Phytophthora – Working to keep our woods healthy
Phytophthora ramorum can attack and kill other trees so it’s necessary to take action and we are required by law to fell all Sweet Chestnut trees within 100m of each infected tree. This work is vital to the protection of not only Penrose but surrounding woodland in Cornwall.
Phytophthora ramorum at Penrose - October 2021
What has happened?
We were alerted earlier in the year by the Forestry Commission through site surveys followed by laboratory tests conducted by their Plant Health team that several Sweet Chestnut trees and Rhododendron species shrubs had been confirmed as infected by Phytophthora ramorum and Phytophthora kernoviae.
As a result, the FC issued a Statutory Plant Health Safety Notice (PHSN) to us as landowners, highlighting the areas affected and setting out legal requirements we are required to undertake as a result.
What is Phytophthora ramorum (Pr.)?
Phytophthora ramorum is a fungus-like pathogen which causes extensive damage and death in a wide range of trees and shrubs.
The disease is known in the USA as 'sudden oak death', but luckily it has little effect on British oak trees. However, Sweet Chestnut trees – which are widely grown in the UK are particularly susceptible and large numbers have been affected. It spreads quickly and easily via spores.
How did the trees at Penrose catch the disease?
The first confirmed case of phytophthora in the UK was in 2002. Since then, it’s likely that in many cases the disease has spread through spores released by infected trees, often passed to larch trees and Sweet Chestnut trees from Rhododendron ponticum, a common introduced species present in many British woodlands. Rhododendron is highly susceptible to the disease, and once infected it produces large numbers of spores. The evidence indicates that these spores can be spread over several miles in mists, air currents, watercourses and rain splash.
Where has Phytophthora been found at Penrose?
Phytophthora ramorum was identified in two separate locations at Penrose. Firstly, in Temple plantation woods which is located close to Penrose Hill car park. Secondly it was found at Bar Drive woods, this is the woodland that runs from the main Parkland alongside Loe Pool towards Loe Bar.
When native species become infected with Phytophthora they are killed by the disease, but they do not spread it to other plants. However, there are several species that play an active part in spreading the disease, including Sweet chestnut and rhododendron. It’s vital that we minimise the risk posed by these ‘carriers’ of Phytophthora.
What work do you have to complete by law to help stop the disease spreading?
Our aim is to eradicate the disease here to protect not only all the other woodland at Penrose, but also neighbouring and wider woodlands in Cornwall.
The Plant Health Safety Notice requires us to fell and remove the Rhododendron ponticum, along with the felling and removal of infected Sweet Chestnut trees and other nearby Sweet Chestnut trees within specified areas set out by the Forestry Commission.
Felled Chestnut trees and Rhododendron will be stump treated with Glyphoshate to prevent any regrowth and risk of re-infection. There are 40 mature trees affected, plus 140 smaller trees and coppice stools which require work over both areas affected.
The work is being completed as quickly as possible prior to minimise the amount of infected spore production the trees or shrubs can produce.
Isn’t there another option to felling the trees?
Unfortunately, no. We are required to complete the work by law under the terms of the SPHN, and crucially, the work will help minimise the spread of the disease any further. We appreciate that tree felling can be an emotive subject but by undertaking this work quickly, and with the longer term future of the Penrose woods in mind, we can do the work in a way to create opportunities benefitting wildlife and establishing new trees for the long term health of the woods.
So what will you be doing to benefit wildlife, and how will you protect the wildlife currently using the woods affected?
Removal of trees will create new open areas or glades, allowing sunlight to reach the ground and benefitting wildflowers, butterflies and other insects. Glades also provide ideal sites for us to plant new trees as part of this work and also for young trees to regenerate naturally – and we’ll be planting a variety of species as long-term replacements.
Working closely with the Forestry Commission, we have also been allowed to leave many Chestnut trees as standing deadwood. This process involves removal of the crown and stump treatment, but leaving the main stem of the tree to provide fantastic standing deadwood habitat for Owls, Woodpeckers, Birds, Bats, Fungi and invertebrates. These “Monoliths” can stand for decades proving incredibly rich and diverse habitats.
Other timber will be left on the ground, again to provide valuable long term ‘deadwood’ habitats as it starts to decompose
Bats are an incredibly rich and diverse part of the wildlife present at Penrose. To ensure that we take every precaution to protect these animals (which are protected by law) trees will be climbed and inspected for bats before any work is undertaken. If Bats are present the tree will be left for a period of time and re checked, as bats tend to change roosts every 2-3 days. Birds and other mammals which can move easily into neighbouring habitats will be less affected.
We have been liaising with Natural England and the Environment Agency regarding approvals to undertake work at or close to the Site of Special Scientific (SSSSI) at Loe Pool, and working closely with the Trusts own specialist conservation advisers. We have also undertaken an assessment of any archaeological features in the work areas, to ensure no features are damaged as a result of any work taking place.
What else are you doing for Trees and woodlands at Penrose?
Last year alone we planted over 1,000 trees in hedge creation / tree planting projects at Penrose and this winter we will be planting several thousand more in creating more new hedgerows with hedgerow trees. We are committed to creating more new woodlands at Penrose over the next few years, helping connect existing woodlands for the benefit of nature, carbon and people.
What will the woods look like afterwards?
Most of the areas we need to fell have a variety of tree species within them, so the removal of some Sweet Chestnut trees will only help bring light and life to the woodland floor, helping both flora and fauna. You will see more open glades, and plenty of timber left within the woods. We will try our upmost to leave branches in ‘windrows’ (lengths of intertwined branches which provide cover for birds and mammals)
The “Monolith” trees we will be leaving may look different within the woodland landscape initially, but the benefit to wildlife will be significant.
Will you sell or use any of the timber?
No, none of the timber will be extracted for firewood or sold commercially.
It’s possible we may convert some timber to build tree guards for tree planting at Penrose in the future.
Any movement of infected timber off site would require a Forestry Commission licence under the conditions of the Plant Heath Safety Notice.
Will the public footpaths and bridleways still be open?
The first phase or work near Penrose Hill will not affect access, but it will be necessary to close the public bridleway and footpath in Bar Drive woods temporarily during weekdays for safety reasons. This diversion will involve using the Higher Penrose bridleway route. Diversions and signs will be in place and these routes will be re-opened every weekend during the work to minimise disruption for visitors.
When will the work take place?
Our plan is for the Sweet Chestnut trees at Temple Plantation to be removed in early October 2021, taking approximately 1 week.
The second phase of work along Bar Drive will begin in mid-January 2022, taking approximately 4 weeks
Information signs regarding the work and any diversions to access routes will be placed at appropriate locations whilst the work is taking place.
Are these spores dangerous to humans, dogs or other wildlife?
Is there a chance it will spread further once you’ve done all the work? How will you know it’s all gone?
As the spores travel on the wind there is always a chance the disease will spread but by completing this work around the infected trees as quickly as possible, we will substantially reduce this risk. The only way to know that the disease has gone is when there are no new cases of trees displaying symptoms. The Forestry Commission will continue to undertake their ongoing monitoring
How can I help?
If you are visiting Penrose, you can help by staying on established bridleways and footpaths and keeping dogs under close control or on a lead. Thank you for your support.
If you have any further queries, please email Gregory.Cross@nationaltrust.org.uk
or telephone: 01326554082