What is Acute Oak Decline?

Guides Pests and Diseases

27th February 2020 | Info

Acute Oak Decline

Common name: Acute Oak Decline 

Scientific name: None 

Trees Affected: English Oak and Sessile Oak. 

Areas affected in the UK: Southern England and Wales

So, what is Acute Oak Decline?

Acute Oak Decline is not a disease, but instead a combination of factors that lead to a tree becoming stressed to the point where it reaches a point of decline.  

Environmental factors such as soil condition, waterlogging and pollution cause a tree to become stressed which then invites secondary pests and diseases such as insects, fungi and bacteria to enter the tree, pushing it into decline.  

It is only over the past 20 years or so that Acute Oak Decline has been observed in the UK. However, it has been prevalent across Europe for hundreds of years.  

The Symptoms

Typically, the symptoms of Acute Oak Decline mirror those to a tree’s typical response to stress and include: 

  • General thinning of the crown – this is because an affected tree struggles to take up water. It can also be very sudden.
  • Bleeding stems that stop and start – have the appearance of dark, wet, ‘weeping’, patches.
  • Dark liquid seeping through cracks in bark – quite often will run down trunks too.  

[Left: Healthy Oakbark]                               [Right: Acute Oak Decline affected bark]

If a tree goes through a period of sustained and severe stress, then it will reach a point at which it no longer has the energy to cope with certain environmental factors.  

The Impact

As we are all currently aware, global warming and climate change are becoming an increasing issue that is beginning to impact our day-to-day lives – but it also has an impact on our trees. 

Acute Oak Decline isn’t a disease, so it doesn’t technically spread; however, due to climate change causing environmental differentiation, it is not guaranteed how this type of decline will react. What we do know, however, is that it will contribute/worsen certain environmental changes which ultimately will impact the number of oak trees affected.  

For example, if we have a period where there is sustained rainfall which causes the waterlogging of soil (more so than usual!), then some Oaks (particularly more mature ones) will struggle to adjust to the changes, become stressed and ultimately be pushed into decline. 

An ideal action that we can take to help combat Acute Oak Decline is to plant more oak trees, specifically in areas where it is known that they can naturally regenerate better.  

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