Tree Health: Acute Oak Decline (AOD)

Acute Oak Decline (AOD) is a condition known to be affecting several thousand oak trees, mostly across East Anglia, the Midlands and Southern England as far west as Somerset. It affects both of Great Britain’s native oak species: Pedunculate Oak (Quercus Robur) and Sessile Oak (Quercus Petraea); as well as other species of oak.

How to recognise the problem

AOD is characterised visually by oozing of dark fluid from cracks in the bark, rapid decline of the tree, and tree mortality. Death of affected trees can occur within four or five years of symptoms first becoming visible.

Many affected trees also have characteristic D-shaped exit holes of the buprestid, or oak jewel beetle, in the bark.

Treatment and management

The Forestry Commission is carrying out research into the condition, including trying to identify a link between the disease and the presence of the oak jewel beetle.

Generally, they advise us to leave infected trees where they are and monitor them, unless there are any immediate concerns about safety.  If possible, put a cordon round the affected trees to prevent access.  Try not to touch the bleeds on the trunk as this may transfer infection to other trees.  If only a few individual specimens are affected, it may be sensible to fell and destroy infected individual trees to keep the infection rate down, and reduce the chance of infecting healthy trees.

The Forestry Commission also says:

“We encourage people who work in or visit areas with affected oak trees to help us limit the spread of the condition by not touching affected trees if possible, cleaning their footwear between woodland visits, disinfecting tools after working on trees in affected areas, and not taking any plant material such as leaves and sticks out of affected woodlands.”

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