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Horse chestnut canker

This disease was first reported in the UK in the 1970s but was relatively uncommon until around five years ago.

What is horse chestnut canker?

A new strain of horse chestnut canker has seen cases surge across the UK, affecting trees of all ages and spanning from the south of England to the north and Scotland.


  • Extensive bleeding areas on tree stems
  • Occasional bleeding areas on scaffold branches


  • Linked to a bacterium species known as Pseudomonas syringae pv. aesculi
  • Mild winters and wet springs perhaps worsened symptoms in recent years


  • Large, mature trees can be disfigured by the disease
  • In severe cases large old trees can die
  • Younger trees are at greater risk and can die within 3-5 years

Report it

If you think you’ve spotted this disease please inform the Forestry Commission using the Tree Alert reporting tool. Three good-quality digital photographs are required to aid identification.

For more information visit the Forestry Commission.