New advice for woodland owners worried that their oak trees might be suffering from acute oak decline disease has been published by the Forestry Commission.

Symptoms of acute oak decline include dark fluid bleeding from splits in the bark on tree trunks, and as affected trees approach death there is a notable deterioration of the canopy, or tree tops, and ‘dieback’ of the branches. The condition can kill a tree in as little as four or five years, and it has been found affecting hundreds of trees across central and south-east England and parts of Wales.

Scientists from Forest Research, the scientific research arm of the Forestry Commission, have discovered a previously unknown bacterium which they believe is playing a key role. They are continuing investigations to obtain a better understanding of the disease, how it spreads, and what other factors might be involved. This information will form the basis of appropriate management strategies.

Meanwhile, in response to increasing public concern, they have written a guide, entitled ‘Managing Acute Oak Decline’, which gives advice, based on the knowledge they have gained so far, on how to recognise the disease, what to do about it, and how to minimise the risk of spreading it.

The guide stresses the importance of monitoring the progress of the disease, of limiting access to infected trees, and of disinfecting boots, vehicle wheels, machinery and equipment to help prevent its spread. If an infected tree is to be used for timber, the guide recommends the bark and sapwood be removed and burnt on site, and the logs cut into planks on site before being removed. Planks can be kiln dried at high temperatures to kill any remaining bacteria. It is unknown whether the disease affects timber quality, so caution is advised when deciding how the timber will be used.

The guide also advises against using acorns from infected sites when planting new oak trees, and explains how to report suspected cases to Forest Research’s Disease Diagnostic & Advisory Service.

The Forestry Commission is urging everyone who looks after oak trees to be vigilant and follow the advice in the guide, which was written by Dr Sandra Denman, Susan Kirk and Dr Joan Webber of Forest Research.