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Forest Research home > Research > Protecting trees > Bleeding Canker of Horse Chestnut

Extent of the bleeding canker of horse chestnut problem

Percentage of horse chestnut trees surveyed in 2007 with symptoms of bleeding canker

The Forestry Commission undertook a survey in 2007 to assess how widely trees are affected. It confirmed that bleeding canker on horse chestnuts is now very widespread with around 49% of all the trees assessed showing symptoms to some degree. The extent of the disease also varies in different parts of Britain.

Percentage of horse chestnut trees surveyed in 2007 with symptoms of bleeding canker
RegionRural locationsUrban locations
Northeast 46% 33%
Northwest 54% 64%
Yorkshire and Humber 39% 37%
East Midlands 35% 47%
West Midlands 38% 87%
East of England 33% 59%
Southeast 79% 74%
London 47% 49%
Southwest 52% 58%
Wales 32% 41%
Scotland 34% 50%

Survey report (PDF-348K)

Forest Research scientists estimate some 35,000 to 50,000 trees are affected and probably a few thousands have already been felled as a result of the disease.

Horse chestnuts ranging from 10-15 year old vigorous saplings to large mature amenity trees can all be affected by the disorder.  Many are highly visible amenity trees in parks and public gardens, others form important features in avenues, historic gardens and landmarks such as the double avenue of horse chestnuts leading up to the prehistoric Avebury stone circle. 

In a detailed survey of around 230 horse chestnuts in Hampshire, about half were found to be suffering from bleeding canker (Straw and Green, unpublished data). A higher proportion of trees in towns and rural areas displayed symptoms compared with woodland trees, while slightly more red horse chestnuts (A. x  carnea) were affected compared with white flowered trees (A. hippocastanum). 

Reports indicate that not only common red and white horse chestnuts suffer from Pseudomonas bleeding canker.  The variety Aesculus hippocastanum 'Baumanii' appears to be extremely susceptible, and there have been occasional reports of Aesculus indica and A. flava with symptoms. An example of the rare hybrid chestnut, A. + dallimorei, has also been found to be susceptible to bleeding canker.