Fungal disease threatens London Plane trees
The London Tree Officers Association has issued the following warning:
"A worrying disease that attacks the capital’s most iconic tree has been confirmed in London. The disease, Massaria (Splanchnonema platani), was previously found only in Germany and Holland but has now been discovered in the UK. The disease affects London Plane trees (Platanus ‘x’ hispanica). Whilst London Planes are not native trees as they were introduced to the UK over 300 years ago, they now form an integral part of London’s landscape. The tree was such a significant feature of the capital that it became know as ‘London’ Plane. These are some of the tallest of the capital’s trees and one of the most planted."
According to the report, this fungal disease can rapidly decay branches and cause them to fall.
GSN is seeking advice from tree experts on how the managers of communal gardens can best address this problem. Meanwhile, if signs of this disease are appearing in your communal garden, please provide details in this discussion page.
Holly Smith
Editor and Publisher
October 10, 2011 | Garden Square News
Below is the latest briefing note on Massaria from the Forestry Commission, supplied by David Rose, Head of Tree Health Diagnostic & Advisory Service on November 17, 2011.
Massaria disease suspected in plane trees in England
Briefing
BACKGROUND:
London plane (Platanus x hispanica) is widely planted in the streets of our towns and cities in the south of England. The ‘London plane’ is usually reported as a hybrid between the Oriental plane (Platanus orientalis) and the American plane (P. occidentalis). This hybrid has grown well in urban environments, and Planes are notable for the way that they shed old bark and can withstand damage by air pollution, particularly soot.
Our Forest Research agency has confirmed an association of Massaria fungus (Splanchnonema platani, formerly known as Massaria platani) with dead and diseased tissue from plane trees at three locations in England during the past two years.
In addition, Dutch experts have confirmed massaria fungus associated with dead and diseased tissue taken from plane trees in the Royal Parks in London. The symptoms observed in the Royal Parks include lesions on the upper side of branches, branch dieback and branch drop (branches falling off the trees).
The fungus has usually been regarded an endophyte (a bacterium or fungus that lives within a plant without causing apparent disease), and as a weak parasite usually causing only minor damage, such as twig dieback. It has become common in warmer Mediterranean climates and the southern United States, although it is considered to be more widespread and damaging in the US than Europe. Frequently found on dead twigs and bark already killed by other organisms or non-living causes, massaria fungus has in recent years been reported causing rapid decay and branch death in some countries, such as Germany, Austria, The Netherlands and parts of France. It has been known to be present in England since 2003, when the Royal Botanic Gardens, Kew, discovered the tiny spore-producing structures produced by this fungus on fallen dead plane twigs. It was also found on a small, dead branch on a plane tree in Jersey in 2008, and again on fallen twigs in Darlington, County Durham in 2009.
Massaria fungus is not regulated as a quarantine organism because it has been described as an endophyte rather than a pathogen (a disease-causing organism). Scientists are investigating why the organism is now increasingly being associated with branch lesions, but the warming climate might be an important factor.
Forest Research scientists are now working to confirm whether the symptoms observed in the diseased plane trees in England are directly caused by the massaria fungus, or whether the fungus’s presence in the lesions is a typically opportunistic infection of tissue that has already been killed or damaged by another organism/s or cause.
Massaria fungus spores are easily spread long distances on the wind. In one notable case, viable spores were collected by a survey ship stationed over the Mid-Atlantic Ridge between the Caribbean Sea and North Africa, so it is no surprise to scientists that it could have spread from its Mediterranean heartland to Britain.
QUESTIONS AND ANSWERS
1. What does the future hold for the plane tree in Britain? Are we seeing the beginning of the end of them here?
It’s too early to predict what the long-term prospects might be, but widespread tree deaths are unlikely. The initial bark killing is followed either by death of the whole branch or, more commonly, by breakage of the affected branch. In Germany, Massaria disease of plane trees has become a significant economic problem for tree owners and municipalities, because the cost of tree safety inspection and tree care has increased dramatically because of the disease. The immediate need is for thorough research to understand the disease as well as possible with a view to formulating the best management advice for tree owners.
2. What can be done for diseased plane trees? Is there a cure?
There is no known cure for massaria disease. Remedial measures are limited to inspecting trees and removing those branches that are at a high risk of failure, and those whose failure would or could cause damage to property or injury to people.
3. What can be done to prevent or contain the disease?
The spores can be spread easily by the wind, so there is a limit to what can be done. Tree surgeons and others working with and around plane trees should clean and disinfectant their tools and boots etc after working on infected plane trees so that they do not spread the fungus to other trees by these means.
The less environmental stress a tree is exposed to, the better able it is to withstand attacks by pests and diseases. Therefore anyone planting plane trees should ensure that the site is well suited to them in terms of soil type, rainfall, sunshine hours, wind exposure and so on, and they should follow best practice in tree care.
4. Should landowners plant plane trees in the future?
Not enough is known about resistance to massaria damage that might be inherent in the different species of plane or the different varieties of London plane. Species choice is a decision for individual land managers to make based on their own objectives and priorities. In coming to a decision, we would advise them to consider the risks that their trees might develop the disease later in life and thereby incur costs associated with inspection and remedial pruning. If it proves possible to select for resistance to massaria amongst Britain’s population of plane trees it might be possible to produce planting stock that is less susceptible.
5. Where/whose were the trees with the positive samples tested by Forest Research?
These were in a private residential property in Holland Park, London, a tree owned by the Islington Borough Council in London, and one owned by Bristol City Council.
6. When will you have conclusive results from your own (FR) research?
We hope to have something within a few months, but it is difficult to predict a timescale for research of this kind, which is difficult and time-consuming.
7. Why has the fungus begun to cause more serious problems in recent years?
We don’t know yet. Its spread northwards from its usual location in the Mediterranean might be linked to climatic changes. We know, for example, that average winter temperatures in central Europe, including Britain, have been rising in recent years, with measurable effects on many living organisms. And episodes of Massaria colonisation are particularly correlated with stress in trees, especially drought stress However, more research is needed before we can fully understand this development.
December 2, 2011 | Garden Square News
It would be useful if Garden Square Committees could report cases of suspected Massaria and what led to the diagnosis. The next professional inspection of our 11 plane trees in Arundel & Ladbroke Gardens will be in late August or early September. However, . I read somewhere that the disease first showed itself in the crown., so it is possible that no symptoms will be detected until tree surgeons are actually working in the crowns of plane trees.
February 3, 2012 | susan lynn
Following an aerial survey of the 29 London plane trees (Platanus x hispanica) in Portman Square Garden, sadly Massaria platani has been identified on 15 of the trees.
Our current garden and tree contractors, Gavin Jones Ltd, advise that the disease is at varying stages of infection and have recommended that the infected branches be removed in line with current arboricultural best practice guidelines.
Thereafter it has been recommended that we carry out an aerial inspection of the trees twice a year and remove any evidence of infection at that time.
Westminster are aware of our problem and I believe they have been sympathetic to our treatment proposals.
We notified our counterparts in the surrounding area – Bryanston Square, Montagu Square, Manchester Square, Cadogan and Grosvenor Estates – to be on the look out for the disease in their garden squares.
If you have any further information you could pass onto us regarding treatment it would be greatly appreciated.
April 13, 2012 | Karen Wilson, The Portman Estate
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January 18, 2019 | Ruby