The health of one of South England’s most iconic trees is under growing threat.
Sweet chestnut trees (Castanea Sativa) are one of the UK’s most archetypical street trees, also commonly found in parks and woods up and down the country, providing food and habitat to a diverse range of wildlife.
The health of these trees is currently under threat from two increasingly devastating problems.
The oriental chestnut wasp (OCGW)
First recorded in Britain in 2015 in Kent and later in the same year in Hertfordshire. The trees affected were destroyed in an attempt to halt the species spreading, however by March 2020 the wasps had become fairly widespread in southeast England.
Symptoms of a tree affected by the OCGW are:
– Green, rose-coloured or red galls up to 4cm in diameter on the buds, leaves and petioles.
– Leaf distortion as a result of gall growth.
– Leaves affected by the gall wasp can either fall early or remain on the tree throughout winter.
A fungal disease that was first confirmed on sweet chestnut trees in the UK in 2011. The disease poses a significant threat to approximately 12,000 hectares of woodland which has sweet chestnuts as the majority tree species, predominantly located in southern England.
Symptoms of a tree infected by Chestnut Blight:
– The foliage wilts and dies as a result of girdling cankers lower down the stem.
– A striking contrast between green healthy and diseased orange bark on young stems. Underneath the bark buff-coloured fungal growth may be present.
– Cankers spread throughout the tree surface, killing the tree.
Young sweet chestnut trees may succumb to the disease within a year, meanwhile mature trees may take years before eventually dying.
The public are being encouraged to get involved in this project to help map the spread of both potential threats. Getting involved in the project is easy and does not require any specialist knowledge.
To get involved with the RHS project only a mere few steps are needed:
1. Make sure you know how to identify a sweet chestnut tree.
2. When you see a sweet chestnut, look for the above symptoms for either OCGW or chestnut blight.
3. Take photos of the tree and any visible symptoms.
4. Go to Tree Alert, the official government reporting tool for tree health and fill in a report.
Additionally, the public are also encouraged to report healthy trees, showing no signs or symptoms of OCGW or chestnut blight. Together with reports of infected trees, Forest Research scientists will be able to map the affected trees, as well as the proportion being affected.
The data will be used to create a national map of chestnut trees across Britain, an invaluable resource for targeting future surveillance efforts and the monitoring of new or emerging threats to all tree health.
Dr Jassy Drakulic, RHS plant pathologist, says: “The Check a Sweet Chestnut project is a vital tool in the fight to protect tree health and provides a great opportunity for members of the public to get involved in conservation efforts. By working together to record and monitor these trees we are helping safeguard Britain’s sweet chestnut trees for future generations to enjoy.”
The Check a Sweet Chestnut project previously ran in 2021, where records from citizen scientists mapped 350 sweet chestnut trees in Britain whereby undiscovered OCGW cases were recorded.
The organisations involved are launching the project to coincide with National Plant Health Week, taking place from 8th May to 14th May 2023.
The information collected by the public is invaluable in protecting the nations beautiful woodlands and wildlife.
All information recorded by the public on sweet chestnut trees will be published during National Tree Week in November 2023. For more information on the project please visit: www.rhs.org.uk/check-a-sweet-chestnut