Acute Oak Decline

This page details the nature, spread and management of a new disease affecting our Oak trees. There is a great deal of concern over the rapid spread of Acute Oak Decline (AOD) since it was first recorded in 2002; it has been likened to the devastating effect of Dutch Elm disease in the 1970's that caused the death of millions of Elm trees across England.

Oak moth

The Oak trees affected are of the Sessile and Pendunculate species, the ones most vulnerable are those aged over 50 years and located in the midlands and south of England. The symptoms are a bleeding from the trunk and branches, this is a dark sticky fluid that could be one of the means by which the disease spreads. In addition to this the tree canopy gradually thins over a 3 to 5 year period as the disease develops; the weakened condition of the tree makes them vunerable to other pests including the wood boring larvae of the buprestid beetle. A range of other opportunistic pests and diseases continue to exploit the trees as the AOD further develops.

The means by which the disease spreads is still very much open to debate by professional organisations. The theories range from humans spreading the bacterium by walking around infected and then clean woodlands to the cause being from squirrels, birds and even insects. An amount of pressure is being put on the government to fund research into AOD looking at how it spreads, if it can be prevented or minimised, the main concern at the moment is over the very fast rate of spread.

Oak moth larvae

Management of Oaks with suspected or diagnosed AOD centres on the control of potential spread. If you suspect your Oak tree may have this disease ask a qualified arborist like R J Trees to inspect the tree and advise you on the options. A solitary Oak with this condition will probably be left in situ and monitored for bleeding points and canopy thinning. In areas with several other Oak trees it may be necessary to fell the tree ensuring no timber or foliage is left as a mulch/woodchip and if required remaining material is burned on site. The presence of AOD should be reported to the Tree Health Diagnostic and Advisory Team via DEFRA and any replacement trees should not be Oaks.

Along with many other people we really hope that the research under way does lead to a solution to this disease and ensure the mighty oak remains an integral part of our British landscape.