BAC-STOP

Iconic oak trees are dying from Acute Oak Decline (AOD)

Oak trees are important for the UK environment, landscape, economy, and culture. They produce timber, support woodland biodiversity and are culturally significant. Their unique features have made them a much-loved symbol of national identity.

However, they are threatened by an emerging disease, acute oak decline (AOD). Affected trees have long cracks in their bark which seep dark fluid. Beneath the cracks the stem tissues are diseased and rotting. The flow of water and essential nutrients is interrupted leading to the deterioration and potentially death of the tree. Thousands of oaks are affected in England, and the situation is worsening.

AOD is a complex disease with no single cause. Affected trees are weakened by unfavourable environmental conditions and colonised by beetles including the native oak jewel beetle, Agrilus biguttatus, and damaging bacteria like Brenneria goodwinii.

Find out more about Acute Oak Decline

Our research explored the combination of factors that leads to AOD

We studied disease development in trees weakened by environmental stress. Rain-exclusion shelters were constructed to mimic drought conditions and trees inoculated with beetle eggs and bacteria. Tree responses were monitored as the larvae hatched. To determine if the beetles transmit the bacteria, they were fed oak leaves coated with bacteria. Beetles were then washed and dissected to find out if the bacteria survived. To find out if the larvae affected the bacteria, larval chemicals were extracted by suspending beetle larvae in methanol. These chemicals were then added to bacterial growth media and the effects on growth and bacterial gene activity analysed. Interviews, questionnaires and training days were used to find out people’s attitudes to oak trees and options for the management of AOD.

To find out more about this project contact Sandra Denman.

Do you think you have spotted an oak tree with symptoms of Acute Oak Decline?

Please report it to Tree Alert

Want to find out more about tree diseases or check symptoms?

Download the BAC-STOP project’s easy to read factsheets on woodland tree diseases. The fact sheets cover the bacteria and host species, distribution and occurance of the disease. They also provide both text descriptions and photographs of symptoms. Finally, they provide advice on control measures and whether quarantine is required.

Full set of bacterial tree diseases factsheets
Watermark disease of willow
Shallow bark canker of walnut
Deep bark canker of walnut
Bark canker of alder
Acute oak decline

Project Partners

Updates from the BAC-STOP project

This is the updated map shows the distribution of locations affected by Acute Oak Decline (AOD), based on reports through the Forest Research Tree Alert system and research evidence. Unfortunately this year we received new most northerly records which are around Liverpool and Manchester, undoubtedly this is due to a warmer climate making this area more suitable for the Agrilus beetle. We have also noticed over the past year that there is an increase in severity of disease expression and there have been a number of tree deaths due to the combination of the damage to the conducting system done by the disease, coupled with the summer drought and extreme temperatures. Through the BPD we have also had enquiries and confirmed swab positives from some European countries.

The photos below show severe AOD stem weeping.

Meet the BAC-STOP Team