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The phenomenon known as oak decline has been known in the UK for nearly one hundred years. However, in the last few years there has been an alarming increase in the number of trees affected by acute oak decline – a fast-acting problem thought to be caused by bacteria.
Oak decline. Copyright: RHS
Oak decline is a term that describes the deterioration of oak trees, in some cases eventually leading to death of the tree. A slow-acting phenomenon known as chronic oak decline or chronic oak die-back, thought to be due to an interaction between many different factors (pests, diseases and environmental conditions) has been known since the early part of the twentieth century.
In recent years another problem called acute oak decline has come to the fore. Thought to be caused by bacterial pathogens, this can lead to a rapid deterioration of affected trees.
Oak decline is unrelated to the disease known as sudden oak death which, despite its name, does not notably affect English oak trees.
You may see the following symptoms:
There are no chemicals available for the control of acute oak decline. However, it is recommended that any equipment used for the felling or pruning of affected trees is disinfected after use.
The above is a summary of the current recommendations given by the Forestry Commission (the full recommendations can be found at Forest Research).
Chronic oak decline has been known throughout Britain since the early twentieth century. It is thought to be caused by the interaction of a range of contributory factors, which are also likely to vary between sites. Factors that have been implicated include:
Acute oak decline has so far been found most commonly in south-east England, the Midlands and East Anglia, with recent cases on the Welsh border, and is still the subject of extensive investigation and research. A previous case of acute decline in the 1920s was thought to have been triggered by heavy infestations of the oak leaf-roller moth (Tortrix viridana). However, it appears that the recent outbreak is caused by bacterial pathogens. In many cases the wood-boring beetle Agrilus biguttatus is also present in the affected areas, and this could be one method by which the bacteria are spread from tree to tree (another could be rain-splash of bacteria in the fluid weeping from the bark cracks).
Honey fungusForest Research: acute oak declineForest Research: chronic oak declineForest Research: oak die-backOak gall waspsPhytophthora ramorum and P. kernoviaePhytophthora root rotPowdery mildewWhy has my tree or shrub died?
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