Bleeding canker of horse chestnut: Causal Agent

Bleeding canker of horse chestnut: Causal Agent

Phytophthora and Pseudomonas cause bleeding canker

Bleeding canker is a disease that affects horse chestnut trees (Aesculus hippocastanum). It was first reported in Britain in the 1970’s and today its incidence is dramatically increasing.

Before this current upsurge in incidence, affected trees were invariably found to be infected with one of two fungal pathogens: Phytopthora cactorum or Phytophthora citricola. However, recent DNA analysis of tissue taken from diseased trees has failed to detect any Phytophthora and analysis shows that Phytopthora is only responsible for bleeding canker in 5-10% of chestnut trees today.

An entirely different pathogen is now causing widespread disease in trees across Europe. Find out how Forest Research scientists identified this new pathogen as Pseudomonas syringae pathovar aesculi.

Researchers are now using molecular technology to characterise the pathogens biology.

Both Pseudomonas and Pseudomonas pathogens can cause similar symptoms: cankers on the stem, bleeding on the trunk and branches, occasional scaffold and crown die back. Find out more about the symptoms of horse chestnut bleeding canker.

Another pathogen that can cause bleeding cankers is Phytophthora ramorum. However, this pathogen has only been found in one specimen of horse chestnut in England. Unless a horse chestnut with bleeding cankers is located near to a source of P. ramorum - such as infected rhododendrons - then the likelihood of infection by P. ramorum is negligible. 

Despite this, P. ramorum must be taken seriously because it is a quarantine organism. If you suspect that a tree is suffering from P. ramorum infection, you should contact the Forestry Commission:

Plant Health Branch
Forestry Commission
Tel: 0131 314 6414