Massaria (S. platani)
This disease was noted in London 2009 by people who manage trees. London Plane trees were displaying large lesions, and branches would unexpectedly drop.
The cause of this condition is assumed to be spores from the fungal pathogen Splanchnonema platani which have been found to be associated with this disease.
The disease is prominent in mainland Europe in particular Germany, Austria, Netherlands and parts of France.
The spores can be identified under a microscope
Forest Research are establishing the following:
1 Whether the disease is native or introduced from mainland Europe
2 How it might behave in warmer climate
3 Other pathogens that may effect Plane trees.
Information taken from:- https://www.forestresearch.gov.uk/tools-and-resources/pest-and-disease-resources/massaria-disease/ 2018