Downlands Tree Surgery

Bleeding Canker of Horse Chestnut

  We are seeing more and more often Horse chestnut trees in decline. Long splits in the bark, crown and limb dieback and resinous bleeding on the trunk and branches are all too often the symptoms of Bleeding Canker of Horse Chestnut. According to the Forestry Commission this is not new and this type of symptom which was first reported in the 1970s, when the cause was found to be a fungal pathogen known as Phytophthora but in 2002 it was discovered that a completely different pathogen, a bacterium, Pseudomonas syringae pv aesculi, was responsible for the increase in these symptoms appearing on horse chestnut.

 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. 
• The impact on the environment can be particularly profound when large, mature trees are infected and disfigured by the disease. 

 Management of the disease

• At present there is no chemical treatment currently available to cure or slow the development of bleeding canker.
• If the bleeding lesions become so extensive that the entire trunk is girdled, the tree will inevitably die and have to be removed and disposed of appropriately.
• If major branches are infected and show dieback they should be removed, because recently-dead branches of horse chestnut may be susceptible to sudden fracture and drop as the wood dries out.
• Some trees may even survive for many years as disease progression can be very slow or even cease, and show signs of recovery as vigorous callus development occurs at the margins of wounds created when bark has been killed by the disease.

 However; according to an article in Horticulture Week it is not all doom and gloom; scientists have recently been able to decode the genome of a bacterium causing the canker. The genome sequence will allow scientists to determine which genes might be necessary for infection of a tree host so they can be targeted to manage the disease.

Information from the Forestry Commission 2009 and Horticulture Week 2010.

This disorder of Horse Chestnut is not to be confused with the Horse chestnut leaf miner which causes the leaves to curl and turn brown. That’ll be my next blog!