Dr Glynn Percival and Jon Banks of Bartlett Trees describe the symptoms of Massaria disease in London Plane
Massaria disease of plane (Splanchnonema platani; syn. Massaria platani) is a fungal disease capable of killing the bark and cambium on the branches of London Plane, Platanus x hispanica, resulting in branch drop. The pathogen has been present in the UK for some time, with the disease recorded at Kew in 2003, Jersey in 2008 and Darlington in 2009, but until recently had not caused any major problems in the UK. Symptoms have mostly been observed across London and in some parts of Oxford in mature trees of at least 40 years old. At a recent London Tree Officers meeting it was estimated that 23% of trees located within the Royal Parks are infected.
Massaria is identified by a strip of dead bark starting at the base of the branch and stretching along the top. The width of the dead strip can vary but in most cases tapers to a distinct point. As the strip is located on the top of the branch, the disease is hard to see from ground level, however, if twigs, seed clusters and sometimes dead leaves
are observed on a branch these symptoms can be used as potential indicators of Massaria infection.
On smaller diameter branches 10 to 20cm in diameter, death can occur within a year. In fallen branches a distinctive darker V-shaped area of decay can be observed on a cross section. Branches of more than 20cm in diameter, however, may not display any of these symptoms prior to branch drop. On fallen limbs a white fungal mycelium may be present at the break point and a clearly zoned area of decay may be present.
The main problem posed by Massaria besides sudden branch breakage and potential loss of canopy shape is the fact that for public health and safety, full tree inspections need to be performed on average three times a year. This in turn leads to an increased maintenance cost on London Plane. No chemicals are registered to help in the management of this disease although the potential use of selective pruning, mulching and watering to reduce water stress within the tree has been discussed as a potential cultural management option.
Dr Glynn Percival is plant physiologist and technical support specialist for the Bartlett Tree Expert Company and manages its research and diagnostic laboratory at the University of Reading.
Jon Banks is a plant diagnostician for the Bartlett Tree Expert Company and is currently studying for his PhD.
