Management of Bleeding canker
We have a number of customers contact us for advice on the identification and management controls of Bleeding canker found on their Horse Chestnut trees. As a result of this we thought if would be helpful for our readers if we included some information and research we have in a blog, so we can refer them here.
Images of Bleeding Canker of Horse Chestnut (Pseudomonas syringae pv aesculi)
Identification and symptoms.
Bleeding Canker of Horse Chestnut (Pseudomonas syringae pv aesculi) is a disease that affects European horse chestnut trees (Aesculus hippocastanum) in Great Britain. It is characterised by the appearance of 'bleeding cankers', or lesions, on the stems (trunks) and branches. These cankers ooze, or bleed, dark fluid. In most cases diagnosed since the year 2000 the cause has been the bacterium Pseudomonas syringae pathovar aesculi.
Trees of all ages are affected and can die.
Cankers, or lesions, and bark cracks appear on the stem (trunk) and branches (see above).
Bleeding of dark fluid occurs from the cankers.
It can kill affected trees, although some do recover from infection, and some appear to be resistant to it.
Bleeding on the trunk and branches of horse chestnut in the UK is not a new phenomenon. This type of symptom was first reported in the 1970s, when the cause was found to be a fungal pathogen known as Phytophthora (Brasier and Strouts,1976). The same disorder had also been recognised in the USA much earlier in the 1930’s (Caroselli, 1953).
What trees are affected?
Trees of all ages have been affected by the recent disease upsurge. Young trees with a stem diameter of only 10cm (4 inches) have been found with advanced symptoms. However, the impact on the environment can be particularly profound when large, mature trees are infected and disfigured by the disease. If the disease is severe and the areas of bark which are killed are extensive, large trees can undoubtedly be killed.
However, younger trees (10- 30 years old) are at greater risk and can succumb to the disease in just a few years (3-5) as the smaller diameter of their trunks means that they can be girdled more quickly.
Management and control.
Confirming the cause of bleeding canker on horse chestnut is critical to any recommendations about effective management. Surveys are also recommended to assess the number and condition of affected trees.
There is no chemical treatment currently registered or approved for use in the UK to cure or arrest the development of bleeding canker caused by P. syringae pv aesculi. The following points should be borne in mind by managers of affected horse chestnut trees.
If cankering lesions become extensive the entire trunk can be girdled and the tree will inevitably die, and might have to be removed.
For public and property safety purposes, consider removing major branches that are infected and show dieback. Recently dead branches of horse chestnut can be susceptible to sudden fracture and drop as the wood dries out.
Trees with bleeding cankers on the trunk can still have healthy-looking crowns, and might not pose an immediate safety risk.
Some trees may survive for many years because disease progression can be very slow. They might even show signs of recovery, thanks to vigorous callus development at the margins of cankers when bark has been killed by the disease.
Removing affected trees unless they pose a safety hazard is unnecessary. It will not prevent disease spread on a site where some trees already show symptoms. Also, significant numbers of trees do recover.
Some trees are apparently resistant and never go on to develop symptoms despite exposure to the causative pathogens.
Find out more about specific recommendations on how to manage bleeding canker.
More-general biosecurity advice on preventing and minimising the incidence, spread and impact of tree diseases is available on the UK Government website.
Report a sighting
There is no need to report suspected cases of bleeding canker of horse chestnut. Managers of affected trees should follow the guidance given or consult a qualified arboriculturist.
Further reading a research can be found here.
If you are unsure on the identification or methods of control then we would be happy to discuss this with you. Please head over to our contacts page to get in touch.
