Botanical Name: Pseudomonas syringae pathovar aesculi.

Diagnosis and Symptoms

The early symptoms tend to be limited to bleeding lesions with scattered drops of rusty-red, yellow-brown or almost black, gummy liquid oozing from small or large patches of dying bark on the stems or branches of infected trees.

Early in the year (spring) the exudate from bleeding patches is a dark colour but transparent. However, as the weather becomes warmer, bleeding from infected tissues becomes more copious and runs some way down the tree. At this time it is often a conspicuous rusty-colour and no longer transparent but cloudy or opaque. Under dry conditions during the summer, this exudate dries to leave a dark, brittle crust near the point of exit in the bark.

                                                                Dry exudate showing as a brittle crust             The dead inner bark showing mottling

Renewed bleeding may be seen later in the year, often in autumn. This suggests that pathogen activity is greatest under moist, mild conditions of spring and autumn.

After some months the centre of the bleeding bark patch may become cracked.
The inner bark (phloem) under the bleeding patches is usually necrotic or dead, with an orange-brown colour which is often clearly mottled or zoned.

In the latter stages of the disease possibly only parts of the crown will come into leaf and those leaves will be small, poorly formed and greenish yellow in colour compared to the leaves of a healthy tree.

Significance

The disease is widespread and of increasing incidence. It affects young and old trees alike.

Some trees will develop single or multiple bleeding cankers and still retain a healthy crown.

Some trees will develop multiple bleeding cankers and the areas of dead tissue will coalesce and extend until they encircle the entire trunk or branch resulting in the failure of that trunk or branch.

Some trees will survive for many years as the disease progression can be very slow or even cease. These trees may then show signs of recovery as vigorous callus (recovery growth) development occurs at the margins of wounds created where the bark has been killed.

                                 A young Horse Chestnut exhibiting multiple bleeding cankers

There is no proven chemical treatment currently available to cure or arrest the development of bleeding canker. However, trials of a chemical treatment are now taking place in Britain following some initially encouraging results in the Netherlands over the last few years.

Diseased trees and parts of trees which pose a risk of harm or injury, should be destroyed and not left around as they might act as reservoirs for the infection. Either burning or burying is probably the best method of disposal.

Summary