Join the RHS today and support our charitable work
Free personalised gardening advice
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Join the RHS today and support our charity
I have forgotten my password
Register for free to receive our newsletters, add comments to blogs/articles and to save content.
See what events are on near you and browse your bookmarked pages.
Horse chestnut bleeding canker is a disease of the bark of horse chestnut. It causes cankers (bark infections) which bleed a dark or reddish brown sticky fluid.
Bleeding canker is an infection of the bark of horse chestnut by the bacterium Pseudomonas syringae pv. aesculi and two species of the fungus-like (Oomycete) organism Phytophthora, which causes the affected bark to bleed a dark sticky fluid.
It is specific to horse chestnuts and both the white flowered Aesculus hippocastanum and the red A. × carnea are affected.
Cankers can be seen at any time of year.
You may see the following symptoms:
The effect on the tree is variable. Some infections last for years, more or less stable, and with little effect on the crown. Others spread rapidly and cause crown thinning, die-back and even death of part or all of the tree.
There is no chemical control currently available.
Two species of the fungus-like (Oomycete) organism Phytophthora (P. cactorum and P. plurivora) have long been known to cause cankers (bark infections) in horse chestnut, though cases were relatively uncommon and confined mainly to southern England. But in recent years there has been a dramatic upsurge in cases of bleeding canker, in many parts of the UK, from which Phytophthora could not be detected. Recent work in the UK and the Netherlands has established that the bacterium Pseudomonas syringae pv. aesculi is the cause of these new cases.
The bleeding fluid is produced by the tree in response to the infection, which kills the inner bark, cambium and outer layers of wood, causing disruption to water and nutrient transport. If the canker girdles the stem, the stem dies.
Research on the bacterium is still in progress. It may require wounds to infect (which may include naturally occurring lenticels, or pores, in the bark) or might exist on plant surfaces and be spread by wind-blown rain. Phytophthora spreads in a similar way and also forms resting spores which can remain for long periods in the soil.
Bacterial cankerChestnut blightHorse chestnut leaf blotchHorse chestnut leaf-mining mothHorse chestnut scalePhytophthora bleeding cankerPhytophthora ramorum and P. kernoviaePhytophthora root rotResearch by Forest Research into bleeding canker of horse chestnutWhy has my tree or shrub died?
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
Register for the site or sign in to share your experiences on this topic and seek advice from our community of gardeners.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.