A new disease of oak with symptoms of stem bleeding
What is acute oak decline?
A new disease condition of oak trees, Acute Oak Decline (AOD), is taking hold in Britain.
Mature oaks (>50 years old) are affected, and trees are characterised by symptoms of extensive stem bleeding. Both of Britain's native oak species, pedunculate oak (Quercus robur) and sessile oak (Q. petraea) are affected.
Dark fluid exudes from small cracks on the bark of stems and runs down the tree trunk.
The fluid may dry and cake on tree stems at certain times of the year.
In contrast to chronic oak decline, some of the affected trees die within 4 to 5 years of the onset of symptoms. In the early stages of the disease no changes in canopy health are noticed but as trees approach death canopies may be visibly thinner.
More information about symptoms
Research into acute oak decline
It is thought that bacteria cause AOD and tests are currently underway at Forest Research to identify these bacteria and confirm their role.
A similar condition also caused by bacteria has been reported on Mediterranean oaks in Spain.
Distribution of acute oak decline
Over the past three to four years there has been a growing number of reports on oak trees with symptoms of severe and extensive stem bleeding. The incidence of AOD in Britain is unquantified at this stage but estimates put the figure at a few thousand affected trees. The condition appears to be most prevalent in the Midlands and investigations to determine the extent of the disorder are underway.
More information about distribution within England and Wales
Reporting affected trees
Oak trees with symptoms of extensive bleeding may be reported to our Tree Health Diagnostic and Advisory service, using their standard report form.
Management of acute oak decline
Until the exact cause of AOD is known we can only offer management guidelines:
- Specific management advice
- Example of information notice to the public regarding stem bleeding of oak
See also:
Managing acute oak decline (PDF-1150K)
Forestry Commission Practice Note 15.
Further information
More detailed advice and recommendations for managing symptomatic trees, as well as more general information about the condition, is currently being produced as a Practice Note.
Information on other forms of oak decline.
Further enquiries should be addressed to:
Dr Sandra Denman
Forest Research
Forestry and Climate Change Centre
Alice Holt Lodge
Farnham
Surrey
GU10 4LH
Email: sandra.denman@forestry.gsi.gov.uk
Alternatively, enquires may be addressed to our Tree Health Diagnostic & Advisory Service at tree.doctor@forestry.gsi.gov.uk, tel 01420 22255.
