthily as possible to resist pests. Learn about your soils to plant appropriate species, choose a quality nursery, then handle and plant the trees with care and avoiding frost and drought to get things off to the best start.
In terms of planning, don’t put all your eggs in one basket. Choose a manageable number of different trees species to dilute the threat of one pest being able to damage the woodland significantly. Make sure to plan ongoing maintenance and management to keep your woodland healthy.
Jonathan
Are regulations to safeguard UK forestry and horticulture against imported diseases and pests in harmony with the intention to identify/develop/encourage tree and plant species nationally and internationally which have developed resistance against (other) diseases and pests?
We have plant quarantine centres at Kew Gardens and Forest Research that allow plants of particular interest for research to be brought into Britain by our scientists. Where necessary, these may be released if they pass stringent plant health checks
Richard
There’s a healthy conflict required to balance these needs. Regulation appropriately assesses environmental impact of novel tree species use, & controls help prevent pest introductions and movement. We proactively advocate woodland creation with future suitable species.
Innovation is being proactively encouraged through species and provenance trials across the UK such as the Future Trees Trust, the Tree Production Innovation Fund and the Woodland Trust.
Jonathan
Is there funding available for tackling tree pests and diseases in England?
Depending on the pest or disease, and the area of the country your woodland is in, you could apply for funding through the Tree Health Pilot or Tree Health Grant.
Jonathan
If you are unfortunate and have been affected by Phytophthora ramorum, there are grants to assist removal of rhododendron and restocking your wood after removing infected trees. Take a look at section 10 of the woodland grants and incentives table.
Barnaby
Thank you for all your questions, and to our experts for sharing their knowledge and advice. For additional information, look at our GOV.UK pages about how biosecurity can prevent the introduction and spread of tree pests and diseases, and read our summary guide to managing tree pests and diseases.
