A fungus may be the cause of branch drop on plane trees
Plane trees (Platanus x hispanica) in Britain are reported to be suffering from Massaria disease, which causes large lesions on the upper surfaces of major branches and can cause branch drop. The cause is thought to be the fungus Splanchnonema platani (formerly called Massaria platani).
This resource page will help you to identify Massaria disease and the fungus that may cause it.
Details of the disease
In 2009 tree management teams in London began to notice large lesions and branch drop on the branches of plane trees. Similar symptoms had recently been seen on lesions of plane trees in mainland Europe, most notably in Germany, Austria, the Netherlands and parts of France.
Spores of the fungus Splanchnonema platani, formerly called Massaria platani, were found to be associated with the lesions. However it is not yet clear whether this is the primary cause of Massaria disease.
Identify the fungus
Forest Research has sequenced the DNA of spores isolated from tree lesions and confirmed S. platani to be present. We have also found:
- Characteristic brown, multi-septate pycnidiospores
- Occasionally characteristic ascospores
- The fungus seems to sporulate freely in Europe and spores are quite easy to identify under a microscope
- Until recently it was difficult to find sporulation on British samples
Forest Research is collecting fresh samples of lesions from planes trees to establish the cause of Massaria disease, and to see if lesions result from S. platani or subsequent infections with opportunistic basidiomycetes such as Auricularia spp.
Researchers are comparing cultures of S. platani with others from across Europe to establish if:
- Isolates from tree lesions in Britain are native and becoming more pathogenic because of climate change or changes in management
- S. platani was introduced from Europe on un-sterilised tools, infecting planting stock, or on the wind
- How it might behave in a warmer climate
- What other pathogens might affect plane trees
More information on this subject is available in:
Tubby, K. V. and Rose, D. R. (2009). Problems facing plane trees. Arboriculture Association Newsletter. 144, Spring. 18–19.