Phytophthora – Bleeding Canker of Horse Chestnut

by fse-admin - / 02.02.2016

Phytophthora – Bleeding Canker of Horse Chestnut

Phytophthora are a large group of pathogens that cause diseases in plants, including many species of tree. The name is derived from Greek and literally means ‘plant destroyer’ from phyto (plant) and phthora (destroyer).

How do I recognise it?

Trees which have been affected for some years may show crown symptoms such as thinning, reduction in leaf size and dieback.

In the early stages however, a dark reddish liquid can appear to be staining the bark of the trunk or on branches as if the tree is bleeding, as the name suggests.


The initial symptom of this disease is the appearance of droplets of rust coloured (or sometimes yellowy brown and black) sticky liquid from patches of bark or stems on infected trees.


There are no effective control measures for the disease itself since it is thought to spread in suitably mild and wet conditions in spring, when spores are produced and then spread via rain splash and aerial misting to above ground parts of the tree. This is where the germinate and infect the bark.

It may however be possible to reduce or remove the infection by cutting away the dead bark which should then be collected and burned to prevent further risk of infection.

Once an infected tree is identified, it should be surveyed regularly to ensure it doesn’t pose a risk.  Infected trees can survive for many years as progression of the disease is very slow and in some cases thought to cease altogether.  In the most advanced cases, the affected tree will need to be removed.

Did you know?

One of the most famous species of the genus is Phytophthora infestans, which attacks the leaves and stems of potato plants and causes the disease that contributed to the potato famine in Ireland in the mid 1800s.




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