Bleeding canker of horse chestnut

Infections by the gram-negative fluorescent bacterium Pseudomonas syringae pathovar aesculi are a new phenomenon, and have caused most of the bleeding cankers on horse chestnut that are now frequently seen in Britain.

[1] Infection of the tree through lenticels and leaf scars when inoculated in a study occurred most readily in the spring and summer.

The disease starts with local lesions, but becomes systematic when it affects the crown of the tree, usually after several years of infection.

Specific to horse chestnut trees, this pathogen infects the bark (cambium) around the trunk and main branches.

As it spreads, it cuts off the water supply to the crown; and when it completely encircles the trunk, the tree will die.

[4][6] The disease has risen markedly in the UK since 2003,[6] and now approximately one half of all horse chestnuts in Great Britain are affected and showing symptoms to some degree.

[5] The disease is spreading at an alarming rate in the Netherlands,[7] where one third of all horse chestnuts are affected to a greater or lesser extent.

[11] Heat Trial in Station Dordrecht Zuid: initially established success in the laboratory by Wageningen Plant Research.

They are desirable because they can tolerate many conditions including dry sandy soils, wet clays and chalk.