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New guidance on oak tree disease published

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 part 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
guidance in a Forstry Commission Practice Note 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 Practice Note 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 guidance 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 Practice Note, which was
written by Dr Sandra Denman, Susan Kirk and Dr Joan Webber of Forest

* “Managing Acute Oak Decline” is available to download free of charge
from Free paper copies can be ordered
from Forestry Commission Publications, PO Box 501, Leicester, LE94 0AA;
tel / fax: 0844 991 6500; e-mail:, quoting stock code

* Further information about the disease, including a map of its current
known distribution, is also available from

* Image couresty of The Forestry Commission

The oak is an iconic part the British countryside, and widely
celebrated in our art, literature, culture and history. It is an
important component of our natural environment, and produces some of the
world’s finest timber.

Acute oak decline should not be confused with “sudden oak death”
(SOD). Sudden oak death is a term used in North America for a disease
caused by a fungus-like pathogen called Phytophthora ramorum which has
killed millions of North American native oak and tanoak trees in
California and Oregon. Although it is also present in Great Britain, it
has mostly affected shrub species and heathland plants, and small
numbers of other tree species. Japanese larch trees in the West Country
have also been infected with SOD. Britain’s two native oak species,
pedunculate and sessile oak, have proved much less susceptible than
their American cousins, with only a handful being infected.

The terms “decline” and “dieback” are used by foresters and arborists
to describe conditions in which a number of damaging agents interact
with one another to weaken trees and bring about their deterioration,
and sometimes premature death. Decline and dieback can be either
‘chronic’ (slow and progressive) or ‘acute’ (rapid). Damaging agents
associated with decline include insects, diseases and extreme weather.
Healthy trees can usually withstand sporadic attacks by pests or
diseases when they occur singly, but often suffer significant damage if
they occur simultaneously or when the trees are stressed by other
factors, such as drought or flooding. Decline can also set in when
sustained attacks occur over a number of years in succession. In cases
of acute decline the trees experience a rapid deterioration in health,
sometimes dying within as few as four years of the onset of first
symptoms. Chronic decline occurs over many years. Oak trees can often
recover from chronic oak decline, particularly if there is a reduction
in the factors that cause it.

The Forestry Commission is the government department for forestry in
Great Britain. Forest Research is an arm of the Commission that
undertakes world-class scientific research and technical development
relevant to forestry. For further information visit

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